Messages and Online Forum Q&A

Re: Sagging floor

From: info@builderswebsource.com
Category: Structural
Remote Name: 63.198.181.43
Date: 20 Jan 2002
Time: 01:00 PM

Comments

We ran some preliminary structural calculations and, if we understood your situation correctly, the results indicate that your floor joists do not meet minimum building codes.

Here are the basic assumptions we made:

1) Joist span = approx 20 feet (including load-bearing ends)

2) Joists = 2x10 on 16" centers (assume Hem Fir or Douglas Fir - Larch)

3) Live load = 40 PSF, dead load = 10 PSF (minimum code)

4) Minimum deflection = span/360 (live load) and span/240 (total load). This is minimum code.

BeamChek shows that for this span, you need at least (3) 2x10 or (2) 2x12 for each joist to meet minimum building codes. Using only single 2x10's as you describe, the deflection is nearly 3x the allowed limit.

As a result, you could have a serious structural problem that needs immediate attention. For a home only 8 years old, this kind of structural problem is inexcusable. Are you the original owner?

We recommend that you consult with the city who issued the building permit, approved the plans and performed the original inspection. Discuss your situation. You may need to consult with an attorney to determine what kind of legal recourse you have.

As to the remedy, if the existing joists are 2x10's, you will need to add at least 2 additional 2x10s (approx. 20 feet in length) with a minimum of about 2 square inches of bearing surface on each end. These 2x10s should be bolted together with 5/8" lag bolts alternately staggered approximately every 16" along the face.

Keep in mind that you may also have plumbing and electrical wiring in the way, which could be further weakening the existing joists.

Finally, it is always difficult to interpret structural problems over the Internet...and the above recommendations do not account for other factors, such as roof loads and other point loads that may further deflect the floor. The above calculations are merely a baseline to confirm that your existing joists are way out of spec assuming our interpretation of your condition is accurate.

We always recommend that you consult with a licensed structural engineer and we would accept no other substitute in a situation such as this. The engineer can examine the as-built conditions as well as verify your assumptions. A suitable remedy can then be prescribed, which could range from the addition of LVLs, steel beams, or additional 2x material to stiffen the floor. Please keep us posted on your situation.

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