Joists 'on a kilter' - levelling would create lip to room - what to do?

Joined
28 Jan 2021
Messages
14
Reaction score
0
Country
United Kingdom
Hi,

So got a little bit of a problem that I'm not sure how to tackle.

I'm renovating my bathroom, the floors been up for ages and I decided to lay a new subfloor as the old planks had had it.

I am not checking the level of the joists and whilst I expected them to be a bit out as it's an old house they are actually far more out that I imagined.

Here is a picture with a laser level showing the problem.

3zWhbFK.jpg


The beams are also a bit higgledy piggledy between themselves as well (i.e. they do not drop evenly from one to the next).

As it's a whole floorboards width by the time it gets to the middle of the room in order to level it up by adding height to the joists as they go to the right it would create a 18+mm lip on entering the bathroom, which is far from ideal.

I only plan on laying LVT over the top of it so my most immediate reaction is to just say sod it and screw down the ply over the top and have an uneven floor, although I'm not sure if that would cause other problems... should I attempt to get it flat even if I can't get it level - so it would slope as it goes from the left to the right (as per the photo) but the boards themselves would be 'flat'?
 
Sponsored Links
The joist to the left is at floorboard height. So what you need to do is fit a 2 x 1 lathe to the inside of the joist down by the thickness of the floorboard. Cut and fit floorboards to fit between the first two joists onto the lathes. As you work to the right, the height of the floorboards will protrude above the joists, so fit a thin bit of ply over the joist. Then as you work along further to the right, You may just want to rebate the floorboards slightly as opposed to fitting thicker ply to the top of the joists. Then to the right, looks like the floorboards will sit on top of the joists.
 
Hi Bonni,

I'm not sure I totally understand - the existing floorboards were removed completely, they had been cut into many times before, many were split and virtually all of them warped in one way or another.

The plan was to lay 18mm ply directly on top of the joists.

If I am following you correctly, are you saying I should essentially cut the ply to size and lay it between the joists for the first three joists or so until the ply can actually be layed on top of the joists to the right?

If I do it this way should I then cover the whole floor with an additional layer of ply in order to achieve a flat surface?
 
Decide on a line - either level or on an incline as appropriate and then fix some new CLS timber to the sides of those joists to the chosen line

upload_2021-12-9_19-58-10.png
 
Sponsored Links
Right, I think I've got it, so I can have it slope from the right side to the left, but need to get an evenly supported slope from one side to the next by sistering the joists as per your photo?
 
Yes, a slope is OK and less noticeable than an up-and-down surface. As shallow a slope as you can, but take account of that door swing too if the surface is going to be higher on the right.
 
Great, thanks.

As it's a bathroom there is going to have to be a gap under the door for airflow in any case (I need to take some material off of the bottom of the door), so there should end up being plenty of clearance!
 
Don't worry too much about the slope. You prob never noticed it before you lasered it. If you are going for LVT what matters is flatness - any hump or dip and you will fight the flooring and never get it laid nicely. If you do have a hump or dip you can't get rid of consider using ceramic tiles instead. You can usually pinch a smidgen on each of the joints enough to get over a little un-flatness.
 
Hi Bonni,

I'm not sure I totally understand - the existing floorboards were removed completely, they had been cut into many times before, many were split and virtually all of them warped in one way or another.

The plan was to lay 18mm ply directly on top of the joists.

If I am following you correctly, are you saying I should essentially cut the ply to size and lay it between the joists for the first three joists or so until the ply can actually be layed on top of the joists to the right?

If I do it this way should I then cover the whole floor with an additional layer of ply in order to achieve a flat surface?

Ok, just like in the picture, fit the timbers lower by the thickness of the floorboards or ply. Cut the floorboards or ply so they span within the joists (short ways) and rest on the wood that you fitted as per the picture. So where the joists are too high, the joists and those lowered floorboards/ply are at floor level. So your floor on the left is now at the correct height.

As you move extreme right, it looks like the floorboards/ply fitted to the top of the joists would be at the correct height. So as you work from left to right, your floorboards/ply will appear above the top of the joists, so you can make up that gap on top of those joists with thin ply etc.. Another trick is to rebate the floorboards/ply, so thin those where it touches the joists with an electric planer.

Hard to explain just in words.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top