Add More Support Under Your House

by Peter Bales | 15th September 2010

For whatever reason, many homes could use some extra support under them.  For many older homes, the floor joists may be weakend due to water damage or even people making notches for pipes in the wrong place.  It commonly comes up on home inspection reports, which happened to the homeowner who called me for today’s project.

One side of the home used 2×10 floor joists, 16″ on center, spanning 14 feet from side to side.  With strong lumber, this should be adequate for most flooring but much of the floor above was ceramic tile and we wanted to strengthen things up a little.  The plan was to reduce the span of the joists, by adding additional supports across in the middle. 

Doing anything in a crawlspace is always more challenging.  Today’s crawlspace was unusually hard to get into.  As you can see in the picture, there were two huge HVAC ducts running through the access point leaving only a little gap for me to squeeze through.  Yikes!  Thankfully, the homeowner had a friend who joined me for the day and made all the cuts and handed pieces down to me.  I just stayed under the house.

Somewhere along the way, a previous homeowner had added some flimsy supports trying to strengthen things up.  You can see in the picture below that there were many problems with their work:  1) They didn’t use treated lumber and boards rotted, especially at the bottom, 2) Once they rotted, they weren’t holding anything.  Perhaps the biggest problem with adding a single support like they did is that it only supports one joists.  If you aren’t careful, over time, you’ll end up with a noticable hump in this area.  Instead, we want to support all the joists evenly.

The old rotten supports.

The better method is to install some large 4×6 beams across many joists supported by a 4×6 post set on a solid concrete block (or footer, if you’re ambitious).  Home inspectors like this better than the adjustable jacks posts.  These jack posts are not really supposed to be a permanant fix.  Using a 4×6 post is also cheaper because the adjustable jack posts start at $30 each!

Once you’ve made it into the crawlspace the hardest part is how to hold the beam in place while you get the posts installed.  Having a helper is always a good idea, but I was working alone down there today.  I started off by making a couple brackets out of 2×4 scraps that I could screw to the joists.  These would hold the beam in place while I got the posts cut and installed.  This worked great, however, I also found that the adjustable stand that goes with my miter saw would fit down there and hold one end of the beam.  It was great in my case, but it depends on how much room you have to work with.

Hold that beam up!

 
When cutting the posts it’s great to be exact with your measurements, but often there will be a small gap.  Instead of cutting another piece, you can use metal shims to get the beam up as high as you want it.  Metal shims are better than wood because they won’t deteriorate over time and you can really hammer them to get them in place.  By the way, these shims are not wedge shaped like cedar shims for installing a door, these are just thin, flat pieces of metal.  I was able to buy as many as I needed for around $1.50 each, depending on how thick they are.

One of many supports.

Once I had the posts plumb and had everything in position, I screwed it all together using 3″ deck screws meant for treated lumber.  I screwed the posts to the beam and put a screw through the beam into each floor joist.  This ties it alltogether, adding strengh and even more stability to the structure.

Aren’t you glad that I took all these pictures so you didn’t have to go down there to see what I was talking about?  You can thank me later. :)

2 Responses to “Add More Support Under Your House”

  1. Mark

    Sep 16th, 2010 :

    thanks Peter, good job – it looks GREAT!

  2. Todd

    May 10th, 2012 :

    looks good Peter. I myself and trying to replace floor joist supports that were put there by the previous owners…mix of 2×4 and 2×8 post supporting 2×4 “beams” must have been on a budget… anyway i put in temparty jackpost and removed the “supports” to give me room to dig footings for perminate post. i was going to use 4×4 as post and beam but it seams that they have a tendicy to bend alittle more than i want. 4×6 does the tick and elimanates a few post.it was just alot harder to handle on my back bymyself.i like how you use the 2x hangers to hold it up in place…alot better than my method head in the center and pray you can get the supports under before i drop it.. Also i have had to double up my floor jost due to the fact that they are 2′ oc. and it is supporting a full bath room. Crawspace work is never fun…..good job

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