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bouncy floor


muddman's Avatar
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10-13-04, 10:22 PM   #1  
muddman
bouncy floor

I recently purchased a 90 year old home and am doing a gut rehab. One thing that I have not been able to fix is the very bouny floor on the main level. There are 2x8 joists 16" apart that had a twenty foot span across the two biggest rooms. I put a support beam of three 2x6's nailed together with support beams about 8 ft apart. It helped, but the floor is still very bouncy. All i have to do is stomp a little and the whole floor and walls shake. There is no rot in the floor, everything seems to be tight against the sill plate and existing support beem. the floor is warped in places, but nothing huge. What do I need to do? Am I going to have to re-enforce the joists themselves? better support beam?

 
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10-14-04, 02:33 PM   #2  
Crawl space or basement?

Do a complete inspection of the joists from the crawl space or basement. A 1910 house I once owned had joists cut by a plumber running a waste line, causing a bouncy floor. There could also be insect damage inside one or more joists. Or the ground may have settled underneath one of the footings, as houses built back then sometimes had footings sitting on bare earth. The cause will determine the correction.

 
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10-16-04, 10:49 PM   #3  
The "girder" you assembled needs to be supported as follows and the top of the piers should be 6" above grade.

However, for this to be completely effective, it needs to be to fully "loaded".
Using level lines and jacks will sufficiently accomplish that. Then to complete, solid block between each floor joist directly above the girder.

(A pier foundation is simply an individual footer that supports a structural post or beam. Simple pier foundations are commonly used for small structures built with a crawl space design. Anchor bolts or plates are usually set in the pier footer before the concrete sets. This makes attaching the post or beam much simpler and results in the strongest possible application.

Pier foundations should be set deep enough in the ground to avoid shifting and upheaval caused by freeze/thaw cycles. A truncated pyramid shape saves on the amount of concrete used. Forms can be constructed of plywood or other sturdy lumber.)

 
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10-17-04, 06:43 AM   #4  
Right Idea Wrong Solution

Posted By: muddman I recently purchased a 90 year old home and am doing a gut rehab. One thing that I have not been able to fix is the very bouny floor on the main level. There are 2x8 joists 16" apart that had a twenty foot span across the two biggest rooms. I put a support beam of three 2x6's nailed together with support beams about 8 ft apart. It helped, but the floor is still very bouncy. All i have to do is stomp a little and the whole floor and walls shake. There is no rot in the floor, everything seems to be tight against the sill plate and existing support beem. the floor is warped in places, but nothing huge. What do I need to do? Am I going to have to re-enforce the joists themselves? better support beam?

You had the right idea about strenghthening the floor by shortening their spans with a center beam, however, you center beam is too small to handle the load.

The center beam should have been built with at least 3 2x10s with posts spaced at 8' or less to achieve desired results. 2x6s are far too small to help with this load.

The result is that you have an undersized center beam for the load.

Increase the beam size and you should be able to stiffen the floor for desired results.

Consult your local code office for their direct recommendations on spans and beam/header sizes.

 
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10-24-04, 09:56 PM   #5  
muddman
re-do

I will do it again with 2x10's and block between the joists when I am done.

One more question though.

Eevn now if I jump up right on top of where there is a support post, I get significant rattling of the floor and surrounding walls. Do I just have "loose" floors or walls? Is this symptom of a bigger problem?

 
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