GMS Quarterly Review Fiscal Q2 2017

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 the Company’s management that, although believed by the Company to be reasonable, are inherently uncertain. Forward-looking statements involve risks and uncertainties, including, but not limited to, economic, competitive, governmental and technological factors outside of its control, that may cause its 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, supply, and/or demand for products which GMS distributes; 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 the Company’s Annual Report on Form 10-K for the fiscal year ended April 30, 2016, and in its other periodic reports filed with the SEC. In addition, the statements in this presentation are made as of December 13, 2016. The Company undertakes 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 the Company’s views as of any date subsequent to December 13, 2016. Use of Non-GAAP and Adjusted Financial Information - To supplement GAAP financial information, the Company uses 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 the Company believes their exclusion can enhance an overall understanding of its past financial performance and also its prospects for the future. These adjustments to the Company’s GAAP results are made with the intent of providing both management and investors a more complete understanding of its operating performance by excluding non-recurring, infrequent or other non-cash charges that are not believed to be material to the ongoing performance of its 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

Q2 2017 Highlights Net sales increased 29.2% to $591.8 million Base business net sales up 10.8% Wallboard unit volume grew 27.2% to 891 million square feet Above-Market Growth Net income significantly increased to $17.2 million Gross margin expanded 120 basis points to 32.6% Adjusted EBITDA grew 42.3% to $49.5 million Continued Margin Improvement Completed four acquisitions, adding 10 branches across 4 states with combined LTM net sales of $156.7 million Acquisitions closed since February 1, 2015 represented 65.2% of Q2 2017 net sales growth Accretive Acquisitions Corporate debt upgraded to B2/B+ from B3/B by Moody’s and Standard & Poor's Closed on the refinancing of our existing $481 million term loan Expanded ABL Credit Agreement to $345 million from $300 million in Q3 2017 Average cash interest rate of ~3.9% based on October 31st leverage Attractive Capital Structure 3

Attractive Acquirer with Significant Consolidation Opportunity Quarter Rationale Acquisition Industry Structure: Large, highly fragmented industry comprised of ~400 competitors Similar business operations enable efficient integration Limited number of scaled players LTM Sales of $27.0 million Nice geographic fit with recent Michigan acquisition Founded in 1965 and headquartered in Southfield, MI, RBM is a preferred supplier of wallboard and other specialty products to the Eastern Michigan marketplace FY17 Q2 October 31, 2016 3 Branches LTM Sales of $30.0 million Strategic entrance into South Central Ohio Founded in 1996, UBM is a preferred supplier of wallboard and related construction products to the FY17 Q2 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 October 3, 2016 South Central Ohio marketplace. 3 Branches LTM Sales of $52.9 million Strategic entrance into South Florida Founded in 2008, OBS is a leading supplier of wallboard and related construction products to the South Florida marketplace. FY17 Q2 September 1, 2016 3 Branches LTM Sales of $46.8 million Strategic entrance into the greater Philadelphia metropolitan area Over its 20+ year operating history, SKBM has built an extremely strong reputation for customer service in the market. FY17 Q2 August 29, 2016 1 Branch Pipeline: The majority of the market is comprised of local, independent competitors representing significant opportunity LTM Sales of $26.7 million July 5, 2016 3 Branches FY17 Q1 LTM Sales of $8.5 million FY17 Q1 Maintain active dialogue with many potential targets at May 2, 2016 1 Branch any given time 4 Fiscal 2017 GMS Acquisitions Acquisition Strategy Employee-centric culture and industry track record positions GMS to drive additional growth through acquisitions

Continue to Use Multiple Levers to Drive Growth $184 Continued market share gains Greenfield branch openings Strategic acquisition opportunities in highly fragmented market FY-12 FY-13 FY-14 FY-15 FY-16 LTM Q2 17 End market recovery and expansion 14.4% 13.1% 9.9% Operating leverage Operational excellence 8.8% 8.6% CY-10 CY-11 CY-12 CY-13 CY-14 (2) CY-15 (3) LTM CY Q3 16 (4) (1) FY 2015, FY 2016 and FY17 Q2 LTM Pro Forma Adj. EBITDA includes approximately $8.1 million, $12.1 million and $19.1 million, respectively, from entities acquired in FY 2015, FY 2016 and FY17 Q2 LTM 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. (2) (3) (4) Includes the wallboard volume from entities acquired in FY 2015 assuming they were acquired on January 1, 2014. Includes the wallboard volume from entities acquired in FY 2016 assuming that the entities were acquired on January 1, 2015. Includes the wallboard volume from entities acquired in FY 2016 and FY 2017 assuming that the entities were acquired on October 1, 2015. 5 Margin Expansion 11.1% (5) 9.4% GMS Wallboard Market Share ’10–’16 Q3 LTM share gain: ~580 bps Market Growth % Margin (1) 3.3%5.0%6.4%6.7%7.4%7.9% Strategic Acquisitions CAGR: 50%$150 $19 $165 $114 $12 $138 $87 $8 $106 $58 $32 (1) Organic Growth Adjusted EBITDA (1) Strong track record of executing profitable growth strategy

Profitable Sales Expansion in Fiscal Q2 2017 ($ in millions) Fiscal Q2 YOY Grow th Base Business Adj. EBITDA ($ mm) (1) FY16 FY17 $50 Wallboard Volume (MSF) Wallboard Price ($/'000 Sq. Ft.) 700 306 891 303 27.2% (1.0%) 9.5% $40 $ $ $30 Net Sales ) $20 Wallboard Ceilings Steel Framing Other Products Total Net Sales $ 214.3 74.6 70.3 98.9 $ 270.0 85.4 96.1 140.4 26.0% 14.5% 36.7% 42.0% 8.6% 6.6% 16.1% 15.0% $10 $0 $ 458.1 $ 591.8 29.2% 10.8% Fiscal Q2 2016 Fiscal Q2 2017 Margin (2): 7.6% 8.4% Gross margin increased 120 basis points, primarily driven by increased product margins and, to a lesser extent, product mix Gross Profit ($ mm) $250 32.6% 33.0% 31.4% $200 32.0% Adjusted EBITDA grew 42.3% to $49.5 million reflecting stronger sales activity and higher gross margin $150 31.0% $100 30.0% Adjusted EBITDA margin improved ~80 basis points to 8.4% as a percentage of net sales reflecting better product margins $50 29.0% $0 28.0% Fiscal Q2 2016 Fiscal Q2 2017 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. For a reconciliation of Adj. EBITDA to Net Income (loss), the most directly comparable GAAP metric, see Appendix. 6 (2) $193.2 $143.9 Commentary Fiscal Q2 2017 Gross Profit & Margin $49.5 (5 $34.8 Fiscal Q2 2017 Performance Fiscal Q2 2017 Adjusted EBITDA (2) Tailored investments in Yard Support Center, IT and branch talent to support growth are paying off

One-Stop-Shop Outsized Impact on Other Products Sales Net Sales ($ mm) 150.0 $140.4 100.0 Steel Framing Fasteners 50.0 Joint Compound Wallboard - Fiscal Q2 2016 Fiscal Q2 2017 Acquisitions Base Business 15.0% organic growth in net sales of Other Products, well in excess of 10.8% overall organic growth Significant outperformance was driven by: Strategic initiatives focused on categories such as insulation, safety equipment and other specialty products Expanded 3rd party sales from Tool Source Warehouse, the company’s national distribution operation for tools and safety products Ceilings Tools Safety Products Insulation Continued price optimization Showroom expansions and resets Represents complementary product (other products) 7 Other Products Sales Growth Commentary $98.9 $34.0 $106.4 $6.4 $92.5 Fiscal Q2 2017 Other Products Net Sales “One-Stop-Shop” for the Interior Contractor GMS sells a complementary and complete product offering to the interior contractor who installs wallboard, ceilings and steel framing, and supplies all ancillary products needed to complete the job

Strong Gross Margin Profile Continued focus on growing profitability through market leadership, purchasing opportunities and price optimization $2,089 $1,162 $991 GMS gross margin growth largely independent of wallboard price GMS gross margin contribution diversified across product and end markets 2012 2013 2014 Net Sales 2015 2016 22001177 LQT2M LTM Gross Margin $309 $306 $305 Distribution gross margin profile more stable compared to building product manufacturers, helping to drive higher gross profit and operating leverage on rising sales $289 Expect gross margin to remain relatively stable through FY 2017 2012 2013 2014 2015 2016 Gross Margin 220017 QLT2M LTM Wallboard Price/MSF 8 30.5% 31.9% 32.6% $253 29.7% $219 29.0% 29.0% Wallboard Price vs Gross Margin $1,858 32.6% $1,570 31.9% $1,353 30.5% 29.7% 29.0% 29.0% Net Sales vs Gross Margin Gross Margin Profile

Attractive Capital Structure Leverage of 3.4x Net Debt / LTM Adj. EBITDA as of 10/31/16, continued improvement in credit metrics from 6.0x Net Debt / LTM Adj. EBITDA as of 4/30/14 and 4.3x as of 4/30/16 Substantial liquidity, with $16.4 million of cash on hand and an additional $168 million undrawn on the ABL Facility Moody’s and Standard & Poor’s upgraded GMS corporate debt in August to B2/B+ from B3/B based on increased construction activity and improved credit metrics Increased First Lien Term Loan, maturing 2021, by $100 million, reduced the rate by 25bps and used the net proceeds to pay down ABL Facility In Q3 2017, expanded ABL Credit Agreement to $345 million, reduced rate by 25bps, extended maturity to 2021 Average cash interest rate of ~3.9% based on October 31st leverage ($ mm) 4/30/14 FYE 4/30/15 FYE 4/30/16 FYE 10/31/16 LTM 6.0x Cash $33 $12 $19 $16 Asset-Based Revolver First Lien Term Loan Second Lien Term Loan Capital Lease and Other - 390 160 2 17 386 160 10 102 382 160 14 152 480 - 16 Total Debt PF Adj. EBITDA (1) Total Debt / PF Adj. EBITDA Net Debt / PF Adj. EBITDA $552 $87 6.3x 6.0x $573 $114 5.0x 4.9x $658 $150 4.4x 4.3x $648 $184 3.5x 3.4x 4/30/14 4/30/15 4/30/16 LTM 10/31/16 (1) 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. PF Adjusted EBITDA for the LTM period ended 10/31/16, fiscal year ended 4/30/16 and fiscal year ended 4/30/15 include PF adjustments of $19.1 million, $12.1 million and $8.1 million, respectively. For a reconciliation of Adjusted EBITDA to net income, the most directly comparable GAAP metric, see Appendix. 9 4.9x 4.3x 3.4x Net Debt / Adjusted EBITDA Leverage Summary Commentary

Leading Specialty Distributor Poised for Continued Growth 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 10

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Summary Quarterly Financials Note: Fiscal year end April 30. 12 (In millions, except per share data)1Q162Q163Q164Q16 (Unaudited) Wallboard Volume (MSF)681700646816 Wallboard Price ($ / '000 Sq. Ft.)$310$306$305$305 Wallboard$211$214$197$249 Ceilings79756578 Steel framing67706678 Other products959992122 Net sales452458420527 Cost of sales312314286353 Gross profit141144134174 Gross margin31.1%31.4%31.9%33.0% Operating expenses: Selling, general and administrative expenses110114112133 Depreciation and amortization16151617 Total operating expenses126130128150 Operating income (loss)1514624 Other (expense) income: Interest expense(9)(9)(9)(9) Change in fair value of financial instruments ---(0) Write-off of discount and deferred financing costs --- - Other income, net 1 0 1 2 Total other (expense), net(9)(9)(9) (7) Income (loss) from continuing operations, before tax 6 5(3)17 Income tax expense (benefit)33(1)8 Net income (loss)$3$3$(2)$9 Weighted average shares outstanding: Basic32,67732,73832,89132,893 Diluted32,83132,89832,89133,155 Net income (loss) per share: Basic$ 0.09$ 0.09$ (0.07)$ 0.27 Diluted$ 0.09$ 0.09$ (0.07)$ 0.27 FY16 1Q172Q17 818891 $307$303 $251$270 8685 8496 128140 550592 371399 179193 32.5%32.6% 135150 1617 151167 2826 (8)(7) (0) - (5)(1) 10 (12)(8) 1518 61 $9$17 38,20140,943 38,60241,320 $0.24$0.42 $0.24$0.42 2,843 $306 $871 297 281 409 1,858 1,265 593 31.9% 470 64 534 59 (37) (0) - 4 (34) 25 13 $13 32,799 33,125 $ 0.38 $ 0.38

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) FY16 quarterly sales from acquisitions have been updated in accordance with our presentation of base business for the FY17 vs. FY16 comparative period. (3) Quarterly business days for FY17 are 63, 65, 63 and 63 for 1Q17, 2Q17, 3Q17 and 4Q17, respectively. (4) Includes greenfields, which we consider extensions of “base business.” (5) FY16 acquired branches have been updated to reflect the number of acquired branches that are included within the sales from acquisitions 13 1Q16 2Q16 3Q16 4Q16 FY16 1Q17 2Q17 $ 428 $ 432 $ 379 $ 451 25 26 41 76 $ 1,642 216 $ 467 $ 479 83 113 $ 452 $ 458 $ 420 $ 527 64 64 61 65 $ 7.1 $ 7.2 $ 6.9 $ 8.1 149 151 152 153 7 8 26 33 $ 1,858 254 $ 7.3 153 33 $ 550 $ 592 63 65 $ 8.7 $ 9.1 153 156 37 47 156 159 178 186 186 190 203

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 Represents severance and other costs permitted in calculations under the ABL Facility and the Term Loan Facilities D. E. Represents one-time costs related to the IPO and acquisitions paid to third party advisors Represents management fees paid to AEA, which were discontinued after the IPO. 1Q17 includes fees paid for the month of May Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value F. G. H. Mark-to-market adjustments for certain financial instruments 14 Adjusted EBITDA Reconciliation ( $ in 000s) (Unaudited) Net Income (Loss) Add: Income Tax Expense Less: Interest Income Add: Interest 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) Total Add-Backs Adjusted EBITDA 1Q16 2Q16 3Q16 4Q16 $ 3,011 $ 2,825 $ (2,212) $ 8,940 2,8552,623(819)7,925 (230)(208)(247) (243) 9,2579,2609,4739,428 7,2736,4656,4696,460 8,7928,7979,54010,419 $ 30,958 $ 29,762 $ 22,204 $ 42,929 594692337365 554451167(292) 498863728610 55782452(1,054) 4151,3401,057 939 (25)305(205)(720) 562563562563 --786223 ---19 $ 3,155 $ 5,038 $ 3,484 $ 653 $ 34,113 $ 34,800 $ 25,688 $ 43,582 FY16 1Q17 2Q17 $ 12,564 12,584 (928) 37,418 26,667 37,548 $ 9,163 $ 17,224 6,159710 (43) (35) 13,0038,620 6,3826,548 9,41310,820 $ 44,077 $ 43,887 (92)(144) 2922,531 673686 140118 6541,827 (198)68 188-164457 4389 $ 1,864 $ 5,632 $ 45,941 $ 49,519 $ 125,853 1,988 880 2,699 379 3,751 (645) 2,250 1,009 19 $ 12,330 $ 138,183

LTM Net Income to Pro Forma Adjusted EBITDA Commentary ( $ in 000s) (Unaudited) 2Q17 LTM 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 Represents non-cash equity-based compensation expense related to the issuance of stock options Net Income (Loss) $ 33,115 Add: Income Tax Expense Less: Interest Income Add: Interest Expense Add: Depreciation Expense Add: Amortization Expense 13,975 (568) 40,524 25,859 40,192 C. D. Represents severance and other costs permitted in calculations under the ABL Facility and the Term Loan Facilities EBITDA $ 153,097 E. Represents one-time costs related to the IPO and acquisitions paid to third party advisors 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 Effects of fair value adjustments to inventory Interest rate swap / cap mark-to-market Total Add-Backs F. Represents management fees paid to AEA, which were discontinued after the IPO 466 2,698 2,697 (744) 4,477 (1,055) 1,313 1,630 151 (A) (B) (C) (D) (E) G. Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value H. I. Mark-to-market adjustments for certain financial instruments Pro forma impact of earnings from acquisitions from the beginning of the LTM period to the date of acquisition (F) (G) (H) $ 11,633 Adjusted EBITDA $ 164,730 19,149 Contributions from acquisitions Pro-forma Adjusted EBITDA (I) $ 183,879 15 Pro Forma Adjusted EBITDA Reconciliation

Quarterly Cash Flows ($ in millions) (Unaudited) Historical 1Q16 2Q16 3Q16 4Q16 FY16 1Q17 2Q17 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 $ 3.0 (2.6) $ 2.8 17.2 $ (2.2) 12.2 $ 8.9 35.4 $ 12.6 62.2 $ 9.2 (5.0) $ 17.2 11.5 (21.8) 0.4 2.7 (2.1) (0.6) (1.2) 25.8 (0.0) (15.6) (29.2) (0.4) 15.2 (27.3) (0.7) 1.1 (19.4) (17.1) 1.7 0.0 3.7 (1.1) (18.4) 16.1 20.2 29.8 47.7 (30.6) 31.3 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 (1.5) 0.4 - - (1.2) 5.7 - (0.9) (1.3) 0.7 - (82.9) (3.7) 3.1 - (29.9) (7.7) 9.8 - (113.6) (2.6) 0.8 - (23.3) (2.4) 0.5 - (112.3) (1.0) 3.6 (83.5) (30.5) (111.4) (25.0) (114.3) Cash provided by (used in) financing activities 20.3 (23.5) 61.3 12.4 70.5 46.4 89.5 Increase (decrease) in cash and cash equivalents Balance, beginning of period Balance, end of period 0.9 12.3 (3.8) 13.2 (2.0) 9.4 11.7 7.4 6.8 12.3 (9.2) 19.1 6.6 9.8 $ 13.2 $ 9.4 $ 7.4 $ 19.1 $ 19.1 $ 9.8 $ 16.4 Supplemental cash flow disclosures: Cash paid for income taxes $ $ 4.5 7.9 $ $ 9.7 8.6 $ $ 8.0 8.3 $ $ 3.9 9.8 $ $ 26.1 34.6 $ $ 6.5 6.6 $ $ 24.3 6.6 Cash paid for interest 16

SG&A Adjustments Table Commentary (Unaudited) ($ in millions) A. Represents non-cash compensation expenses related to stock appreciation rights agreements 1Q16 2Q16 3Q16 4Q16 1Q17 2Q17 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 SG&A - Adjusted $ 110.2 $ 114.4 $ 112.2 $ 133.2 $ 135.1 $ 149.8 B. Represents non-cash compensation expense related to changes in the fair values of noncontrolling interests (A) (B) (C) (D) (E) (0.6) (0.6) (0.5) (0.6) (0.4) 0.0 (0.6) (0.7) (0.5) (0.9) (0.8) (1.3) (0.3) (0.6) (0.3) (0.2) (0.7) (0.1) (1.1) 0.2 (0.6) (0.4) 0.3 (0.6) (0.1) (0.9) 0.7 (0.6) 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) - C. Represents non-cash equity-based compensation expense related to the issuance of stock options Represents severance and other costs permitted in calculations under the ABL Facility and the Term Loan Facilities D. (F) $ 107.1 $ 109.3 $ 109.5 $ 131.6 $ 133.4 $ 144.7 E. Represents one-time costs related to the IPO and acquisitions paid to third party advisors Represents management fees paid to AEA, which were discontinued after the IPO. 1Q17 includes fees paid for the month of May F. 17 FY2016 $ 470.0 (2.0) (0.9) (2.7) (1.6) (3.8) 0.6 (2.2) $ 457.6 GAAP SG&A Reconciliation

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