replacing termite eaten center beam?

[2manyrocks]

Well, the termites have eaten up the center beam of my parent's house. They used rough saw oak lumber because that was the only lumber they could find after WWII. It's a single story house. The beam consists of 3 oak boards nailed together. Each is 1.5"x9.25." The floor joists run past one side of the center beam far enough that my current plan is to build a 2x4 wall 16" OC under them. The wall will rest on a pressure treated 2x4 plate on the concrete floor with a doubled top plate.

Since the walls are plastered, I need to minimize the amount of lift used to get the weight off the existing center beam. One problem is that the beam has already sagged over an inch in the very center of the house.

In cutting the studs for the temporary support wall, how much longer should I cut them to get the weight off the existing center beam? I figure the weight of the building will compress the wood in the top plate and the plate resting on the floor, too. I'm not sure whether to cut the studs say an extra 1/4" too long to start with or whether that is going too far.

I'd like to correct the 1" sag in the center while I'm at this, but am having a little bit of apprehension about fixing a bunch of broken wall plaster later if I go too far.

 

[pmsmechanic]

I would be tempted to just use a temporary beam and teleposts and slowly lift the house back to where it should be, Then remove the termite eaten beam and replace it.

 

[cmyoung2]

Use some basement jacks for the temporary support. since they are screw adjust, you can fine tune how much you lift. If you need to leave in place, just build a wall around them.

 

[2manyrocks]

The beam is about 30' long with two support posts. The center part of the beam is 112". How big and long of a temporary support beam are we talking about? A temporary support beam would tend to spread out the load of the floor being raised into position without so much plaster damage compared to raising one floor joist at time? I assume I'd have to at least work in 10 foot sections. How many jackposts would be needed?

This is the good side of the center beam. The back is eaten up.

 

[pmsmechanic]

I already see one telepost (jackpost) in the picture right on the right side. You could probably get away with three but four over the 30 feet would make the job a lot easier. I would check a rental place to see if they have something you could rent if you don't want to buy.

A house mover might have a beam you could use temporarily.

I would be temped to do the whole thing at once instead of in sections. There would be less damage to the plaster. See if you can't get a 6x6 or an 8x8 treated post long enough to use as a beam. If you are planning on leaving the beam up there the bonus is that termites don't eat treated wood.

 

[doxford jim]

Just a thought but would a metal "I" beam be better for the work you intend doing. I doubt that it would sag under load if a deep beam is used. You can put as many or as few jacking posts in as you see fit. This would allow very controlled adjustment and be versatile is use.
As I said, just a thought. If you are going to try and fix the sagging, you need something that just won't move when put in place.

 

[BeezFun]

I had similar problem in an old house only it was powder post beatles that ate it up. I used shoring jacks and short pieces of 4x4 on each side of the damaged beam to raise floor joists slowly. Using short pieces allowed me to avoid conduit and other obstacles. I lifted them about 1/8" every few days until it felt like I was doing more damage than good. I had a steel beam made the right length, and put it under the damaged beam. I used a few telescoping columns along it's length, and dug holes in floor for concrete support piers to rest them on. I had to do a lot of shimming on top of the steel beam because the wood beam wasn't straight. My buddy is an engineer, he sized the beam for me but you could find tables online that will tell you how big to make it.
I would not try to remove the damaged beam, the floor joists will be toenailed into it and you'll just make a mess trying to tear it all apart.

 

[2manyrocks]

I figure I will have to use a sawsall with a nail cutting blade to saw out the old beam. It is so eaten up that I feel like it has to go.

My research is that a 4x8 I beam ought to carry the same load as the built up oak beam. But 30' of it will weight close to 400 lbs.

I do have some heavy scaffolding that was formerly used as concrete staging with the screw jacks. I wasn't sure if I should try to use it or not. The cross bracing would seem to make it less likely for a post to jump out.

 

[BeezFun]

I figure I will have to use a sawsall with a nail cutting blade to saw out the old beam. It is so eaten up that I feel like it has to go.

Well that will certainly give you a cleaner job.

My research is that a 4x8 I beam ought to carry the same load as the built up oak beam. But 30' of it will weight close to 400 lbs.

It looks like the existing beams are supported at about 10'. I assume you'll use those same supports for the steel beam, which means each piece is about 10', which shouldn't be too bad. A 4x8 beam 10' long seems reasonable to me. My basement has a 5x8 on 13' centers, but it really depends what that beam is supporting above.

 

[Cat_Driver]

Yep that was my thought. A nice Steel I beam
Also
here

How to change a one-ton beam on your own! - YouTube

AllianceCarpentry's channel - YouTube