GMS Quarterly Review Fiscal Q4 2018

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 2019 and beyond. In addition, statements regarding potential acquisitions and future greenfield locations and statements regarding the impact of the recent tax legislation, fiscal 2018 and 2019 effective tax rates and the expected use of tax savings are forward-looking statements, as well as statements regarding the markets in which the Company or Titan operates, product expansion opportunities and the potential for growth in the commercial, residential and repair and remodeling, or R&R, markets. In addition, statements relating to the Titan acquisition, including the combination of best practices, statements regarding expected synergies, cost savings, margin improvement, expected accretion and its expected contribution to the Company’s Adjusted EBITDA for the eleven months ending April 30, 2019, are forward-looking statements. 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 and Canada; 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; the possibility that the expected synergies and cost savings and financial impacts from the Titan acquisition will not be realized, or will not be realized within the expected time period; the risk that the GMS and Titan businesses will not be integrated successfully; disruption from the transaction making it more difficult to maintain business and operational relationships and to accomplish other GMS objectives; the risk of customer attrition; and other factors described in the "Risk Factors" section in our Annual Report on Form 10-K for the fiscal year ended April 30, 2018, and in our other periodic reports filed with the SEC. In addition, the statements in this presentation are made as of June 28, 2018. 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 June 28, 2018. 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. Financial information related to Titan’s performance in periods prior to the acquisition included in this release were provided by Titan and are unaudited. 2

Fiscal Q4 and Fiscal 2018 Highlights 3 We achieved solid fourth quarter results, capping off a successful fiscal 2018 Net sales increased 3.4% to a record $635.8 million, base business net sales up 2.0% Wallboard price increased 2.4% Net income of $9.9 million, or EPS of $0.24 per diluted share Adjusted EBITDA declined 3.9% to $50.1 million Opened greenfield location in Hartford, CT on February 1, 2018 On April 2, 2018, acquired the GSD distribution operations of Grabber Construction Products, Inc. in Concord, CA and the GSD assets of CMH Distributing, Inc. in Kearney, NE Initiated a strategic cost reduction plan in May of this year to improve our operational efficiency We expect the actions that we have taken to generate annualized cost savings of approximately $20.0 million dollars Fiscal 2018 Highlights Closed June 1, 2018, establishing 30 location footprint in Canada and expanding the leading North American distributor of wallboard and ceilings with over 240 locations across 42 states and 5 provinces Pro forma LTM 4/30/18 net sales of ~$3 billion and Adjusted EBITDA of ~$302 million (1) Expected to be immediately accretive to Adjusted EPS and Adjusted EBITDA margin Strategic Cost Reduction Plan Titan Acquisition Update Fiscal Q4 2018 Highlights Sales increased 8.3% to a record $2.5 billion, base business net sales up 4.5% Net income of $63.0 million, or EPS of $1.49 per diluted share, grew $14.1 million or 28.8% Adjusted EBITDA increased 5.9% to a record $199.3 million Executed 5 acquisitions and opened 3 new greenfields For illustrative purpose only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation.

Titan Acquisition Creates Well-Balanced Platform Built for Growth in the United States and Canada Sales by Product (LTM) End Market Mix (LTM) Combined (2) Revenue (LTM) $2.5 billion $0.5 billion $3.0 billion Distribution Branches 214 30 244 Number of Employees 4,600 1,200 5,800 Based on financial information provided by Titan, calculated using 12/31/17 audited financial statements rolled forward for January through April 2018’s unaudited results. For illustrative purpose only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation. (US$ in millions) 4 (1) (LTM as of April 30, 2018) Wallboard ~44% Steel ~ 16% Ceilings ~ 15% Insulation ~ 4% Other ~20% Wallboard , 43% Steel , 15% Ceilings , 13% Insulation , 7% Other , 23% Residential ~40% Commercial ~60% Residential ~45% Commercial ~55% Residential 61% Commercial / Industrial 27% Two - Step Distribution 12% Wallboard 32% Steel 6% Ceilings , 3% Insulation 19% Other 40%

Fiscal 2018 Pro Forma Summary 5 ($ in millions, April FYE) Pro Forma Adjusted EBITDA (1) (3) Pro Forma Net Sales & Gross Margin (3) ($ in millions, April FYE) % Margin (1) 3.3% 5.0% 6.4% 6.7% 7.4% 8.1% 7.9% 10.1% +600bps, excl. $23mm lease impact FY2015, FY2016, FY2017 and FY2018 PF Adj. EBITDA includes approximately $8.1 million, $12.1 million, $9.5 million and $1.3 million, respectively, from entities acquired in FY2015, FY2016, FY2017 and FY2018 respectively, for the period prior to their respective dates of acquisition. However, Adj. EBITDA margin excludes the impact of the entities acquired for the period prior to their respective dates of acquisition. For a reconciliation of PF Adj. EBITDA to Net Income (loss), the most directly comparable GAAP measure, see Appendix page 15. Based on financial information provided by Titan, calculated using 12/31/17 audited financial statements rolled forward for January through April 2018’s unaudited results. For illustrative purpose only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation. +61% since May 2016 IPO $106 $138 $188 $199 $199 $8 $12 $10 $1 $103 $32 $57 $87 $114 $150 $198 $201 $302 FY-12 FY-13 FY-14 FY-15 FY-16 FY-17 FY-18 FY-18 PF $991 $1,162 $1,353 $1,570 $1,858 $2,319 $2,511 $2,989 FY-12 FY-13 FY-14 FY-15 FY-16 FY-17 FY-18 FY-18 PF $ in millions FY18 GMS Actual Lease Impact FY18 GMS PF Titan + Synergies (2) FY18 GMS Combined PF (3) Net Sales $2,511.5 $2,511.5 $478.4 $2,989.9 Adjusted EBITDA (1) $200.5 $23.0 $223.5 $78.4 $301.9 Adjusted EBITDA Margin (1) 7.9% 8.9% 10.1% Improvement vs. Actual +100bps +220bps

Fiscal Q4 2018 Performance Gross Profit ($ mm) Fiscal Q4 2018 Gross Profit & Margin Adj. EBITDA(2) ($ mm) Fiscal Q4 2018 Adjusted EBITDA (2) 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, the most directly comparable GAAP metric, see Appendix. Margin (2): 8.5% 7.9% 2.0% organic sales growth, led by steel framing (5.5%), ceilings (+5.1%) and other products (+4.6%) Gross margin declined 30 bps from prior year Adjusted EBITDA declined 3.9% to $50.1 million reflecting lower gross margin on low single digit sales growth Adjusted EBITDA margin declined 60 bps from prior year, impacted by the 30 basis point decrease in gross margin and 30 basis point increase in SG&A expense, driven primarily by higher logistics costs Commentary (3.9%) YOY Fiscal Q4 2018 Performance 6 $52.1 $50.1 - 10.0 20.0 30.0 40.0 50.0 Fiscal Q4 2017 Fiscal Q4 2018 ($ in millions) Fiscal Q4 YOY Base FY17 FY18 Growth Business (1) WB Volume (MSF) 906 878 (3.1%) (3.6%) WB Price ($ / MSF) 311 $ 319 $ 2.4% Net Sales Wallboard 282.2 $ 280.0 $ (0.8%) (1.4%) Ceilings 87.5 95.6 9.3% 5.1% Steel Framing 100.2 107.0 6.8% 5.5% Other Products 145.1 153.2 5.6% 4.6% Total Net Sales 615.0 $ 635.8 $ 3.4% 2.0%

Fiscal 2018 Performance Gross Profit ($ mm) Fiscal 2018 Gross Profit & Margin Adj. EBITDA(2) ($ mm) Fiscal 2018 Adjusted EBITDA (2) 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, the most directly comparable GAAP metric, see Appendix. Margin (2): 8.1% 7.9% 4.5% organic sales growth, led by ceilings (+9.0%), other products (+7.0%) and steel framing (+5.4%) Gross margin declined approximately 10 bps from prior year Adjusted EBITDA increased 5.9% to a record $199.3 million, driven by strong sales growth Adjusted EBITDA margin declined 20 bps from prior year, primarily the result of a slight decrease in gross margin and a slight increase in SG&A Commentary +5.9% YOY Fiscal 2018 Performance 7 $188.2 $199.3 - 50.0 100.0 150.0 200.0 Fiscal 2017 Fiscal 2018 ($ in millions) Fiscal YOY Base FY17 FY18 Growth Business (1) WB Volume (MSF) 3,457 3,548 2.6% (0.5%) WB Price ($ / MSF) 306 $ 313 $ 2.2% Net Sales Wallboard 1,058.4 $ 1,109.5 $ 4.8% 1.5% Ceilings 341.0 387.4 13.6% 9.0% Steel Framing 374.2 411.6 10.0% 5.4% Other Products 545.6 603.0 10.5% 7.0% Total Net Sales 2,319.1 2,511.5 8.3% 4.5%

Fiscal 2018 Results – Operating Expenses 8 Full Year SG&A & SG&A % of Sales FY2018 vs. FY2017 SG&A Bridge Organic Adjusted SG&A expenses increased ~3.6% in Q4 and ~4.7% in fiscal 2018, primarily the result of higher logistics costs Significant cost reductions implemented since May 2018 G&A headcount reductions effective 6/26/18 Other G&A (travel & entertainment, professional fees, etc.) Total annualized Additional cost reduction initiatives underway, while continuing to invest in opportunities to increase sales and expand margin Commentary Adjusted SG&A excludes 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, as well as Adjusted EBITDA add backs. For a reconciliation of Adjusted SG&A to Reported SG&A, see Appendix page 18. Adjusted SG&A PF includes the impact of the $20.0 million cost reduction plan. (2) 25.2% 25.2% 24.9% 25.0% 24.1% Organic SG&A ($ in millions) ($ in millions) (1) $585.1 $633.9 $541.7 $567.1 $547.1 $480 $500 $520 $540 $560 $580 $600 $620 $640 $660 FY2017 FY2018 GAAP SG&A Adjusted SG&A Adjusted SG&A PF FY18 Q4 FY18 Payroll & Payroll Related 1.5 $ 13.8 $ Equipment Leases - Logistics 0.8 4.5 Fuel - Logistics 1.1 2.6 All Other 1.5 4.5 Total Adjusted SG&A (1) 4.9 $ 25.4 $ EBITDA Add-Backs 1.3 2.3 SG&A - Acquisitions 2.5 21.1 Total GAAP SG&A 8.7 $ 48.8 $ $16.6 mm 3.4 mm $20.0 mm

Capital Structure Pre and Post Titan Transaction Pre Titan transaction capital structure as of 4/30/18: Leverage of 2.8x Net Debt / LTM Pro Forma Adj. EBITDA, down from 2.9x Net Debt / LTM Pro Forma Adj. EBITDA as of 4/30/17 Post Titan transaction capital structure as of 4/30/18: Pro Forma leverage of 4.1x Net Debt / LTM Pro Forma Adj. EBITDA Compares favorably to 6.0x Net Debt / LTM Pro Forma Adj. EBITDA as of 4/30/14 and 4.3x pre-IPO Moody’s and Standard & Poor’s maintained current rating of B1/BB- FY18 PF capital structure reflects the conversion of existing GMS equipment operating leases to capital leases effective May 1, 2018 and the expected increase to PP&E and debt accounts by ~$75 million. Commentary Leverage Summary Net Debt / PF Adjusted EBITDA FY18 PF capital structure reflects the conversion of existing GMS equipment operating leases to capital leases effective May 1, 2018 and the expected increase to PP&E and debt accounts by ~$75 million. FY18 PF Adjusted EBITDA reflects the favorable impact to Adjusted EBITDA of ~$23 million related to the conversion of existing equipment operating leases to capital leases and $78 million of PF Adjusted EBITDA, including synergies, from the Titan acquisition. For illustrative purposes only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation. 9 (3) (3) 4.3x 2.9x 2.8x 4.1x FY16 FY17 FY18 FY18 PF (US$ in millions) FY16 FY17 FY18 FY18 PF Cash and cash equivalents $19 $15 $36 $12 Asset-Based Revolver 102 103 - 143 Term Debt 542 478 573 998 Assumed Liability for Prior Ownership - - - 15 Capital Lease and Other (1) 14 14 23 99 Total Debt $658 $595 $596 $1,255 PF Adj. EBITDA (2) $150 $198 $201 $302 Total Debt / PF Adj. EBITDA 4.4x 3.0x 3.0x 4.2x Net Debt / PF Adj. EBITDA 4.3x 2.9x 2.8x 4.1x

Leading Specialty Distributor Poised for Continued Growth 10 Market Leader with Significant Scale Advantages – #1 North American Distributor of Wallboard and Ceilings Differentiated Service Model Drives Market Leadership Multiple Levers to Drive Market Leading Growth – Market Share, Greenfields, M&A, Operating Leverage Capitalizing on growth in Large, Diverse End Markets Entrepreneurial Culture with Dedicated Employees and Experienced Leadership Driving Superior Execution National Scale Combined With Local Expertise Market Leader with Scale Advantages

Appendix

Summary Quarterly Financials Note: Fiscal year end April 30. 12 (In millions, except per share data) 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 2Q18 3Q18 4Q18 FY18 (Unaudited) Wallboard Volume (MSF) 818 891 842 906 3,457 914 929 826 878 3,548 Wallboard Price ($ / '000 Sq. Ft.) 307 $ 303 $ 303 $ 311 $ 306 $ 311 $ 311 $ 312 $ 319 $ 313 $ Wallboard 251 $ 270 $ 255 $ 282 $ 1,058 $ 285 $ 288 $ 256 $ 280 $ 1,110 $ Ceilings 86 85 82 87 341 100 102 90 96 387 Steel framing 84 96 94 100 374 105 103 97 107 412 Other products 128 140 132 145 546 153 155 142 153 603 Net sales 550 592 563 615 2,319 642 648 586 636 2,511 Cost of sales 371 399 377 414 1,561 437 436 390 430 1,693 Gross profit 179 193 186 201 759 205 212 195 206 819 Gross margin 32.5% 32.6% 33.0% 32.7% 32.7% 31.9% 32.8% 33.4% 32.4% 32.6% Operating expenses: Selling, general and administrative expenses 135 150 147 153 585 156 160 156 162 634 Depreciation and amortization 16 17 18 18 69 16 17 16 16 66 Total operating expenses 151 167 166 171 654 172 177 173 178 699 Operating income 28 26 20 30 104 33 36 23 28 119 Other (expense) income: Interest expense (8) (7) (7) (7) (29) (8) (8) (8) (8) (31) Change in fair value of financial instruments (0) (0) (0) (0) (0) (0) (0) (0) (5) (6) Write-off of discount and deferred financing costs (5) (1) (0) - (7) (0) - - - (0) Other income, net 1 1 1 2 4 0 1 1 1 2 Total other expense, net (12) (8) (7) (6) (33) (7) (8) (7) (13) (35) Income from continuing operations, before tax 15 18 14 25 72 25 28 15 15 84 Income tax expense (benefit) 6 1 5 10 23 10 10 (4) 5 21 Net income 9 $ 17 $ 8 $ 14 $ 49 $ 15 $ 18 $ 20 $ 10 63 Weighted average shares outstanding: Basic 38,201 40,943 40,943 40,956 40,260 40,971 41,006 41,036 41,048 41,015 Diluted 38,602 41,320 41,578 41,759 41,070 42,128 42,146 42,228 42,151 42,163 Net income per share: Basic 0.24 $ 0.42 $ 0.20 $ 0.35 $ 1.21 $ 0.37 $ 0.44 $ 0.48 $ 0.24 $ 1.54 $ Diluted 0.24 $ 0.42 $ 0.20 $ 0.34 $ 1.19 $ 0.36 $ 0.43 $ 0.47 $ 0.24 $ 1.49 $

Quarterly Net Sales Note: Fiscal year end April 30. 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. FY17 quarterly sales from acquisitions have been updated in accordance with our presentation of base business for the FY18 vs. FY17 comparative period. Includes greenfields, which we consider extensions of “base business.” FY17 acquired branches have been updated to reflect the number of acquired branches that are included within the sales from acquisitions FY19 Business Days 1Q19 64 days 2Q19 65 days 3Q19 62 days 4Q19 63 days FY19 254 days 13 ($ in millions) 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 2Q18 3Q18 4Q18 FY18 (Unaudited) Base Business (1) (2) 544 $ 561 $ 511 $ 558 $ 2,173 $ 586 $ 590 $ 526 $ 569 $ 2,272 $ Acquisitions (2) 6 31 52 57 146 56 58 59 66 240 Total Net Sales 550 $ 592 $ 563 $ 615 $ 2,319 $ 642 $ 648 $ 586 $ 636 $ 2,512 $ Business Days 63 65 62 63 253 64 65 62 63 254 Net Sales by Business Day 8.7 $ 9.1 $ 9.1 $ 9.8 $ 9.2 $ 10.0 $ 10.0 $ 9.4 $ 10.1 $ 9.9 $ Base Business Branches (3) (4) 185 188 188 189 189 190 190 191 191 191 Acquired Branches (4) 5 15 16 16 16 16 20 21 23 23 Total Branches 190 203 204 205 205 206 210 212 214 214

Quarterly Net Income to Adjusted EBITDA Adjusted EBITDA Reconciliation Commentary Represents non-cash compensation expenses related to stock appreciation rights agreements 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 share-based awards Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility Represents one-time costs related to our initial public offering and acquisitions 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. Includes $1.186 million in other income recorded in the fourth quarter of fiscal 2017 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 Mark-to-market adjustments for certain financial instruments Represents costs paid to third party advisors related to the secondary public offerings of our common stock Represents costs paid to third party advisors related to debt refinancing activities 14 ( $ in 000s) 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 2Q18 3Q18 4Q18 FY18 (Unaudited) Net Income 9,163 $ 17,224 $ 8,227 $ 14,272 $ 48,886 $ 15,343 $ 18,023 $ 19,686 $ 9,919 $ 62,971 $ Add: Interest Expense 7,577 7,154 7,431 7,198 29,360 7,500 7,917 7,871 8,107 31,395 Add: Write off of debt discount and deferred financing fees 5,426 1,466 211 - 7,103 74 - - - 74 Less: Interest Income (43) (35) (23) (51) (152) (23) (26) (44) (84) (177) Add: Income Tax Expense (Benefit) 6,159 710 5,363 10,422 22,654 10,060 9,983 (4,488) 5,328 20,883 Add: Depreciation Expense 6,382 6,548 6,465 6,170 25,565 5,990 6,023 6,009 6,054 24,075 Add: Amortization Expense 9,413 10,820 11,851 11,591 43,675 10,355 10,690 10,481 9,928 41,455 EBITDA 44,077 $ 43,887 $ 39,525 $ 49,602 $ 177,091 $ 49,299 $ 52,610 $ 39,515 $ 39,252 $ 180,676 $ Adjustments Stock appreciation rights expense (income) (A) (92) (144) (498) 882 148 590 642 631 455 2,318 Redeemable noncontrolling interests (B) 292 2,531 256 457 3,536 866 164 340 498 1,868 Equity-based compensation (C) 673 686 622 553 2,534 473 375 429 418 1,695 Severance and other permitted costs (D) 140 118 57 (472) (157) 205 113 7 256 581 Transaction costs (acquisition and other) (E) ,(F) 654 1,827 305 (798) 1,988 159 88 75 3,049 3,370 Loss (gain) on disposal of assets (198) 68 (114) (94) (338) (390) (207) (51) 139 (509) AEA management fee (G) 188 - - - 188 - - - - - Effects of fair value adjustments to inventory (H) 164 457 155 170 946 - 187 89 48 324 Change in fair value of financial instruments (I) 43 89 109 141 382 196 238 276 5,415 6,125 Secondary public offerings (J) - - - 1,385 1,385 631 - 894 - 1,525 Debt transaction costs (K) - - 261 265 526 723 35 - 527 1,285 Total Add-Backs 1,864 $ 5,632 $ 1,153 $ 2,489 $ 11,138 $ 3,453 $ 1,635 $ 2,690 $ 10,805 $ 18,582 $ Adjusted EBITDA 45,941 $ 49,519 $ 40,678 $ 52,091 $ 188,229 $ 52,752 $ 54,245 $ 42,205 $ 50,057 $ 199,258 $

LTM Net Income to Pro Forma Adjusted EBITDA Pro Forma Adjusted EBITDA Reconciliation Commentary 15 Represents non-cash compensation expenses related to stock appreciation rights agreements 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 share-based awards Represents non-recurring expenses related specifically to the AEA acquisition of GMS Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility 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 Represents management fees paid to AEA, which were discontinued after the IPO Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value Mark-to-market adjustments for certain financial instruments Represents costs paid to third party advisors related to the secondary public offerings of our common stock Represents costs paid to third party advisors related to debt refinancing activities Pro forma impact of earnings from acquisitions from the beginning of the LTM period to the date of acquisition ( $ in 000s) 2018 2017 2016 2015 (Unaudited) Net Income (Loss) 62,971 $ 48,886 $ $ 12,564 $ (11,697) Add: Interest Expense 31,395 29,360 37,418 36,396 Add: Write off of debt discount and deferred financing fees 74 7,103 - - Less: Interest Income (177) (152) (928) (1,010) Add: Income Tax Expense 20,883 22,654 12,584 (6,626) Add: Depreciation Expense 24,075 25,565 26,667 32,208 Add: Amortization Expense 41,455 43,675 37,548 31,957 EBITDA 180,676 $ 177,091 $ $ 125,853 $ 81,228 Adjustments Stock appreciation rights expense (A) 2,318 148 1,988 2,268 Redeemable noncontrolling interests (B) 1,868 3,536 880 1,859 Equity-based compensation (C) 1,695 2,534 2,699 6,455 AEA transaction related costs (D) - - - 837 Severance and other permitted costs (E) 581 (157) 379 413 Transaction costs (acquisition and other) (F) 3,370 1,988 3,751 1,891 (Gain) loss on disposal of assets (509) (338) (645) 1,089 AEA management fee (G) - 188 2,250 2,250 Effects of fair value adjustments to inventory (H) 324 946 1,009 5,012 Change in fair value of financial instruments (I) 6,125 382 - - Secondary public offerings (J) 1,525 1,385 19 2,494 Debt transaction costs (K) 1,285 526 - - Total Add-Backs 18,582 $ 11,138 $ 12,330 $ 24,568 $ Adjusted EBITDA 199,258 $ 188,229 $ 138,183 $ 105,796 $ Contributions from acquisitions (L) 1,280 9,500 12,093 8,064 Pro Forma Adjusted EBITDA 200,538 $ 197,729 $ 150,276 $ 113,860 $

Net Income to Adjusted EBITDA Adjusted EBITDA Reconciliation Commentary 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 Represents non-cash compensation expenses related to stock appreciation rights agreements 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 Represents non-recurring expenses related specifically to the AEA acquisition of GMS Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility 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 Represents management fees paid to AEA, which were discontinued after the IPO Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value Mark-to-market adjustments for certain financial instruments Represents costs incurred in connection with withdrawal from a multi-employer pension plan 16 FY14 is comprised of 11 month period (predecessor) and one month period (successor) ($ in 000s) (Unaudited) 2015 2014 (1) 2013 2012 Net income (loss) $ (11,697) $(219,814) $(182,627) $ (7,830) Income tax expense (benefit) (6,626) (240) 11,534 2,658 Discountinued operations, net of tax - - - (362) Interest income (1,010) (922) (798) (885) Interest expense 36,396 7,180 4,413 2,966 Change in fair value of mandatorily redeemable shares - 200,004 198,212 8,952 Depreciation expense 32,208 16,042 11,665 7,840 Amortization expense 31,957 2,556 72 732 EBITDA $ 81,228 $ 4,806 $ 42,471 $ 14,071 Adjustments Executive compensation (A) $ - $ 2,447 $ 13,420 $ 8,266 Stock appreciation rights expense (benefit) (B) 2,268 1,368 1,061 253 Redeemable noncontrolling interests (C) 1,859 3,028 2,195 407 Equity-based compensation (D) 6,455 28 82 (154) AEA transaction related costs (E) 837 67,964 230 133 Severance costs and other permitted costs (F) 413 - (30) (205) Transaction costs (acquisition and other) (G) 1,891 - - - Loss (gain) on disposal of assets 1,089 (864) (2,231) (556) AEA management fee (H) 2,250 188 - - Effects of fair value adjustments to inventory (I) 5,012 8,289 - - Interest rate swap / cap mark-to-market (J) 2,494 (192) 313 - Pension withdrawal (K) - - - 10,179 Total Add-Backs 24,568 82,256 15,040 18,323 Adjusted EBITDA $105,796 $ 87,062 $ 57,511 $ 32,394

Quarterly Cash Flows 17 ($ in millions) (Unaudited) 1Q17 2Q17 3Q17 4Q17 FY17 1Q18 2Q18 3Q18 4Q18 FY18 Net income $ 9.2 $ 17.2 $ 8.2 $ 14.3 $ 48.9 15.3 $ 18.0 $ 19.7 $ 9.9 $ 63.0 Non-cash changes & other changes (5.0) 11.5 23.8 30.1 60.4 (2.8) 13.3 14.9 35.3 60.8 Changes in primary working capital components: Trade accounts and notes receivable (19.4) 0.0 16.1 (17.2) (20.4) (12.9) (8.9) 36.4 (26.3) (11.8) Inventories (17.1) 3.7 (12.3) 7.3 (18.4) (3.3) (4.0) (16.3) (11.2) (34.8) Accounts payable 1.7 (1.1) (0.3) (4.1) (3.8) 9.5 5.1 (20.3) 17.1 11.4 Cash provided by (used in) operating activities (30.6) 31.3 35.6 30.4 66.7 5.9 23.5 34.4 24.9 88.6 Purchases of property and equipment (2.6) (2.4) (1.9) (4.2) (11.1) (5.5) (2.9) (5.0) (10.3) (23.7) Proceeds from sale of assets 0.8 0.5 1.9 0.8 4.0 1.4 0.5 0.4 0.5 2.9 Acquisitions of businesses, net of cash acquired (26.6) (113.4) (6.0) (4.5) (150.4) (3.1) (15.3) (5.2) (4.8) (28.3) Cash (used in) provided by investing activities (28.3) (115.3) (6.0) (7.9) (157.5) (7.2) (17.7) (9.7) (14.6) (49.2) Cash provided by (used in) financing activities 49.7 90.5 (35.4) (18.5) 86.3 6.5 (5.8) (15.5) (2.8) (17.5) Increase (decrease) in cash and cash equivalents (9.2) 6.6 (5.8) 4.0 (4.5) 5.2 0.0 9.2 7.5 21.9 Balance, beginning of period 19.1 9.8 16.4 10.6 19.1 14.6 19.7 19.8 28.9 14.6 Balance, end of period $ 9.8 $ 16.4 $ 10.6 $ 14.6 $ 14.6 19.7 $ 19.8 28.9 $ 36.4 $ 36.4 Supplemental cash flow disclosures: Cash paid for income taxes $ 6.5 $ 24.3 $ 9.0 $ 9.3 $ 49.2 $ 1.8 $ 26.7 $ 6.6 $ 3.9 $ 39.0 Cash paid for interest $ 6.6 $ 6.6 $ 6.9 $ 6.4 $ 26.4 $ 6.8 $ 7.3 $ 7.1 $ 7.4 $ 28.6 Historical

Reconciliation of SG&A to Adjusted SG&A & Organic SG&A GAAP SG&A Reconciliation Commentary Represents non-cash compensation expenses related to stock appreciation rights agreements 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 Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility 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. Represents management fees paid to AEA, which were discontinued after the IPO. 1Q17 includes fees paid for the month of May Represents costs paid to third party advisors related to the secondary public offerings of our common stock Represents costs paid to third party advisors related to debt refinancing activities Represents SG&A incurred by 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 18 (Unaudited) 1Q17 2Q17 3Q17 4Q17 FY2017 1Q18 2Q18 3Q18 4Q18 FY2018 ($ in millions) SG&A - Reported 135.1 $ 149.8 $ 147.3 $ 153.0 $ 585.1 $ 156.1 $ 159.9 $ 156.3 $ 161.6 $ 633.9 $ Adjustments Stock appreciation rights expense (benefit) (A) 0.1 0.1 0.5 (0.9) (0.1) (0.6) (0.6) (0.6) (0.5) (2.3) Redeemable noncontrolling interests (B) (0.3) (2.5) (0.3) (0.5) (3.5) (0.9) (0.2) (0.3) (0.5) (1.9) Equity-based compensation (C) (0.7) (0.7) (0.6) (0.6) (2.5) (0.5) (0.4) (0.4) (0.4) (1.7) Severance and other permitted costs (D) (0.1) (0.1) (0.1) 0.5 0.2 (0.2) (0.1) (0.0) (0.3) (0.6) Transaction costs (acquisition and other) (E) (0.7) (1.8) (0.3) 0.8 (2.0) (0.2) (0.1) (0.1) (3.0) (3.4) Loss (gain) on disposal of assets 0.2 (0.1) 0.1 0.1 0.3 0.4 0.2 0.1 (0.1) 0.5 AEA management fee (F) (0.2) - - - (0.2) - - - - - Secondary Public Offering (G) - - - (1.4) (1.4) (0.6) - (0.9) - (1.5) Debt Related Costs (H) - - (0.3) (0.3) (0.5) (0.7) (0.0) - (0.5) (1.3) SG&A - Adjusted 133.4 $ 144.7 $ 146.4 $ 150.8 $ 575.3 $ 152.8 $ 158.7 $ 153.9 $ 156.3 $ 621.7 $ SG&A - Acquistions (I) 1.2 $ 6.1 $ 12.5 $ 13.8 $ 33.5 $ 12.1 $ 13.7 $ 14.5 $ 14.4 $ 54.6 $ Organic Adjusted SG&A 132.2 $ 138.6 $ 133.9 $ 137.0 $ 541.7 $ 140.7 $ 145.0 $ 139.5 $ 141.9 $ 567.1 $

LTM Net Income to Pro Forma Adjusted EBITDA Including WSB Titan Pro Forma Adjusted EBITDA Reconciliation Commentary 19 Note: Titan figures converted at CAD/USD average monthly exchange rate of 0.7816. For illustrative purpose only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation. Represents non-cash compensation expenses related to stock appreciation rights agreements 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 share-based awards Represents severance and other costs permitted in calculations under the ABL Facility and the First Lien Facility 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 Non-cash cost of sales impact of purchase accounting adjustments to increase inventory to its estimated fair value Mark-to-market adjustments for certain financial instruments Represents costs paid to third party advisors related to the secondary public offerings of our common stock Represents costs paid to third party advisors related to debt refinancing activities Pro forma impact of earnings from acquisitions from the beginning of the LTM period to the date of acquisition Represents the favorable impact to Adjusted EBITDA related to the conversion of existing GMS equipment operating leases to capital leases Represents Titan’s Adjusted EBITDA for the LTM 4/30/18 period. Based on 12/31/17 audited financial statements rolled forward April 2018’s unaudited results Represents the projected run-rate annual pre-tax procurement synergies associated with the combined company’s enhanced scale ( $ in 000s) LTM April 30, 2018 (Unaudited) Net Income (Loss) 62,971 $ Add: Interest Expense 31,395 Add: Write off of debt discount and deferred financing fees 74 Less: Interest Income (177) Add: Income Tax Expense 20,883 Add: Depreciation Expense 24,076 Add: Amortization Expense 41,454 EBITDA 180,676 $ Adjustments Stock appreciation rights expense (A) 2,318 Redeemable noncontrolling interests (B) 1,868 Equity-based compensation (C) 1,695 Severance and other permitted costs (D) 581 Transaction costs (acquisition and other) (E) 3,370 (Gain) loss on disposal of assets (509) Effects of fair value adjustments to inventory (F) 324 Change in fair value of financial instruments (G) 6,125 Secondary public offerings (H) 1,525 Debt transaction costs (I) 1,285 Total Add-Backs 18,582 $ Adjusted EBITDA 199,258 $ Contributions from acquisitions (J) 1,280 GMS Pro Forma Adjusted EBITDA (as reported) 200,538 $ Conversion of GMS operating leases (K) 23,000 Titan Adjusted EBITDA (L) 68,400 Cost Synergies (M) 10,000 Combined Pro Forma Adjusted EBITDA (1) 301,938 $

20 Assuming the effects of tax reform and the acquisition of Titan were effective 5/1/2017, the table below reflects the estimated impact of both on Adjusted Net Income: Commentary As reported in GMS's June 28, 2018 earnings release statement and WSB Titan 12/31/17 audited results adjusted for January through April 2018 unaudited results. Titan EBITDA Add-Backs are related to agreements Titan has with former shareholders based on the achievement of certain performance measures as well as transaction-related costs. Represents the projected run-rate annual pre-tax procurement synergies associated with the combined company’s enhanced scale. Estimated pro forma interest expense. As reported in GMS's June 28, 2018 earnings release statement. Calculated assuming all equipment was acquired under capital leases or purchased as opposed to operating leases and were, accordingly, 100% year-one tax deductible. Normalized cash tax rate based on the Tax Cuts and Jobs Act of 2017. Includes $35 million of rollover equity from Titan management, assuming a $31.00 share price of GMS common stock. Based on financial information provided by Titan, calculated using 12/31/17 audited financial statements rolled forward for January through April 2018’s unaudited results. For illustrative purpose only. Not prepared in accordance with Regulation S-X pro forma requirements. Actual results may vary. See “Forward-Looking Statement Safe Harbor” on page 2 of this presentation. FY 2018 Pro Forma Adjusted EPS Reconciliation +22.6% ($ in millions, except share and per share data) (Unaudited) FY 2018 Reported (1) GMS Tax Adjustments (6) FY 2018 GMS PF Titan Acquisition (9) FY 2018 Combined GMS PF (10) Pre-Tax Income (Loss) (1) $83.854 $83.854 ($18.105) $65.749 EBITDA Add-backs (2) 18.582 18.582 23.658 42.240 Write-off of discount and deferred financing fees 0.074 0.074 0.074 Cost synergies (3) 10.000 10.000 Estimated Pro-forma Interest (4) (26.267) (26.267) Purchase Acct-Depr & Amort - Legacy 17.000 17.000 Purchase Acct-Depr & Amort - GMS 21.271 21.271 30.000 51.271 Adjusted Pre-Tax Income (5) 123.781 - 123.781 36.286 160.067 Adjusted Income Tax Expense (6) 39.077 (14.224) 24.853 10.660 35.513 Adjusted Net Income $84.704 14.224 $ $98.928 $25.626 $124.554 Effective Tax Rate - Pro-forma (7) 31.6% 20.1% 22.2% Weighted average shares outstanding-Diluted (8) 42,163 42,163 1,129 43,292 Adjusted Net income per share-Diluted $2.01 0.34 $ $2.35 $0.53 $2.88 Accretion vs. FY 2018 GMS PF

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