Disclaimer
Disclaimer: what these construction calculators are, and are not
Every result on this site is a lookup in a published code table or a piece of geometry, produced by a website, not by an engineer. It is a reference to help you plan, check a number, and talk to your inspector. It is not a design, not a permit document, and not advice from a licensed professional. This page sets out exactly where the line sits.
The calculators are reference tools, not engineering
MyBuildingCalculators.com is built and maintained by Syed Zulqarnain, a website builder and data curator. He is not a licensed engineer, architect, contractor or code official, and nothing on this site is produced or reviewed by one. The span, stair and guard tools reproduce prescriptive tables from the 2021 International Residential Code and the AWC DCA 6-2015 deck guide, as printed, and the quantity tools do arithmetic on the dimensions you enter.
Using this site creates no professional relationship of any kind. A result here does not certify that a member is adequate, that a stair is compliant, or that a design will be approved. Only a licensed design professional and the building department with jurisdiction over your property can do that. Treat every number as something to verify, not something to rely on.
What the calculators do
- Reproduce IRC 2021 span tables for floor joists, ceiling joists, rafters, headers, deck joists, deck beams and deck posts, and the AWC DCA 6-2015 footing table, and report the cell that matches your inputs.
- Snap every input up to the next printed value in the table. Nothing is interpolated or extrapolated; a result past the end of a table says so instead of returning a number.
- Check stair, ramp and guard dimensions against IRC 2021 R311 and R312 limits.
- Calculate quantities, areas, lengths and counts for concrete, roofing, tile, drywall, lumber, fencing and similar materials from the dimensions and waste percentage you enter.
- Print each result with its assumptions and the table, section or page it was read from, so you can check it against the code book yourself.
How each table was entered, checked and rounded is described on the methodology page.
What the calculators do not do
- No structural design. The tools look up prescriptive tables. Loads, members, connections, foundations and conditions that fall outside those tables need a licensed engineer.
- No wind, seismic, flood or soil design, and no point loads such as hot tubs, roofs over decks or heavy equipment.
- No cost, price or labour estimates.
- No local amendments. The tables are the base 2021 IRC as published. Your state, county or city may have changed them.
- No manufacturer data. Engineered lumber, trusses, LVL, composite decking and similar products are governed by the manufacturer's published values and sealed drawings, not by these tables.
- No check that materials are installed correctly, that a footing bears on adequate soil, or that anything built from a result will perform as intended.
Code editions and local amendments govern, not this site
The structural tables here are read from the 2021 IRC, using the struck original IRC text in the 2021 Seattle Residential Code PDFs and ignoring Seattle's own amendments. Many jurisdictions in the United States still enforce the 2015 or 2018 IRC, some have moved to a later edition, and nearly all adopt the code with local changes. Seattle, for example, raises the deck live load from the IRC's 40 psf to 60 psf, which shortens every deck span; this site uses the IRC's 40 psf.
The code adopted by your building department, with its amendments, is the only version that applies to your project. If a number here differs from the one your inspector uses, the inspector is right for your jurisdiction. Confirm the edition and any amendments before you order materials or cut anything.
Values you enter are your responsibility
Several calculators ask you for a figure instead of looking it up, because the reliable source is your site, supplier or building department rather than a table this site can verify. These include ground snow load, soil bearing and footing width, frost depth, aggregate density, bag coverage, grout coverage and waste percentage. The result is only as good as the value you enter. A default that looked exact but was wrong for your material would be worse than asking, so the tools ask.
Species, grade, spacing, span and load choices are also yours. Selecting a higher grade or a lighter load than the lumber and the site actually have will produce a span the code does not permit.
Errors, misprints and corrections
Every table was entered from the source PDF and checked against it, and the checks are described on the methodology page. Even so, transcription errors are possible, and the published 2021 IRC itself contains misprinted cells: eight rafter cells are defective in the printed code, seven are corrected from their twin tables and flagged in the result, one is left blank because no correct value can be derived, and some deck beam cells are withheld for the same reason; the full list is in the rafter table errata post. No guarantee is made that any value is free of error.
If a result does not match your copy of the code, report it through the contact page with the calculator, your inputs, and the table and page you checked. Confirmed errors are corrected; differences caused by another edition or a local amendment are explained. Corrections may change results without notice.
The notice printed under every result
Each calculator carries this line beneath its result and on every printed copy:
Results are for planning and estimating quantities only. They are not a substitute for a local building department review or a licensed engineer. Verify every value against the code adopted in your jurisdiction before you build.
Printing or saving a result does not change its status. It remains a reference lookup, not a stamped document.
No warranty and limitation of liability
This site and its calculators are provided as is, without warranty of any kind, express or implied, including accuracy, completeness, fitness for a particular purpose and non-infringement. To the fullest extent permitted by law, the site owner is not liable for any loss, damage, injury, failed inspection, rework, wasted material or other cost arising from use of, or reliance on, any result, table or page on this site. You use the calculators at your own risk and remain solely responsible for verifying every figure and complying with the codes and permits that apply to your work.
MyBuildingCalculators.com is not affiliated with, endorsed by or sponsored by the International Code Council, the American Wood Council, the City of Seattle or any building department. IRC and DCA 6 are the property of their respective owners and are cited as sources. Links to outside sites are provided for reference; their content is not controlled or guaranteed by this site.
Scope of this disclaimer and related pages
This disclaimer applies to every page and calculator on mybuildingcalculators.com and should be read with the terms of use and the privacy policy. It may be updated when tools, sources or code editions change; the current version is the one on this page. Questions about it go through the contact page.