sagging/springy floor!!!

Postby muffs11 » Wed Sep 05, 2007 4:41 pm

Q: My husband and I live in an 1850s 2 storey house Floor joists for the second-floor bedroom are 2x6s that span 12 ft. The joists have a definite sag to them (more than 1-1/2 in. in places), and the floor is like a trampoline when walked on. We are thinking of jacking the floor from underneath to take out the sag, then beefing up the joists. Do you have any suggestions?
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Postby gabysdad » Mon Oct 01, 2007 3:07 am

If you can access the joists from below, it would probably be a good idea to install larger joists, such as 2x10 or 2x12s. you could attach them to the existing joists with carriage bolts or lag bolts. just jack up the joists until the floor is level, then install the new joists to beef up the floor. i hope this makes sense. all of this is dependent on the ceiling height in the first floor.
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Postby rosebery » Mon Oct 01, 2007 6:52 am

Has this happened since you bought it? Get it structurally looked at.

Have you bought it recently? If yes what did the survey say?

This is not DIY stuff! Get someone in.

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Postby thedoctor » Tue Oct 02, 2007 7:36 am

Take a look at our projects section with regard to levelling floor joists and repairing structural timber. Its perfectly possible using the correct techniques to DIY.

Use also our Floor Joist Spans project to see how big the joists "should" be, regulations have changed a great deal since 1850 and it would be as well, and probably a lot cheaper, to insert proper sized joists. It is possible however, using our projects on structural timber, to insert reinforcing into joists leaving them stronger than the original. If you telephone the sponsors of this project, PRS, they will give you free advice over the telephone and they do so with absolutely no obligation on your part.
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Postby LCL » Tue Oct 02, 2007 5:35 pm


As a rule of thumb, imperial joists should be half the span plus 1. Therefore a 12ft span = 6"+1" = 7 x 2s. Current building regs for this span (3.6m) is a 50 x 170 C16 joist.

Depending what is below it may be just as well to support a steel beam at mid span. This may require a party wall agreement if your are loading onto a party wall. You will also need building regulation approval and an engineer to design a steel beam.

I do not see the merrit in jacking up the floor joists personally. If you remove the floor covering, install new joists of a correct size and re-cover the floor and new ceiling below, the old saggy joists will be totally redundant. This will require quite a bit of work so the steel beam may be more appealling, but will result in a down stand to the ceiling below.

Hope this helps

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Postby kimmey » Tue Jul 01, 2008 7:36 am

I'm currently moving into my brother’s old room, and the floor needs to be repaired and sealed before I can place a wood floor of my choice over it. Since it's such an old house the boards run long ways, and a few are broken at the ends, and he smoked so the wood in the floor smells. How can I repair the floor and seal all the smell of smoke, so I can place the new flooring over it with out any problems in the future?
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