Safe Harbor and Basis of Presentation Forward-Looking Statement Safe Harbor - This presentation includes "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. All of these forward-looking statements are based on estimates and assumptions made by our management that, although believed by us to be reasonable, are inherently uncertain. Examples of forward-looking statements include those related to net sales, gross profit, gross margins, capital expenditures and market share growth, as well as non-GAAP financial measures such as Adjusted EBITDA, the ratio of debt-to-Adjusted EBITDA, adjusted net income and base business sales, including any management expectations or outlook for fiscal 2018 and beyond. In addition, statements regarding potential acquisitions and future greenfield locations are forward-looking statements, as well as statements regarding the markets in which the Company operates and the potential for growth in the commercial, residential and repair and remodeling, or R&R, markets. Forward-looking statements involve risks and uncertainties, including, but not limited to, economic, competitive, governmental and technological factors outside of our control, that may cause our business, strategy or actual results to differ materially from the forward-looking statements. These risks and uncertainties may include, among other things: changes in the prices, margin, supply, and/or demand for products which we distribute; general economic and business conditions in the United States; the activities of competitors; changes in significant operating expenses; changes in the availability of capital and interest rates; adverse weather patterns or conditions; acts of cyber intrusion; variations in the performance of the financial markets, including the credit markets; and other factors described in the "Risk Factors" section in our Annual Report on Form 10-K for the fiscal year ended April 30, 2017, and in our other periodic reports filed with the SEC. In addition, the statements in this presentation are made as of September 13, 2017. We undertake no obligation to update any of the forward looking statements made herein, whether as a result of new information, future events, changes in expectation or otherwise. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to September 13, 2017. Use of Non-GAAP and Adjusted Financial Information - To supplement GAAP financial information, we use adjusted measures of operating results which are non-GAAP measures. This non-GAAP adjusted financial information is provided as additional information for investors. These adjusted results exclude certain costs, expenses, gains and losses, and we believe their exclusion can enhance an overall understanding of our past financial performance and also our prospects for the future. These adjustments to our GAAP results are made with the intent of providing both management and investors a more complete understanding of our operating performance by excluding non-recurring, infrequent or other non-cash charges that are not believed to be material to the ongoing performance of our business. The presentation of this additional information is not meant to be considered in isolation or as a substitute for GAAP measures of net income, diluted earnings per share or net cash provided by (used in) operating activities prepared in accordance with generally accepted accounting principles in the United States. 2

GMS at a Glance #1 North American specialty distributor of interior construction products (1) More than 205 branches across 42 states 14.6% market share in wallboard 16.7% market share in ceilings Other 23% Residential ~40% Steel Framing 16% Balanced mix of commercial new construction, commercial R&R, residential new construction and residential R&R Ceilings 15% Critical link between suppliers and highly fragmented customer base Wallboard 46% Commercial ~60% National scale drives purchasing advantages over peers while local expertise enhances service capabilities ($ in millions, April FYE) ($ in millions, April FYE) $2,412 One-stop-shop for the interior contractor with broad product offering of 20,000+ SKUs $2,319 $199 $198 $10 Since the 2016 IPO, GMS has continued to execute on its strategy Increased market share in wallboard by ~160 bps Executed 8 acquisitions and opened 5 new greenfields Increased LTM Q1 18 net sales by 29.8% and Adj. EBITDA by 41.1% compared to FY16 Expanded Adj. EBITDA margins by 70 bps compared to FY16 $1,162 $991 360bps FY-12 FY-13 FY-14 FY-15 FY-16 FY-17 LTM Q118 FY-12 FY-13 FY-14 FY-15 FY-16 FY-17 LTM Q1 18 480bps Net Sales Gross Margin (1) (2) (3) Based on sales of wallboard and ceilings. Wallboard share based on LTM 6/30/17 volume. Ceilings share based on LTM 6/30/17 sales. Net sales do not reflect net sales attributable to acquired entities for any period prior to their respective dates of acquisition. Breakdown based on FY2017 Net Sales. FY2015, FY2016, FY2017 and 1Q18 LTM Adj. EBITDA includes approximately $8.1 million, $12.1 million, $10.0 million and $3.6 million, respectively, from entities acquired in FY2015, FY2016, FY2017 and 1Q18 LTM respectively, for the period prior to their respective dates of acquisition. However, Adj. EBITDA margin and the 5.25-year CAGR exclude the impact of the entities acquired for the period prior to their respective dates of acquisition. For a reconciliation of Adj. EBITDA to Net Income (loss), the most directly comparable GAAP measure, see Appendix. 3 + % Margin (3) 3.3%5.0%6.4%6.7%7.4% 8.1% 8.1% CAGR: 41.1% (3) $150 $4 $195 $188 $114 $12 $138 $87 $8 $106 $57 $32 32.6% $1,858 32.7% + $1,570 31.9% $1,353 30.5% 29.7% 29.0% 29.0% Net Sales (2) Adjusted EBITDA (3) Net Sales Breakdown (LTM FY18 Q1) (2) GMS Overview

National Platform With Local Presence And Independent Brands GMS has an integrated national platform, but operates through over 50 local brands that are highly regarded in their markets Branch managers are empowered and incentivized to run operations like entrepreneurs within parameters of the overall business model - GMS’s model ensures customer and product decisions are made by the individual with the best local market knowledge GMS’s model generates significant economies of scale, while maintaining the high service levels, entrepreneurial culture, and the customer intimacy of a local business 4 Representative Local Brands GMS combines the benefits of national scale with a local “go-to-market” strategy

Product Overview Primarily consists of complementary interior construction products, including joint compound, finishing materials, tools and fasteners, safety products and EIFS (exterior insulation and finishing system) #1 Market Position Suspended ceiling systems primarily comprised of mineral fiber, ceiling tile and grid Architectural specialty ceilings systems Steel framing products for interior walls Sold into commercial applications, typically as part of a package with wallboard, ceilings and other products #1 Market Position Used to finish the interior walls and ceilings in residential, commercial and institutional construction projects Exterior wallboard Adhesives EIFS Insulation Joint compound and plaster Safety equipment Tools and fasteners Various types of wallboard including: 1/2 inch standard (residential), 5/8 inch fire rated (commercial), foil backed, lead lined, moisture resistant, mold resistant and vinyl covered Acoustical ceiling tiles (standard and architectural specialty) Clips Covered fiberglass Ceiling tile grid Hangers Drywall steel Flat stock Plastering steel Structural framing Studs and track 5 Products Description Other Products Steel Framing Ceilings Wallboard

A One-Stop-Shop for the Interior Contractor GMS Serves as a Critical Link Between Suppliers and a Highly Fragmented Customer Base - Specialty wallboard distributors lead the wallboard distribution channel with ~65% - Specialty distributors account for ~90% of ceilings distribution channel Steel Framing Fasteners Joint Compound Wallboard Ceilings Tools Safety Products Insulation (1) Based on management estimates. Highlighted boxes indicate channels in which GMS competes. 6 Other (~10%) Specialty Distributors (~90%) Big Box Retailers (~20%) Lumberyards (~15%) Specialty Distributors (~65%) Wallboard Ceilings Channel (1) Key manufacturers “One-stop-shop” for the Interior Contractor GMS sells a complementary and complete product offering to the interior contractor who installs wallboard, ceilings, steel framing and all the ancillary products needed to complete the job

Highly Attractive Industry Structure Number of U.S. suppliers declined from 12 in late 1990s to 7 today The top 4 represent ~76% of the market (1) Highly consolidated supplier base(2) Average price increase of ~3% annually since 2007 (3) GMS maintains a strong, long-standing relationship with the supplier of the leading ceiling tile brand, with exclusivity in many of GMS’s markets Other 4% 10% 26% 10% 13% 21% 16% Source: Management estimates. (1) (2) (3) Based on 2015 financials. Based on USG Corporation and Armstrong Ceilings public filings as of 2016 and management estimates. Based on USG Corporation’s public filings and management estimates. 7 Top 3 represent +95% Wallboard Ceilings Consolidated supplier base focused on price and margin optimization

Market Leader with Scale Advantages Market Leader with Significant Scale Advantages – #1 North American Distributor of Wallboard and Ceilings Differentiated Service Model Drives Market Leadership Multiple Levers to Drive Above-Market Growth – Market Share, Greenfields, M&A, Operating Leverage Capitalizing on Large, Diverse End Markets Poised for Continued Growth Entrepreneurial Culture with Dedicated Employees and Experienced Leadership Driving Superior Execution GMS Wallboard Market Share 14.6% 14.3% 13.1% 9.9% 9.4% 8.8% 8.6% (1) (2) (3) (4) CY2010 CY2011 CY2012 CY2013 CY2014 CY2015 CY2016 LTM Q2 CY2017 (1) Includes the wallboard volume from entities acquired in calendar 2014 assuming that the entities were acquired on January 1, 2014. Includes the wallboard volume from entities acquired in calendar 2015 assuming that the entities were acquired on January 1, 2015. Includes the wallboard volume from entities acquired in calendar 2016 assuming that the entities were acquired on January 1, 2016. Includes the wallboard volume from entities acquired in FY2016 and FY2017 assuming that the entities were acquired on April 1, 2016. (2) (3) (4) 9 11.1% ’10–’17 Q2 share gain: ~600 bps National Scale Combined With Local Expertise

Differentiated Service Model Drives Market Leadership reaching the end customer support, expertise, and sourcing entiated Weight And Delivery Requirements ce Model execution technology and equipment 10 Logistics Execution is Critical Given Reputation for best-in-class delivery Strong processes, sequenced loading, coordinated delivery, and leading Customized delivery plan and unique degree of quality control Superior Safety Track Record is Highly Valued by CustomersDiffer Servi Network of Regional Safety Managers Strict and consistent safety procedures Safety protocol critical to larger commercial contractor customers Approximately 600 Salespeople Helping Customers Succeed in the Market Place Deep technical expertise and knowledge of local markets Key intermediary for suppliers in Provides business development, bid Breadth of Product Availability Differentiates GMS from Smaller Competitors Ensures product availability Access to latest product innovations; significant customer for its top suppliers Leading ceiling tile line with exclusivity in certain markets GMS believes it sets the industry standard in product availability, customer support, delivery execution and safety; this differentiated service model has driven attractive gross profit margins

Best-in-Class Delivery Execution Drives Margin Distributing wallboard requires a high degree of logistics and service expertise due to: - Product characteristics: High weight to value ratio, easily damaged and cannot be left outside - Delivery requirements: Typically delivered with special equipment to a specific room often before or after normal business hours Allows for competitive differentiation and drives higher gross profit margins 1 2 3 4 5 Initial Job Site Inspection Sequenced Loading Process Customized Delivery Plan Coordinating Delivery Quality Control 11 Best-in-class delivery requires a very well trained, coordinated and motivated staff, along with strict and consistent safety procedures, technology and equipment

Multiple Levers to Drive Growth Continued Market Share Gains Greenfield Branch Openings Capitalize on “Other Products” Category Growth Opportunities $199 $198 CAGR: 41.1% $8 Strategic Acquisition Opportunities in Highly Fragmented Market Expanding in New and Existing Markets to Enhance Strategic Capabilities FY-12 % Margin (1) 3.3% FY-13 FY-14 FY-15 FY-16 FY-17 LTM Q118 5.0% 6.4% 6.7% 7.4% 8.1% 8.1% Well Diversified End Markets with Significant Room for Continued Expansion 14.6% 14.3% 13.1% 9.9% 8.6% Operating leverage Operational excellence (2)(3)(4)(5) CY2010 CY2011 CY2012 CY2013 CY201CY201CY2016 LTM Q2 4 5 CY2017 (1) FY2015, FY2016 and FY2017 PF Adj. EBITDA includes approximately $8.1 million, $12.1 million and $9.5 million, respectively, from entities acquired in FY2015, FY2016 and FY2017, respectively, for the period prior to their respective dates of acquisition. However, Adj. EBITDA margin and the 5-year CAGR exclude the impact of the entities acquired for the period prior to their respective dates of acquisition. For a reconciliation of Adj. EBITDA to Net Income (loss), the most directly comparable GAAP measure, see Appendix. Includes the wallboard volume from entities acquired in calendar 2014 assuming that the entities were acquired on January 1, 2014. Includes the wallboard volume from entities acquired in calendar 2015 assuming that the entities were acquired on January 1, 2015. Includes the wallboard volume from entities acquired in calendar 2016 assuming that the entities were acquired on January 1, 2016. Includes the wallboard volume from entities acquired in FY2016 and FY2017 assuming that the entities were acquired on April 1, 2016. (2) (3) (4) (5) 12 Margin Expansion (5) 11.1% 8.8%9.4% GMS Wallboard Market Share ’10–’17 Q2 share gain: ~600 bps Market Growth Strategic Acquisitions $150 $4 $195 $10 $188 $114 $12 $138 $87 $106 $57 $32 (1) Organic Growth Pro Forma Adjusted EBITDA (1) Strong track record of executing profitable growth strategy

Strong History of Market Share Gains Significant Competitive Advantages: GMS Wallboard Market Share Scale and leading market positions drive competitive advantage Breadth of product availability and access to leading brands and latest product innovations Highly trained workforce delivering differentiated service offering High degree of logistics capabilities and expertise, and best-in-class execution (4) 21.8% CY2016 14.3% 21.7% (3) CY2015 13.1% (2) 17.3% CY2014 11.1% Initiatives: Continue to expand retail showroom network within its branches Capitalize and expand on its national homebuilder relationships Continue to strengthen relationships with manufacturers and customers via GMS’s national sales expo and similar events Deliver the latest product innovations in order to continue to provide holistic solutions to its customers 14.8% 9.9% CY2013 17.3% CY2012 9.4% 2.4% 8% 8.8% CY2011 GMS Wallboard Volume Growth North American Wallboard Volume Growth (1) Source: Gypsum Association and GMS data. Includes the wallboard volume from entities acquired in FY2014 and FY2015 assuming that the entities were acquired on January 1, 2014. Includes the wallboard volume from entities acquired in FY2015 and FY2016 assuming that the entities were acquired on January 1, 2015. Includes the wallboard volume from entities acquired in FY2016 and FY2017 assuming that the entities were acquired on January 1, 2016. (2) (3) (4) 13 11.8% 2.6% 4.9% 8.4% 10.0% 0. Above Market Growth (1) Growth Drivers Proven history of growing faster than the market and gaining share

Attractive Acquirer with Significant Consolidation Opportunity Industry Structure: Large, highly fragmented industry comprised of hundreds of competitors Similar business operations enable efficient integration Acquisition Quarter Rationale Three branches with LTM sales of $24.5 million Further strengthens GMS’s leading presence in Michigan Founded in 1988 FY18 Q2 Aug 1, 2017 One branch with LTM sales of $11.7 million Expands existing presence in Hawaii Founded in 1974 Acquisition Strategy: Criteria: leading capabilities in targeted new markets / increase existing network density / enhance strategic capabilities Fit GMS culture and platform Deliver scale benefits Attractive purchase price multiples Dedicated M&A team FY17 Q4 Feb 1, 2017 One branch with LTM sales of $12.3 million Strategic entrance into northeastern Indiana Founded in 1984 FY17 Q3 Dec 5, 2016 Three branches with LTM Sales of $27.0 million Nice geographic fit with FY16 Q3 MI acquisition Founded in 1965 FY17 Q2 Oct 31, 2016 Robust Track Record: Fiscal 2017: ~$216mm LTM sales, 16 branches (1) Fiscal 2016: ~$209mm LTM sales, 25 branches (1) Fiscal 2015: ~$118mm LTM sales, 11 branches (1) Three branches with LTM Sales of $30.0 million Strategic entrance into south central Ohio Founded in 1996 FY17 Q2 Oct 3, 2016 Three branches with LTM Sales of $52.9 million Strategic entrance into south Florida Founded in 2008 FY17 Q2 Sept 1, 2016 Pipeline: Significant portion of the market is comprised of local, independent competitors representing significant opportunity Maintain active dialogue with many potential targets One branch with LTM Sales of $46.8 million Strategic entrance into the greater Philadelphia metropolitan area FY17 Q2 Aug 29, 2016 Founded in 1994 (1)Represents LTM sales of companies acquired during the fiscal year 14 Recent GMS Acquisitions Acquisition Strategy Employee-centric culture and industry track record position GMS to drive additional growth through acquisitions

Significant Opportunity to Further Expand the Platform GMS has a demonstrated history of successful expansion through greenfields and acquisitions GMS has limited or no presence in just under 40% of the top 100 MSAs in the U.S. Significant opportunity for share gains in new and existing markets over time Canada WA ME MT ND VT MN OR ID NH MA WI NY SD MI RI CT WY NJ PA IA NE NV OH DE DC MD UT IN IL WV CA KS VA CO KY MO NC TN AZ OK SC AR NM MS GA AL TX LA AK FL HI (1) GMS currently has limited or no branches in the areas identified as an MSA with limited or no GMS presence. There can be no assurance that GMS will be able to expand into any of these areas. Additionally, in the event GMS takes measures to expand into these areas, there can be no assurance that GMS will be successful, and any such expansion will be subject to several risks including those discussed under the heading “Risk Factors” in the Registration Statement that the Company has filed with the SEC for the offering to which this presentation relates. 15 Current GMS Branch MSA with limited or no GMS Presence(1) GMS Headquarters GMS has a significant opportunity to expand its geographic footprint in under-served and under-penetrated markets through greenfields and acquisitions

Large Specialty Distribution Market Opportunity North American market for distribution of wallboard, ceilings and complementary products generated $16 billion in net sales in the twelve months ended December 31, 2016 - $13 billion served through specialty distributors; $3 billion served by big boxes, lumberyards and other channels Specialty distribution remains highly fragmented - a few larger players and ~400 local & regional participants ($ in billions) ($ in billions) (1) Specialty Distributors Other Channels ~400 Smaller Competitors - ~47%Top 4 - ~53% Source: Management estimates and public filings. (1) Represents GMS, L&W Supply, Foundation Building Materials and Allied (Ceilings and Wallboard) revenue. 16 $13 $3 ~$6 ~$7 Specialty Distributors Market Share North American Market Large, fragmented market with top four specialty distributors representing only ~53% of the market (1)

Significant Opportunity to Drive Earnings Growth Operating leverage on branch cost structure - Distribution network has historically supported significantly higher volumes per branch - Leads to operating leverage on the fixed costs at the branches (Wallboard volume in million square feet) 30 14% 13% 12% 25 10% 20 Operating excellence initiatives - Pricing optimization, enhanced fleet utilization and working capital management to yield continued efficiencies 8% 15 6% 10 4% Favorable Pricing Environment - Consolidated gypsum and ceiling supplier bases - Increased demand and tighter capacity among distributors 5 2% 0 0% FY2006 FY2011 FY2017 Wallboard volume / branch Branch EBITDA margin Note: Fiscal year end April 30th. (1) Branch EBITDA margin calculated as Adj. EBITDA plus corporate expense divided by net sales. 17 24 9% 4% 17 11 Significant Branch Operating Leverage (1) Positioned to benefit from significant operating leverage and operational excellence initiatives to deliver enhanced profitability

Capitalizing on Large and Diverse End Markets Poised for Continued Growth (Billions square feet) (Seasonally Adj. starts in millions) 4.6% 1.4 1.3 3.6% 0.9 2015 2016 Long-Term Mean (1) 2015 2016 Long-Term Mean(1) 2015 2016 Long-Term Mean(2) (1) Since 1970. Private residential fixed investment as a percent of GDP since 1950. (2) 18 1.0 1.21.2 3.8% New Commercial Construction Residential R&R Activity Residential Housing Starts GMS’s business mix is diversified across commercial and residential as well as new construction and R&R end markets, all of which are expected to continue to see robust growth

Entrepreneurial Culture And Experienced Leadership Driving Superior Execution Senior management averages over 25 years in the industry and over 20 years with GMS VPs of Operations across all seven geographic divisions have 30+ years of industry experience and have worked with GMS for 25+ years on average Significantly enhanced Yard Support Center team with new leaders in finance, M&A, HR and legal Unique culture combining a results driven environment with a highly entrepreneurial, self starter attitude Attractive variable compensation structure, consisting of tiered, profit-based structure which incentivizes superior performance Delivering consistent, above market growth Unwavering focus on operational excellence drives enhanced margin expansion and earnings growth 19 Proven Track Record Entrepreneurial / Ownership Culture Significant Experience In The Industry

Financial Highlights Proven track record of driving consistent above market growth and share gains Above-Market Growth Ability to deliver superior service and a comprehensive product suite Well positioned to capitalize on growth in construction end markets Attractive End Market Dynamics Balanced exposure to residential, commercial and R&R end-markets providing tailwinds across the cycle Poised to benefit from significant operating leverage Continued margin improvement Ongoing focus on cost management and operational efficiency Attractive Cash Flow Dynamics Low capex requirements to fund growth 20 20 Well positioned to drive continued above-market growth

Q1 2018 Highlights Net sales increased 16.8% to a record $642.2 million Base business net sales up 7.8% Wallboard unit volume grew 11.8% to a record 914 million square feet Above-Market Growth Net income significantly increased 67.4% to $15.3 million, or EPS of $0.36 per share Gross profit increased 14.8% to $205.1 million Adjusted EBITDA grew 14.8% to $52.8 million Continued Profit Improvement In Q2 2018, acquired ASI Building Products, LLC, a leading provider of ceilings and other quality building products in Eastern Michigan Completed 8 acquisitions representing 18 branches since IPO (24 acquisitions representing 57 branches since FY2013) Accretive Acquisitions 2.9x leverage (net debt(1) / LTM PF Adjusted EBITDA(2)) as of July 31, 2017 Expanded First Lien Term Loan by $100 million, extended maturity to 2023, reduced the interest rate by 50 bps and used the net proceeds of $94 million to pay off the majority of the ABL Facility Attractive Capital Structure (1) Includes unamortized discount and deferred financing costs. Numbers may not add up due to rounding. (2) PF Adjusted EBITDA includes the earnings of acquired entities from the beginning of the periods presented to the date of such acquisitions, as well as certain purchasing synergies and cost savings, as defined in and permitted by the ABL Facility and the First Lien Facility, and which isY2016, FY2017 and FY18 Q1 LTM PF Adj. EBITDA includes approximately $12.1 million, $9.5 million and $3.6 million, respectively, from entities acquired in FY2016, FY2017 and FY18 Q1 LTM, respectively, for the period prior to their respective dates of acquisition used in the calculation of certain baskets to covenants in the Company’s debt agreements, including in connection with the Company’s ability to incur additional indebtedness. For a reconciliation of PF Adjusted EBITDA to net income, the most directly comparable GAAP metric, see Appendix. 21

Profitable Sales Expansion in Fiscal Q1 2018 Base Business (1) ($ in millions) Fiscal Q1 YOY Grow th Adj. EBITDA ($ mm) $60 (2) Per Day FY17 FY18 Actual $50 $40 $30 $20 $10 $0 WB Volume (MSF) WB Price ($ / MSF) 817 307 914 311 11.8% 1.3% 3.7% 2.1% $ $ Net Sales Wallboard Ceilings Steel Framing Other Products Total Net Sales $ 251.3 86.3 84.3 127.8 $ 284.7 99.7 104.7 153.1 13.3% 15.5% 24.1% 19.8% 4.9% 10.6% 10.0% 10.0% 3.3% 8.9% 8.3% 8.3% $ 549.8 $ 642.2 16.8% 7.8% 6.1% Fiscal Q1 2017 Fiscal Q1 2018 Shipping Days 63 64 Margin (3): 8.4% 8.2% 7.8% organic sales growth including +10% in ceilings, steel framing and other products Gross Profit ($ mm) 33.5% 33.0% 32.5% 32.0% 31.5% 31.0% 30.5% 30.0% 29.5% 29.0% $250 32.5% 31.9% Adjusted EBITDA grew 14.8% to $52.8 million reflecting stronger sales activity $200 $150 Adjusted EBITDA margins decreased 20 basis points, as expected, due to temporary gross margin pressure, which was partially offset by improved operating leverage $100 $50 $0 Fiscal Q1 2017 Fiscal Q1 2018 Gross Margin Gross Profit (1) When calculating our “base business” results, we exclude any branches that were acquired in the current fiscal year, prior fiscal year and three months prior to the start of the prior fiscal year. Base Business YOY growth adjusted for the difference in shipping days. For a reconciliation of Adj. EBITDA to Net Income (loss), the most directly comparable GAAP metric, see Appendix. (2) (3) 22 $205.1 $178.7 Commentary Fiscal Q1 2018 Gross Profit & Margin $52.8 $45.9 Fiscal Q1 2018 Performance Fiscal Q1 2018 Adjusted EBITDA (3)

Attractive Capital Structure Leverage of 2.9x Net Debt / LTM Pro Forma Adj. EBITDA as of 7/31/17, down from 3.4x Net Debt / LTM Pro Forma Adj. EBITDA as of 7/31/16 Substantial liquidity, with $20 million of cash and an additional $320 million undrawn on the ABL facility, as of 7/31/17 Moody’s and Standard & Poor’s current rating of B1/B+ (Moody’s upgraded GMS to B1 in July) In Q1 2018, expanded First Lien Term Loan by another $100 million, extended maturity to 2023, reduced the rate by 50 bps and used the net proceeds to pay down ABL facility ($ mm) 4/30/15 FYE 4/30/16 FYE 4/30/17 FYE 7/31/17 LTM 4.9x Cash and cash equivalents $12 $19 $15 $20 Asset-Based Revolver First Lien Term Loan Second Lien Term Loan Capital Lease and Other 17 386 160 10 102 382 160 14 103 478 - 14 13 576 - 13 4/30/15 4/30/16 4/30/17 LTM 7/31/17 (1) Includes unamortized discount and deferred financing costs. Numbers may not add up due to rounding. (2) PF Adjusted EBITDA includes the earnings of acquired entities from the beginning of the periods presented to the date of such acquisitions, as well as certain purchasing synergies and cost savings, as defined in and permitted by the ABL Facility and the First Lien Facility, and which is used in the calculation of certain baskets to covenants in the Company’s debt agreements, including in connection with the Company’s ability to incur additional indebtedness. FY2016, FY2017 and FY18 Q1 LTM PF Adj. EBITDA includes approximately $12.1 million, $9.5 million and $3.6 million, respectively, from entities acquired in FY2016, FY2017 and FY18 Q1 LTM, respectively, for the period prior to their respective dates of acquisition.. For a reconciliation of PF Adjusted EBITDA to net income, the most directly comparable GAAP metric, see Appendix. 23 PF Adj. EBITDA (1)$114$150$198$199 Total Debt / PF Adj. EBITDA5.0x4.4x3.0x3.0x Net Debt / PF Adj. EBITDA4.9x4.3x2.9x2.9x Total Debt$573$658$595603 4.3x 2.9x2.9x Net Debt / PF Adjusted EBITDA Leverage Summary Commentary

Summary Quarterly Financials Note: Fiscal year end April 30. 25 (In millions, except per share data) 1Q17 2Q17 3Q17 4Q17 (Unaudited) Wallboard Volume (MSF) 818 891 842 906 Wallboard Price ($ / '000 Sq. Ft.) $ 307 $ 303 $ 303 $ 311 Wallboard $ 251 $ 270 $ 255 $ 282 Ceilings 86 85 82 87 Steel framing 84 96 94 100 Other products 128 140 132 145 Net sales 550 592 563 615 Cost of sales 371 399 377 414 Gross profit 179 193 186 201 Gross margin 32.5% 32.6% 33.0% 32.7% Operating expenses: Selling, general and administrative expenses 135 150 147 153 Depreciation and amortization 16 17 18 18 Total operating expenses 151 167 166 171 Operating income (loss) 28 26 20 30 Other (expense) income: Interest expense (8) (7) (7) (7) Write-off of discount and deferred financing costs (5) (1) (0) - Other income, net 1 0 1 2 Total other (expense), net (12) (8) (7) (6) Income (loss) from continuing operations, before tax 15 18 14 25 Income tax expense (benefit) 6 1 5 10 Net income (loss) $ 9 $ 17 $ 8 $ 14 Weighted average shares outstanding: Basic 38,201 40,943 40,943 40,956 Diluted 38,602 41,320 41,578 41,759 Net income (loss) per share: Basic $ 0.24 $ 0.42 $ 0.20 $ 0.35 Diluted $ 0.24 $ 0.42 $ 0.20 $ 0.34 FY17 1Q18 914 $ 311 $ 285 100 105 153 642 437 205 31.9% 156 16 172 33 (8) (0) 0 (7) 25 10 15 40,971 42,172 $ 0.37 $ 0.36 3,458 $ 306 $ 1,058 341 374 546 2,319 1,561 759 32.7% 585 69 654 104 (29) (7) 4 (33) 72 23 $ 49 40,260 41,070 $ 1.21 $ 1.19

Quarterly Net Sales ($ in millions) (Unaudited) Base Business (1) (2) Acquisitions (2) Total Net Sales Business Days (3) Net Sales by Business Day Base Business Branches (4) (5) Acquired Branches (5) Total Branches Note: Fiscal year end April 30. (1) When calculating our “base business” results, we exclude any branches that were acquired in the current fiscal year, prior fiscal year and three months prior to the start of the prior fiscal year. (2) FY17 quarterly sales from acquisitions have been updated in accordance with our presentation of base business for the FY18 vs. FY17 comparative period. (3) Total business days for FY18 are 254. (4) Includes greenfields, which we consider extensions of “base business.” (5) FY17 acquired branches have been updated to reflect the number of acquired branches that are included within the sales from acquisitions 26 FY18 Business Days 1Q1864 days (+1) 2Q1865 days 3Q1862 days 4Q18 63 days FY18254 days (+1) 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 $ 544 $ 561 $ 511 $ 558 6 31 52 57 $ 2,173 146 $ 586 56 $ 550 $ 592 $ 563 $ 615 63 65 62 63 $ 8.7 $ 9.1 $ 9.1 $ 9.8 185 188 188 189 5 15 16 16 $ 2,319 253 $ 9.2 189 16 $ 642 64 $ 10.0 190 16 190 203 204 205 205 206

Quarterly Net Income to Adjusted EBITDA Commentary A. Represents non-cash compensation expenses related to stock appreciation rights agreements B. Represents non-cash compensation expense related to changes in the fair values of noncontrolling interests C. Represents non-cash equity-based compensation expense related to the issuance of stock options D. Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility E. Represents one-time costs related to our initial public offering and acquisitions (including the Acquisition) paid to third party advisors, including fees to financial advisors, accountants, attorneys and other professionals as well as costs related to the retirement of corporate stock appreciation rights. Also included are one-time bonuses paid to certain employees in connection with the Acquisition F. Represents management fees paid to AEA, which were discontinued after the IPO. 1Q17 includes fees paid for the month of May G. Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value H. Mark-to-market adjustments for certain financial instruments I. Represents costs paid to third party advisors related to the secondary public offerings of our common stock J. Represents costs paid to third party advisors related to debt refinancing activities. 27 Adjusted EBITDA Reconciliation ( $ in 000s) (Unaudited) Net Income (Loss) Add: Interest Expense Add: Write off of debt discount and deferred financing fees Less: Interest Income Add: Income Tax Expense Add: Depreciation Expense Add: Amortization Expense EBITDA Adjustments Stock appreciation rights expense (benefit) (A) Redeemable noncontrolling interests (B) Equity-based compensation (C) Severance and other permitted costs (D) Transaction costs (acquisition and other) (E) Loss (gain) on disposal of assets AEA management fee (F) Effects of fair value adjustments to inventory (G) Interest rate swap / cap mark-to-market (H) Secondary Public Offering (I) Debt Related Costs (J) Total Add-Backs Adjusted EBITDA 1Q17 2Q17 3Q17 4Q17 $ 9,163 $ 17,224 $ 8,227 $ 14,272 7,577 7,154 7,431 7,198 5,426 1,466 211 - (43) (35) (23) (51) 6,159 710 5,363 10,422 6,382 6,548 6,465 6,170 9,413 10,820 11,851 11,591 $ 44,077 $ 43,887 $ 39,525 $ 49,602 (92) (144) (498) 882 292 2,531 256 457 673 686 622 553 140 118 57 (472) 654 1,827 566 (798) (198) 68 (114) (94) 188 - - - 164 457 155 170 43 89 109 141 - - - 1,385 - - - 265 $ 1,864 $ 5,632 $ 1,153 $ 2,489 $ 45,941 $ 49,519 $ 40,678 $ 52,091 FY17 1Q18 $ 15,343 7,500 74 (23) 10,060 5,990 10,355 $ 49,299 590 866 473 205 159 (390) - - 196 631 723 $ 3,453 $ 52,752 $ 48,886 29,360 7,103 (152) 22,654 25,565 43,675 $ 177,091 148 3,536 2,534 (157) 2,249 (338) 188 946 382 1,385 265 $ 11,138 $ 188,229

LTM Net Income to Pro Forma Adjusted EBITDA Commentary ( $ in 000s) (Unaudited) 1Q18 LTM 2017 2016 2015 A. Represents non-cash compensation expenses related to stock appreciation rights agreements $ 12,564 $ (11,697) B. Net Income (Loss) $ 55,066 $ 48,886 Represents non-cash compensation expense related to changes in the fair values of noncontrolling interests Add: Interest Expense Add: Write off of debt discount and deferred financing fees Less: Interest Income Add: Income Tax Expense Add: Depreciation Expense Add: Amortization Expense 29,283 1,751 (132) 26,555 25,173 44,617 29,360 7,103 (152) 22,654 25,565 43,675 37,418 - (928) 12,584 26,667 37,548 36,396 - (1,010) (6,626) 32,208 31,957 C. Represents non-cash equity-based compensation expense related to the issuance of stock options D. Represents non-recurring expenses related specifically to the AEA acquisition of GMS $ 125,853 $ 81,228 E. EBITDA $ 182,313 $ 177,091 Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility Adjustments Stock appreciation rights expense (benefit) Redeemable noncontrolling interests Equity-based compensation AEA transaction related costs Severance and other permitted costs Transaction costs (acquisition and other) (Gain) on disposal of assets AEA management fee Effects of fair value adjustments to inventory Secondary Public Offering Interest rate swap / cap mark-to-market Debt Related Costs Total Add-Backs F. Represents one-time costs related to our initial public offering and acquisitions (including the Acquisition) paid to third party advisors, including fees to financial advisors, accountants, attorneys and other professionals as well as costs related to the retirement of corporate stock appreciation rights. Also included are one-time bonuses paid to certain employees in connection with the Acquisition 830 4,110 2,334 - (92) 1,754 (530) - 782 2,016 535 988 148 3,536 2,534 - (157) 2,249 (338) 188 946 1,385 382 265 1,988 880 2,699 - 379 3,751 (645) 2,250 1,009 2,268 1,859 6,455 837 413 1,891 1,089 2,250 5,012 (A) (B) (C) (D) (E) (F) (G) (H) (I) (J) (K) G. Represents management fees paid to AEA, which were discontinued after the IPO. 19 2,494 H. Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value $ 12,727 $ 11,138 $ 12,330 $ 24,568 I. Represents costs paid to third party advisors related to the secondary public offerings of our common stock Adjusted EBITDA $ 195,040 $ 188,229 $ 138,183 $ 105,796 Contributions from acquisitions Pro Forma Adjusted EBITDA 3,565 9,500 12,093 8,064 J. K. (L) Mark-to-market adjustments for certain financial instruments $ 198,605 $ 197,729 $ 150,276 $ 113,860 Represents costs paid to third party advisors related to debt refinancing activities. L. Pro forma impact of earnings from acquisitions from the beginning of the LTM period to the date of acquisition 28 Pro Forma Adjusted EBITDA Reconciliation

Net Income to Adjusted EBITDA Commentary ($ in 000s) (Unaudited) A. Represents compensation paid to certain executives who were majority owners prior to the AEA acquisition of GMS. Following the acquisition, these executives’ compensation agreements were amended and, going forward, GMS does not anticipate additional adjustments 2015 2014 (1) 2013 2012 $ (11,697) $(219,814) $(182,627) $ (7,830) Net income (loss) Income tax expense (benefit) Discountinued operations, net of tax Interest income Interest expense Change in fair value of mandatorily redeemable shares Depreciation expense Amortization expense (6,626) - (1,010) 36,396 - 32,208 31,957 (240) - (922) 7,180 200,004 16,042 2,556 11,534 - (798) 4,413 198,212 11,665 72 2,658 (362) (885) 2,966 8,952 7,840 732 B. Represents non-cash compensation expenses related to stock appreciation rights agreements C. Represents non-cash compensation expense related to changes in the fair values of noncontrolling interests D. Represents non-cash equity-based compensation expense related to the issuance of stock options E. Represents non-recurring expenses related specifically to the AEA acquisition of GMS $ 81,228 $ 4,806 $ 42,471 $ 14,071 EBITDA F. Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility Adjustments Executive compensation Stock appreciation rights expense (benefit) Redeemable noncontrolling interests Equity-based compensation AEA transaction related costs Severance costs and other permitted costs Transaction costs (acquisition and other) Loss (gain) on disposal of assets AEA management fee Effects of fair value adjustments to inventory Interest rate swap / cap mark-to-market Pension withdrawal Total Add-Backs $ - 2,268 1,859 6,455 837 413 1,891 1,089 2,250 5,012 2,494 - $ 2,447 1,368 3,028 28 67,964 - - (864) 188 8,289 (192) - $ 13,420 1,061 2,195 82 230 (30) - (2,231) - - 313 - $ 8,266 253 407 (154) 133 (205) - (556) - - - 10,179 (A) (B) (C) (D) (E) (F) (G) G. Represents one-time costs related to our initial public offering and acquisitions (including the Acquisition) paid to third party advisors, including fees to financial advisors, accountants, attorneys and other professionals as well as costs related to the retirement of corporate stock appreciation rights. Also included are one-time bonuses paid to certain employees in connection with the Acquisition H. Represents management fees paid to AEA, which were discontinued after the IPO. (H) (I) (J) (K) I. Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value 24,568 82,256 15,040 18,323 J. K. Mark-to-market adjustments for certain financial instruments Adjusted EBITDA $105,796 $ 87,062 $ 57,511 $ 32,394 Represents costs incurred in connection with withdrawal from a multi-employer pension plan (1) FY14 is comprised of 11 month period (predecessor) and one month period (successor) 29 Adjusted EBITDA Reconciliation

Quarterly Cash Flows ($ in millions) (Unaudited) Historical 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 Net income (loss) Non-cash changes Changes in primary working capital components: Trade accounts and notes receivable Inventories Accounts payable Cash provided by (used in) operating activities $ 9.2 (5.0) $ 17.2 11.5 $ 8.2 23.8 $ 14.3 30.1 $ 48.9 60.4 15.3 (2.8) (19.4) (17.1) 1.7 0.0 3.7 (1.1) 16.1 (12.3) (0.3) (17.2) 7.3 (4.1) (20.4) (18.4) (3.8) (12.9) (3.3) 9.5 (30.6) 31.3 35.6 30.4 66.7 5.9 Purchases of property and equipment Proceeds from sale of assets Purchase of financial instruments Acquisitions of businesses, net of cash acquired Cash (used in) provided by investing activities (2.6) 0.8 - (26.6) (2.4) 0.5 - (113.4) (1.9) 1.9 - (6.0) (4.2) 0.8 - (4.5) (11.1) 4.0 - (150.4) (5.5) 1.4 - (3.1) (28.3) (115.3) (6.0) (7.9) (157.5) (7.2) Cash provided by (used in) financing activities 49.7 90.5 (35.4) (18.5) 86.3 6.6 Increase (decrease) in cash and cash equivalents Balance, beginning of period Balance, end of period (9.2) 19.1 6.6 9.8 (5.8) 16.4 4.0 10.6 (4.5) 19.1 5.2 14.6 $ 9.8 $ 16.4 $ 10.6 $ 14.6 $ 14.6 19.8 Supplemental cash flow disclosures: Cash paid for income taxes Cash paid for interest $ $ 6.5 6.6 $ $ 24.3 6.6 $ $ 9.0 6.9 $ $ 9.3 6.4 $ $ 49.2 26.4 $ $ 1.8 6.8 30

SG&A Adjustments Table Commentary A. Represents non-cash compensation expenses related to stock appreciation rights agreements (Unaudited) ($ in millions) SG&A - Reported Adjustments Stock appreciation rights expense (benefit) Redeemable noncontrolling interests Equity-based compensation Severance and other permitted costs Transaction costs (acquisition and other) Loss (gain) on disposal of assets AEA management fee Secondary Public Offering Debt Related Costs SG&A - Adjusted 1Q17 2Q17 3Q17 4Q17 1Q18 $ 135.1 $ 149.8 $ 147.3 $ 153.0 $ 156.1 B. Represents non-cash compensation expense related to changes in the fair values of noncontrolling interests (A) (B) (C) (D) (E) 0.1 (0.3) (0.7) (0.1) (0.7) 0.2 (0.2) - - 0.1 (2.5) (0.7) (0.1) (1.8) (0.1) - - - 0.5 (0.3) (0.6) (0.1) (0.6) 0.1 - - - (0.9) (0.5) (0.6) 0.5 0.8 0.1 - (1.4) (0.3) (0.6) (0.9) (0.5) (0.2) (0.2) 0.4 - (0.6) (0.7) C. Represents non-cash equity-based compensation expense related to the issuance of stock options D. Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility (F) (G) (H) E. Represents one-time costs related to our initial public offering and acquisitions (including the Acquisition) paid to third party advisors, including fees to financial advisors, accountants, attorneys and other professionals as well as costs related to the retirement of corporate stock appreciation rights. Also included are one-time bonuses paid to certain employees in connection with the Acquisition $ 133.4 $ 144.7 $ 146.4 $ 150.8 $ 152.8 F. Represents management fees paid to AEA, which were discontinued after the IPO. 1Q17 includes fees paid for the month of May G. Represents costs paid to third party advisors related to the secondary public offerings of our common stock H. Represents costs paid to third party advisors related to debt refinancing activities. 31 FY2017 $ 585.1 (0.1) (3.5) (2.5) 0.2 (2.2) 0.3 (0.2) (1.4) (0.3) $ 575.3 GAAP SG&A Reconciliation