Lifting Up a Sagging Floor DIY Old House Crazy

Lifting Up a Sagging Floor DIY

Cost, Time, and Skills:

This job took two people one afternoon. We got muddy because we were in a dirt crawlspace doing just that, crawling. We used 18,000-pound screw jacks, 44 lumber, a circular saw, power drill/driver, and cement blocks. Total cost was less than $200, while a pro would charge $500-$1000.

This past Saturday, my brother had me over to help move some of his furniture during the annual rearranging of the tv room. The photo below shows what we saw when we moved the couch away from the wall.

Look for the 1 inch gap between the floor and the base board

Apparently, its been that way since they bought their 90-year-old bungalow and its been nagging at my brother ever since. You may have similar areas in your home. You probably feel the same way my brother did: its not THAT big a deal and itll cost at least $1000 to repair, so lets buy diapers and food and gas with our money instead. Well, it isnt THAT big a deal now, but it could develop into a whole host of problems down the line, especially if the sagging is caused by a larger issue.

Three 18000 lb screw jacks and solid concrete blocks for support

The truth is, it will cost you upwards of a thousand dollars to hire professionals to do anything to your foundation or the under-structure of your home. Just plan on that. Plus, its hard to find the right people to do this work, because it requires on-site problem solving and a certain amount of risk assessment (dont hire anyone that seems kind of stupid). I know this. We paid to have some work done on our sill plate last summer and it hurt the wallet. A lot. However, watching the crew work on my house let me know that I could certainly do that work myself the next time the need arose.

We ripped the 210s in half to make four 4 ft joists

As a homeowner with an eye for and interest in how things work, Ive learned an extremely important thing: my house is actually really simply built and nothing in here is all that complex. The trouble is knowing what to do and what tools to buy. If you arent good at figuring stuff out on your own, hire someone. once. While theyre working, ask them questions about the process and about what theyre doing. Assess whether you think you can do it yourself. I learned most of my skills out of necessity (its a cash flow thing) and by watching professionals.

As with many old houses, my brothers has a tiny crawl space door. Im large so that makes me unhappy.

For this job, as with any job, we first needed to figure out what the root problem was. The sagging floor was the symptom, and somewhere under the house there had to be a cause. Well, after doing the navy SEAL crawl up under the house, we found that the joists that were supporting that floor were not actually attached to the sill plate any longer, as seen in the photograph below. This is an obvious problem, considering the fact that the sill plate is the first line of support above the foundation wall. You can see that the joist had dropped about an inch below the sill, explaining the inch the floors had sunk.

The joist had slipped about an inch from the sill

In order to lift this section of flooring back up an inch, we needed to purchase a few screw jacks, which can be purchased at your local big box hardware store for about $30 per jack. The ones in the photos above are actually not the ones we ended up using. We had to buy shorter ones. But hey, whats a home improvement project without at least two trips to the store?

Moving around under old houses can be tricky. My brothers crawlspace opens up quite a bit once youre inside. It used to be a dry cellar for storing produce during the summer, with a trap door in the kitchen.

As you can see in that last photo, my brothers crawl space is rather spacious in spots. Unluckily for us, the spot we were working wasnt one of the spacious ones. Here he is squeezing through the little trap door. Note the coveralls. Id recommend covering yourself when working under the house. Its nasty and there are spiders and junk.

A gift my brother and I both possess: flashing a goofy smile at a moments notice.

Heres where we were working. The 2×8 joists you see in the photo (the boards running from left to right above my brother for the lay men) are the ones we would be supporting. We decided that we wanted to sister a new 2×10 board up against the existing joists and support the new joists. We chose this method because of the small amount of old termite damage we saw in some of the old joists. What we did was lay the new board flush with the floor boards and with the old joist. We then fastened the two boards together with 3 inch wood screws.

Lifting Up a Sagging Floor  DIY Old House Crazy

The crawlspace was really tight in the area we were working. Luckily, it was pretty dry. The vapor barrier and outside drainage had done their job well.

Below, you can see my brother prepping one of the new joists by partially driving the screws into the wood. This is surprisingly difficult to do when holding a twenty pound joist and a drill above your head while lying on your back.

I used to balk at the drills and power tools that come with a light. Not any more. That little light came in very handy.

With the mud and the muck, I didnt get any photos of the next step or two. In the photo below, you see the final product. You can see how the new joists are attached and, if you look towards the background, how they overhang the old joists so the support beam is only pushing on the new joists.

Heres the completed job. The new joists are attached to the old joists and are supported by the 44s and screw jacks.

Once the new joists were up, we found locations where the concrete blocks could sit flat on the ground so the pressure wouldnt cause them to crack. After they were in place, we hoisted up the 4x6x8 beam so that it crossed all four of the new joists, sliding the screw jacks underneath. With the beam resting nicely on the jacks, we slowly turned the red handles until the beam was in contact with two of the joists. Then we kept turning until it was in contact with all four of the joists (the lower two lifted up to be in line with the higher two). By yelling through the floor to my brothers wife, we were able to coordinate our slow turning of the screw jacks until the crack between the floor and the base board was gone.

Heres the final product. Total, this  job cost my brother $150-$200, where a pro would easily have charged $800-$1000. Ill admit, this is probably not the job for a first time do-it-yourselfer, but folks with a little experience and confidence can easily repair the sagging floors in their homes.

Look for the 1-inch gap between the floor and baseboard. Its not there any more.

The before and after is below. If youve got questions or comments, leave them below or contact us at Also, feel free to leave us a comment on our facebook page Thanks for reading. -Robby

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