Adjust floor joists, tips and advice

[eddiw]

I have a house from the 1940s where we've torn out the old floor in a room and will replace it with floor chipboard and new flooring.
The problem now is that the joists are not straight, so I need to level them.
There are different solutions for that, such as attaching new joists alongside the old ones and then leveling them. You could also try placing something on top of the existing joists.

But what is the best and most convenient way to do it? If one were to install joists on either side of the existing joists, what dimensions are needed for the joists?

If one were to try to place something on top of the existing joists, what material can be used to reach the correct level on the joists that are lower?

 

[Småbrukaren]

Available spacers, plastic shims, even wooden wedges work.

The dimension of the lumber naturally depends on the load, is it the ground floor with a basement underneath or the floor on the upper level?

 

[fribygg]

I have a house from the 40s where we have torn out the old floor in a room and will replace it with chipboard and new flooring.
The problem now is that the joists are not straight and I need to adjust them.
If you were to try to lay something on top of the existing joists, what material can you use to level the joists that are lower?

Adding some masonite strips where it is low is classic if you are not adjusting the entire joist system.

 

[kniv]

Adding a masonite strip where it's low is classic if you're not leveling the entire joist system.

On the joist system then, between it and the floor particle board? Doesn't the gluing weaken quite a bit if you screw-glue?

 

[fribygg]

On the beam then, between it and the floor chipboard? Doesn't the gluing weaken quite a lot then if you screw-glue?

Traditionally, tongue and groove wooden floors are nailed in such houses as far as I know, but it should work fine with a wood fiber strip under the floor chipboard if you cannot or do not want to take up the beam and level the floor.

 

[Jontha]

Forget about the hardboard strips, it just gets messy and tiresome. I guess you have 240 studs now. You can probably go down to 120 on the ones you attach next to them. When you plane, it's really not great to have hardboard strips underneath. If you're going to nail tongue and groove boards on the floor, you might as well let the floor stay as it is today. Nails and boards = squeaking eventually.

 

[kniv]

Classically, wooden floors are spontaneously nailed in such houses as far as I know, but it probably works fine with a masonite strip under the floor chipboard if you can't or don't want to remove the joists and level the floor.

The TS wanted to lay floor chipboard, not nailed wooden flooring?

I have a house from the 40s where we've torn out the old floor in one room and are going to replace it with floor chipboard and a new floor.

 

[fribygg]

OP wanted to lay chipboard flooring, not nailed wooden floors?

I could only see that OP wants chipboard flooring and a new floor on top of it, not which material or fastening method.

 

[fribygg]

I have a house from the 40s where we've torn out the old floor in a room and are going to replace it with chipboard and new flooring. The problem now is that the joists are not straight, so I need to adjust them. There are different solutions for that, for example, adding new joists alongside the old ones to level them. You can also try to place something on top of the existing joists.

But what is the best and most efficient way to do it? If one were to joist on either side of the existing ones, what dimension is needed for the joists?

If one were to try to place something on top of the existing joists, what material can be used to reach the correct level on the lower joists?

What surface material are you planning for the floor? If you are planning linoleum, tiles, or vinyl, you can probably fix the unevenness in the subfloor with self-leveling compound.

 

[Gabbe1]

Considering how quickly you can weigh off and glue screw new studs onto the old ones, I think it's a non-issue. Additionally, you get a significant reinforcement of the floor framing, which results in less deflection.

 

[kniv]

Given how quickly you can level off and glue-screw new joists onto the old ones, I think it's a non-issue. Additionally, you get a proper reinforcement of the floor structure, which results in less flex.

The downside is that the compartments reduce, so all insulation must be cut...

 

[Gabbe1]

The downside is that the compartments decrease so all insulation must be cut..

A non-issue in a house from the 40s, where there is shavings in the joists.

 

[eddiw]

A non-issue in a 40s house, where there is sawdust in the joists.

Thanks for all the responses! There's been some illness here, so I haven't gotten around to it yet. The sawdust in the joist has been removed and replaced with stone wool in this case, though. But not too hard to cut it so it fits.

I'll think a bit about whether I should use furring strips or lay hardboard strips. There's a slight difference between the joists, but enough that the floorboard doesn't like it. The joists are a bit crooked and warped, so it's not very easy to attach new joists to the old ones without them also becoming slightly angled. And next to one wall, there are only planks used as a joist with some shimming of blocking underneath, as the beam appears to lie under the wall. Always fun in these 40s houses... Nothing is easy.

 

[mattias.rask]

Thanks for all the replies! There has been some illness here so I haven't gotten around to it yet.
The chip in the joist space has been removed and replaced with stone wool in this case, though.
But it's not so hard to cut it to fit.

I'm considering whether to raise the framework or lay a hardboard strip. There is very little difference between the studs, but enough that the floor chipboard doesn't like it.
The studs are a bit warped and twisted, so it won't be easy to fit new studs on the old ones without them also being angled a bit. And next to one wall, there are only planks used as studs with a bit of spelling with noggings underneath, since the beam seems to be under the wall.
Always fun in these 40s houses... Nothing is easy.

How did it go? I'm in a similar situation.

 

[eddiw]

How did it go? I am in a similar situation.

The stud against the wall, which was excessively high compared to the others, I lowered slightly by using a multitool. That stud was the most troublesome. For one stud, I attached a thin plywood piece to raise it a bit, and the third stud I planed with an electric planer.
It turned out much better than before and there were no issues laying the floorboards after that. 😊

It didn't become perfectly straight, but significantly better than before. Now it's not noticeable like it was before; only the spirit level shows that it's not perfectly straight.

The initial thought was to install new studs, but there was no way to do that if the floorboards were to fit, as the floor would have ended up higher than the floor outside the room, which wouldn't have been good.

After reinforcing with a laminated beam from underneath and gluing and screwing the floorboards, the floor is solid, no bounce. 👍