Acceptance
By using DeckMath (the "Service") at deckmath.com and any subdomains, you agree to these Terms of Service. If you do not agree, do not use the Service.
Free use
DeckMath is free to use for personal and commercial purposes (including contractor and tradesperson use). No account, no subscription, no paywall. We reserve the right to monetize via advertising and affiliate links — those do not require any action from you.
Disclaimer of warranty — calculations are estimates
DeckMath calculators are estimates and educational tools, not stamped engineering documents. They are based on:
- Prescriptive tables published in IRC 2021 (joist span, beam span, footing diameters, stair geometry, guard spacing).
- Manufacturer-published coverage and pricing data (Trex, TimberTech, Cabot, Behr, etc.).
- National-median labor and material pricing from RSMeans, Home Depot, Lowe's, Home Advisor, and Angi (2026-Q1).
Real-world results vary based on local market conditions, contractor skill, weather, soil, and many factors outside the calculator's input set. Always confirm with:
- Your local building department, before pulling a permit or breaking ground.
- A licensed structural engineer, for any non-prescriptive design (cantilevers beyond 1/4 of joist span, irregular load paths, decks attached to cantilevered house framing, multi-tier or wraparound decks above 8 ft).
- At least 3 contractor bids for project pricing — DeckMath should land within ±15% of the bids you receive in most US markets.
THE SERVICE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
Limitation of liability
IN NO EVENT SHALL DeckMath, SemiSoftwares, OR ITS OPERATORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, SPECIAL, OR EXEMPLARY DAMAGES (including but not limited to permit denial, failed inspection, structural failure, project budget overrun, or contractor disputes) ARISING FROM YOUR USE OF THE SERVICE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
To the extent any liability cannot be excluded by law, our total aggregate liability shall not exceed USD $50.
Embed widget usage
You may embed DeckMath calculators on your own website using the embed script provided on each calculator page. Embed usage is permitted under:
- 1,000 calculations per hour per domain (free tier).
- Required: leave the "Powered by DeckMath" link in the embed footer.
- Prohibited: removing the DeckMath logo or modifying the iframe content via DOM injection.
- Prohibited: re-hosting calculator code on a non-DeckMath domain (this is the embed iframe's purpose).
Need higher rate limits or a white-label license? Email [email protected].
Intellectual property
DeckMath calculator code, designs, content, and graphics are the intellectual property of SemiSoftwares unless explicitly noted otherwise. Brand names referenced (Trex, TimberTech, Fiberon, Cabot, Behr, Olympic, etc.) are trademarks of their respective owners; DeckMath is not affiliated with or endorsed by any of these companies. We reference brand products to provide accurate pricing and specifications to our users.
IRC 2021 references are to the International Code Council's publicly published prescriptive sections, used under fair use for educational purposes.
Acceptable use
You agree not to:
- Use the Service to violate any applicable law or regulation.
- Attempt to scrape, replicate, or systematically download calculator results at scale (use the embed iframe instead).
- Probe, scan, or test the vulnerability of the Service or any connected systems.
- Distribute malware, phishing content, or any disruptive content via the Service.
Affiliate disclosure
DeckMath may participate in affiliate programs (Home Depot via Impact, Lowe's via CJ, Amazon Associates, Trex Pro Platinum, etc.). When active, we may earn a small commission on purchases made through outbound links. Affiliate participation never affects which products we recommend — we recommend the best product for the job, then add the affiliate tag if available.
Changes to these terms
We may update these terms periodically. The "Last updated" date at the top reflects the most recent change. Material changes will be flagged on the homepage for at least 30 days. Continued use after a change constitutes acceptance.
Governing law
These terms are governed by the laws of the jurisdiction in which SemiSoftwares is registered. Any dispute that cannot be resolved amicably shall be subject to that jurisdiction's courts.
Contact
Questions about these terms? Email [email protected] or visit the contact page.