Floor sloping upstairs

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There's no reason why a keen DIYer with a few tools can't do this sort of job. Prior to cheap self-levelling lasers this sort of job required string lines and 6ft levels (or a shorter, accurate level strapped onto an accurately planed length of straight carcassing) and wasn't anywhere near as easy a job to do. These days with a cheap self levelling laser and a home made wooden staff the job is relatively simple.

Easiest way is sister the joists with inch ply (rip it down to 4" or 6" wide strips) then screw your floor to the ply ededge.
I'd sound two notes of caution about this - firstly hitting an 18mm edge more or less dead centre with a screw through a sheet of plywood or chipboard isn't necessarilly that easy, especially not over the full extent of a floor, and secondly it really isn't advisable to screw into the edges of plywood because it can delaminate all too easily. In fact the quality of modern Chinese-made construction hardwood plywood is so poor that it is almost a foregone conclusion that it will end up delaminating if you edges screw, even if you pre-pilot. Something like 3 x 2in (70 x 44mm) or 4x 2in (90 x 44mm) CLS is not only a bigger target to aim at but it won't just delaminate like plywood can
 
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There's no reason why a keen DIYer with a few tools can't do this sort of job. Prior to cheap self-levelling lasers this sort of job required string lines and 6ft levels (or a shorter, accurate level strapped onto an accurately planed length of straight carcassing) and wasn't anywhere near as easy a job to do. These days with a cheap self levelling laser and a home made wooden staff the job is relatively simple.


I'd sound two notes of caution about this - firstly hitting an 18mm edge more or less dead centre with a screw through a sheet of plywood or chipboard isn't necessarilly that easy, especially not over the full extent of a floor, and secondly it really isn't advisable to screw into the edges of plywood because it can delaminate all too easily. In fact the quality of modern Chinese-made construction hardwood plywood is so poor that it is almost a foregone conclusion that it will end up delaminating if you edges screw, even if you pre-pilot. Something like 3 x 2in (70 x 44mm) or 4x 2in (90 x 44mm) CLS is not only a bigger target to aim at but it won't just delaminate like plywood can

Thank you.

I have talked to mate about the posts on here. He wants to do a proper job.

Lifting old floorboards on landing, removing skirting, trimming door frame and sistering new 'joists' to those that require more height seems to be his preferred method.

Would he have to set a laser level low down on the floor to get the correct level and can you recommend a cheap but decent laser level?

Just for curiosity, what do you think a carpenter would charge for doing this work?

A 3rd of the floor in the bedroom (pic in first post) would need to be levelled off towards the wall pictured with the cut boards too.

Thanks
 
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Would he have to set a laser level low down on the floor to get the correct level and can you recommend a cheap but decent laser level?
I think that your mate should take a similar approach to that we take on commercial jobs, namely set a datum mark and work from that. Basically mark a point on the wall in the middle of the landing at 1 metre above the floor level (a horizontal line with an arrow head beneath pointing upwards is one symbol used to mark this). The laser is then set up so that the laser line "paints" the datum line (remember, any laser line varies in thickness depending on how near or far the laser is from the wall, etc so the line yo mark or eyeball is in the middle of the laser line, not the edge - a common misconception amongst inexperienced laser users).

A setting rod is then made up from straight 2 x 1in planed softwood lath about 1100 to 1200mm long. It needs the bottom to be cut exactly square, and a very faint pencil line to be set at 1m from the bottom using the laser NOT a tape measure (see below)

How do you set up the rod? Stand the rod on the floor by the wall where the datum mark is as vertically as possible. Tilt the rod back and forth and watch the laser line on the stick. When the laser line is the lowest on the rod, that is the datum point for the floor at that point. It should match the pencil line. If not, add another pencil line to the rod in the middle of the laser line. Then emphasise the line with a thin black Sharpie and a try square. You then need to add a second thin Sharpie line on the rod which is the thickness of your flooring material (say 18mm) above the first line. Again use a try square to draw the line. If you want you can now go over the floor at different points to see how far out the floor really is

Once the floor is lifted and the sistering joists are ready to install (i.e cut to length) you start the installation by first re-setting the laser to the datum line. Always start by installing the joists furthest away from the laser and working backwards towards the laser. Each joist is installed the same way: drop into place (gently!) and fix one end lightly with a single screw at one end only at the approximately correct height, say 10mm above the joist. Then using that first screw as a pivot swing the other end up with the rod held above it until the laser line hits the upper marked line on the rod and screw that end in place lightly. Go back to the first end and check that with the rod using the waggle back and forth technique to find the lowest point. Adjust the position of the joist if required. Then go back to the first end and repeat, only this time fix it properly when it is bob on. Work back down the joist screwing the sister to it as you go until all the screws are tight. I'd recommend pre-drilling the sister and loading it with partly driven screws (driven about 35 to 40mm in at something like 200 to 300mm centres) before installation and using a 5 x 80

As they are holding the wall up, that may be easier said than done.
I think I would go with J&Ks suggestion of SLC.
Until the floor is opened up there is no way to tell. The walls which run in the same direction as the floor boards will be OK as they run across the joists - it's the ones running at right angles to the floorboards where there may be issues. Incidentally I did touch on that in post #22 and how to deal with it.

If the floor wasn't too far out I'd probably also go with a 4mm layer of plywood (150mm screw centres) and screed as well, despite the potential faffing about with the edges, but then I've not seen the job in person, and that is merely conjecture on my part
 
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I think that your mate should take a similar approach to that we take on commercial jobs, namely set a datum mark and work from that. Basically mark a point on the wall in the middle of the landing at 1 metre above the floor level (a horizontal line with an arrow head beneath pointing upwards is one symbol used to mark this). The laser is then set up so that the laser line "paints" the datum line (remember, any laser line varies in thickness depending on how near or far the laser is from the wall, etc so the line yo mark or eyeball is in the middle of the laser line, not the edge - a common misconception amongst inexperienced laser users).

A setting rod is then made up from straight 2 x 1in planed softwood lath about 1100 to 1200mm long. It needs the bottom to be cut exactly square, and a very faint pencil line to be set at 1m from the bottom using the laser NOT a tape measure (see below)

How do you set up the rod? Stand the rod on the floor by the wall where the datum mark is as vertically as possible. Tilt the rod back and forth and watch the laser line on the stick. When the laser line is the lowest on the rod, that is the datum point for the floor at that point. It should match the pencil line. If not, add another pencil line to the rod in the middle of the laser line. Then emphasise the line with a thin black Sharpie and a try square. You then need to add a second thin Sharpie line on the rod which is the thickness of your flooring material (say 18mm) above the first line. Again use a try square to draw the line. If you want you can now go over the floor at different points to see how far out the floor really is

Once the floor is lifted and the sistering joists are ready to install (i.e cut to length) you start the installation by first re-setting the laser to the datum line. Always start by installing the joists furthest away from the laser and working backwards towards the laser. Each joist is installed the same way: drop into place (gently!) and fix one end lightly with a single screw at one end only at the approximately correct height, say 10mm above the joist. Then using that first screw as a pivot swing the other end up with the rod held above it until the laser line hits the upper marked line on the rod and screw that end in place lightly. Go back to the first end and check that with the rod using the waggle back and forth technique to find the lowest point. Adjust the position of the joist if required. Then go back to the first end and repeat, only this time fix it properly when it is bob on. Work back down the joist screwing the sister to it as you go until all the screws are tight. I'd recommend pre-drilling the sister and loading it with partly driven screws (driven about 35 to 40mm in at something like 200 to 300mm centres) before installation and using a 5 x 80


Until the floor is opened up there is no way to tell. The walls which run in the same direction as the floor boards will be OK as they run across the joists - it's the ones running at right angles to the floorboards where there may be issues. Incidentally I did touch on that in post #22 and how to deal with it.

If the floor wasn't too far out I'd probably also go with a 4mm layer of plywood (150mm screw centres) and screed as well, despite the potential faffing about with the edges, but then I've not seen the job in person, and that is merely conjecture on my part
Concise advice. Thanks.

Will pass that on.
 
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Until the floor is opened up there is no way to tell. The walls which run in the same direction as the floor boards will be OK as they run across the joists - it's the ones running at right angles to the floorboards where there may be issues. Incidentally I did touch on that in post #22 and how to deal with it.
As I've said throughout, (... and this is another Victorian South Wales terrace with the same layout as mine :) ) - I bet my bottom dollar that the landing floorboards run under the wall with a joist on the line of the 'cuts' and another joist just the other side of the wall!
Whether the weight of the wall supported by those cut floorboards has caused the deflection of those two joists is another question. My boards are staggered, so there are some long and short boards going all the way into the next room.
I am happy to be proved wrong, but I would just warn the OP that this is how my house works and this might be what to expect! ;)

...oh, and OP, please keep us updated on how your mate gets on!
I would love to know if I've made a fool of myself! ;)
 
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As I've said throughout, (... and this is another Victorian South Wales terrace with the same layout as mine :) ) - I bet my bottom dollar that the landing floorboards run under the wall with a joist on the line of the 'cuts' and another joist just the other side of the wall!
Whether the weight of the wall supported by those cut floorboards has caused the deflection of those two joists is another question. My boards are staggered, so there are some long and short boards going all the way into the next room.
I am happy to be proved wrong, but I would just warn the OP that this is how my house works and this might be what to expect! ;)

...oh, and OP, please keep us updated on how your mate gets on!
I would love to know if I've made a fool of myself! ;)

Will do.

I know that the surveyor told him that the wall is a stud wall. Would the old wall have been brick? Lath & plaster?

He may have to level the floor by putting ply down if the floorboards are indeed directly under that wall?
 
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I know that the surveyor told him that the wall is a stud wall. Would the old wall have been brick? Lath & plaster?
For mine, lath and plaster, with brick between front and rear bedrooms.
He may have to level the floor by putting ply down if the floorboards are indeed directly under that wall?
As J&K has suggested in #22, there are ways around it, but just getting the boards out from beneath the wall may become a hassle.

Well anyway, here's hoping I'm wrong! :)
 
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For mine, lath and plaster, with brick between front and rear bedrooms.

As J&K has suggested in #22, there are ways around it, but just getting the boards out from beneath the wall may become a hassle.

Well anyway, here's hoping I'm wrong! :)

I meant, by taking skirting off and laying ply down and shimming and then replacing skirting (and cutting door frame etc).
 
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I bet my bottom dollar that the landing floorboards run under the wall with a joist on the line of the 'cuts' and another joist just the other side of the wall!
Some do, some don't. there is a great deal of variation I've found

Whether the weight of the wall supported by those cut floorboards has caused the deflection of those two joists is another question.
I somehow doubt it unless the joists are very undersize, The floor boards would ensure that the weight of the wall is spread across a number of joists unless they were all cut at more or less the same pointy, near to the wall

One thing that is for certain. though - getting extra supports in beneath a wall like this is hard work and a common job to undertake on terraced houses, especially when re-locating walls
 
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The floor boards would ensure that the weight of the wall is spread across a number of joists unless they were all cut at more or less the same pointy, near to the wall
That's my point, unlike my house where the boards are staggered across the floor, this house has short boards across the landing, with all the 'cuts' in the same place:
Screenshot_20220828-100149_Chrome.jpg
Screenshot_20220828-100245_Chrome.jpg


I suspect the weight of the wall is only taken by two full joists and whatever magic supports the half landing outside the bathroom! :)
 
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That's my point, unlike my house where the boards are staggered across the floor, this house has short boards across the landing, with all the 'cuts' in the same place:
View attachment 277923 View attachment 277924

I suspect the weight of the wall is only taken by two full joists and whatever magic supports the half landing outside the bathroom! :)

Why would they have cut the floorboards like that? Or were they laid like that originally?

I guess the weight is not a lot if it is indeed a stud wall.
 
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I went to look at the house with my mate. Floor def leaning. Like being on a ship! Lol.

Looks as if the boards from the landing go under the wall and into the bedroom. No idea why the boards have been cut like that in bedroom unless thats original! (See pic in post 1).

The floor slopes a little in the bedroom towards that same wall.

To me, i think he needs to put something 'onto' the floorboards to level them out (after taking skirting off etc).

Otherwise it means cutting the floorboards up against the wall either side and sistering joists? Too much hassle maybe?
 
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Looks as if the boards from the landing go under the wall and into the bedroom. No idea why the boards have been cut like that in bedroom unless thats original!
Boards are original, not cut, it's just they used full length boards in the bedroom, and the gap that was left was filled in over to the landing.
I guess the weight is not a lot if it is indeed a stud wall.
The weight of the stud wall should be nothing to worry about :)
To me, i think he needs to put something 'onto' the floorboards to level them out (after taking skirting off etc).
Yes.
 
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My mate has had the full report of the survey on the house back. These are the points brought up. What you think?

Points on survey:


  • Window brick arch lintel may need cementing
  • Rear extension lacking exterior paint
  • Wall vents check for blockage
  • Damp by front door (wooden door and frame) picked up by 'meter'
  • Attic hatch wood soft in places
  • large holes in attic wall needs filling
  • Blown plaster on some internal walls?
  • Slight bowing laminate floor in living room? (Looks new though)
  • Sloping upstairs floors
  • Inner doors adjusted so that they close
  • No handle on bathroom door
  • No smoke / carbon alarms
  • Drain cover broken in rear garden
  • Japanese knotweed in garden (5 year plan in place

Sloping floors are his big concern plus soft wood in places by attic door.

Laminate in living room looks new he said...
 
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