Inam Ur Rehman

How each kind of rule is checked

Different numbers come from different kinds of documents. This is where each kind comes from, and what happens when no document gives a number.

• Board sizes and weights

  Manufacturer submittals and data sheets

  Panel weights come from USG's published figures: 1.6 lb per sq ft for regular 1/2 in board, 1.25 for lightweight 1/2 in and 2.2 for 5/8 in type X. Widths, lengths and special sizes such as 54 in board come from the product submittals, not from what a store happens to stock.

• Installation and fastening

  USG's installation guide, GA-216 and IRC Table R702.3.5

  Screw spacing of 12 in on ceilings, 16 in on walls framed 16 in on center and 12 in on walls framed 24 in on center is read from IRC Table R702.3.5 and the Gypsum Association application standard GA-216. Minimum screw lengths come from GA-216 Table 5.

• Mud, tape, bead and texture

  Each product's own submittal

  Compound coverage uses the published rate for each product: about 10 gal of USG All Purpose per 1,000 sq ft of board, 9.4 gal of Plus 3 and 52 lb of Easy Sand setting compound. Tape roll lengths, corner bead stick lengths and texture coverage come from the USG, ClarkDietrich, Trim-Tex and ADFORS documents listed below. Where no manufacturer publishes a figure, as for a skim coat of thinned compound, the page says so, shows the arithmetic and lets you change it.

• Code requirements

  The code text itself

  Garage separation, floors over basements, under-stair enclosures and foam thermal barriers are read from the 2024 International Residential Code (R302.6, R302.13, R302.7 and R303.4) and compared with the 2021 edition where both are in use. Manufactured homes follow the HUD code, 24 CFR Part 3280. Every code page says that your state or city may adopt a different edition or amend it.

• Labor wages

  BLS Occupational Employment and Wage Statistics

  Wages for drywall and ceiling tile installers (47-2081) and tapers (47-2082) are copied from the BLS May 2025 release as published, for the nation and each state, with nothing estimated. Where BLS does not publish a figure for a state, the page says so. The labor cost per square foot is the site's own planning range, scaled by how a state's wage compares with the national one, and it is labeled that way.

• Screws per pound

  Published box counts

  Screw counts per pound come from Grip-Rite's published quantities for #6 coarse-thread drywall screws: 258 per lb at 1-1/4 in, 200 at 1-5/8 in and 175 at 2 in. The screw calculator turns your screw count into pounds and 1 or 5 lb boxes with those figures, and says that other brands vary.

• Prices

  Your own local prices first

  The calculators ask for your price per sheet and labor rate rather than assuming a national average. Where a page quotes typical costs, it cites the cost guide it took them from and shows them as a range, not a quote.

• The arithmetic

  Automated tests and worked examples

  The room geometry, the sheet layout engine and every material calculator are covered by automated tests, and worked examples quoted in the articles are run through the calculators so the prose and the tools agree.

Model codes and manufacturer instructions change, and local codes amend them. When a page explains a code rule, it names the edition and section so you can check it with your building department, and it treats local code and the product's current instructions as the final word.