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Drywall for a 20x20 Garage

Sheets, type X and finishing materials for a 20 x 20 ft garage at 8, 9 and 10 ft walls, with a layout of every wall. Change the size, doors or what is above in the calculator.

  • 20 x 20 ft
  • 8, 9 and 10 ft walls
  • Type X split
  • Wall diagrams

By · Updated

Garage size

ft
Garage door wall
ft
Front to back
ft

Connection to the house

Walls shared with the house
What is above the garage?

Openings

On the front wall
Into the house
3 x 5 ft
Garage door size

Board

Sheet size

Your estimate

2024 IRC Table R302.6, model code minimum
21sheets in total
no type X required

1/2 in, required

Sheets124' x 12', offcuts reused
Ceiling20 ft wideAttic above: 1/2 in minimum on the garage side
Left wall20 ft wideShared with the house: 1/2 in minimum on the garage side

1/2 in, optional

Sheets94' x 12', offcuts reused
Front wall20 ft wideNot required by Table R302.6
Back wall20 ft wideNot required by Table R302.6
Right wall20 ft wideNot required by Table R302.6

Counts come from a sheet-by-sheet layout with offcuts reused within each product, plus no spare. Add one sheet per ten, and confirm local amendments with your building department.

12234456778920 ft
Ceiling, 1/2 in, required20 ft x 20 ft, horizontal, 12 pieces, 7 butt joints
Garage door122220 ft
Front wall, 1/2 in, optional20 ft x 8 ft, horizontal, 4 pieces, 1 butt joint
Door910111220 ft
Left wall, 1/2 in, required20 ft x 8 ft, horizontal, 4 pieces, 1 butt joint
3445620 ft
Back wall, 1/2 in, optional20 ft x 8 ft, horizontal, 5 pieces, 3 butt joints
678920 ft
Right wall, 1/2 in, optional20 ft x 8 ft, horizontal, 4 pieces, 2 butt joints

20 x 20 garage: sheets at each wall height

4x12 sheets, walls and ceiling, one 16 x 7 ft door
GarageWallsBoard areaAttic above: 1/2 inLiving above: type X + 1/2 in
20 x 20 ft8 ft907 sq ft21 sheets9 + 12 = 21
20 x 20 ft9 ft987 sq ft23 sheets9 + 14 = 23
20 x 20 ft10 ft1,067 sq ft24 sheets9 + 15 = 24

A 20 x 20 ft garage with 8 ft walls takes 21 sheets of 4x12 drywall for the walls and ceiling, laid out sheet by sheet with a 16 x 7 ft garage door and one entry door deducted. That is 507 sq ft of wall and 400 sq ft of ceiling. With 9 ft walls it is 23 sheets, and with 10 ft walls 24. If there is a room above, 9 of the sheets, the whole ceiling, must be 5/8 in type X.

Drywall for a 20 x 20 garage by wall height

  • 8 ft walls: 640 sq ft of gross wall, 21 sheets of 4x12 with only attic above, or 9 type X plus 12 of 1/2 in with living space above.
  • 9 ft walls: 720 sq ft of gross wall, 23 sheets with attic above, or 9 type X plus 14 of 1/2 in.
  • 10 ft walls: 800 sq ft of gross wall, 24 sheets with attic above, or 9 type X plus 15 of 1/2 in.

Twenty by twenty is the smallest common 2 car garage: two cars fit, with little room to open doors or walk around them. The counts assume the left wall is shared with the house and every surface is boarded; the calculator above lets you change both, and the door size.

Mud, tape and screws to finish it

For the 8 ft version, plan on about 141 lb of all-purpose joint compound, 373 ft of paper tape and 1,007 drywall screws, using the site's rules of 140 lb of compound and 370 ft of tape per 1,000 sq ft of board, and a screw allowance of 1 per sq ft on walls and 1.25 on ceilings. Use the mud and screw calculators for a closer count by finish level and framing.

Does it need type X?

Only the ceiling, and only when part of the house is above it, under 2024 IRC Table R302.6. The wall shared with the house needs at least 1/2 in gypsum board on the garage side, and so does a ceiling with only attic above.

This page explains the model International Residential Code. Your state, county or city may adopt a different edition or amend it, and some require 5/8 in type X on every garage surface. Check your local code with the building department before you buy board.

Frequently asked questions

21 sheets of 4x12 for the walls and ceiling with 8 ft walls, 23 with 9 ft walls and 24 with 10 ft walls, with a 16 x 7 ft garage door and an entry door deducted. Add one spare per ten sheets.

Primary references

Manufacturer and industry guidance used to check this article.

Product instructions, tested assemblies and local code take priority over general guidance.

Keep going

Related tools

How Many Sheets of Drywall for a 2 Car Garage?Table of drywall sheets for common 2 car garage sizes, wall heights and Type X cases.Garage Drywall Code RequirementsInteractive IRC R302.6 checker: 1/2 in vs 5/8 in Type X per garage surface.Drywall Mud CalculatorJoint compound by sheets or sq ft, finish level and product, plus sheets per bucket.Garage Drywall CalculatorGarage takeoff split into type X and regular board by the IRC separation table.