I live in 1980s house that had a single story extension built a couple of years ago. This involved removal of a section of supporting wall at the rear of the property and replacement with a pair of RSJs (bolted) to support the first floor wall, parts of the roof structure, and floor joists for the bedrooms. The span is about 4m.
Following the installation, it became apparent that the floor joists had dropped from their original positions, to varying degrees, but generally getting worse from one end of the RSJ to the other. This averages about 10mm, but is 15+ at the worst point. Initially, this manifested itself as a visible gap between the skirting board and floor (chipboard) and some minor localised creaking upstairs. Over time, this has slowly but surely got worse and worse, to the point where taking a step practically anywhere on the first floor causes a creak of some sort. I’m using ‘creak’ as a general term for creaks, squeaks, clicks, cracks, clonks and thuds.
If I put my head on the floor upstairs and shine a torch into the gap, I can clearly see that joists have dropped, but the blockwork has not (at least, not by as much – and not significantly). In other words, I can see where the joist end extends beneath the skirting board and there is a visible gap above it, with a rectangular gap in the mortar around the top of the joist where it would have originally sat. I’m assuming that the widespread creaking effect is due to the interlocking nature of the boards and the fact that the other end of the floor joists cross an internal load-bearing wall and form the upstairs landing. In other words, the joists have see-sawed on the internal wall, so the ends beneath the landing have risen, albeit only slightly.
I paid an SE to assess the situation recently and he felt it unlikely that any significant further movement would occur, but acknowledged that what I’m seeing is the result of poor workmanship by the builder and is not normal. He suggested that it might be possible to jack the joists back up into their original positions and pack them appropriately. It might be that the blockwork isn’t packed properly either, but has somehow hung in position – perhaps through a combination of being held up by their neighbours and perhaps even by the drylining plasterboard stuck to the inner surface. I think the blocks are ‘thermalite’ type, so are lightweight and of a chalky/crumbly consistency. By the way, I had no knowledge of house construction until this problem started, so excuse me if I’m using the wrong language or have misunderstood anything.
I’m guessing that the problem stems from poor packing of the RSJ ends during installation. I remember a single prop remaining under each end of the RSJs for a couple of days following installation and suspect that there was some downward movement when they were removed. I only had the opportunity to inspect the work each evening during the build and had no reason to be suspicious at that point. Beyond some hairline cracks to the plaster around the ends, I don’t think there has been any further movement in the RSJs since.
An alternative to jacking the joists up might be to simply screw down the floorboards upstairs to reduce movement. However, I’ve done this in one area and it hasn’t worked. As long as the joists remain out of alignment, I don’t think the boards are going to sit happily on them, no matter how many screws I use to force them into an unnatural position.
So, what I’m hoping you guys can do is look at what I’m thinking of doing and tell me whether you think it’s sensible. Here’s the potential plan:
- Remove a section of ceiling downstairs, along the full length of the RSJ. This will give me easy visibility of the RSJ itself, the joists and blockwork, clearing up any mystery around what’s actually going on in there.
- Fit an Acrow under each joist individually. I’m assuming this will give me more control than using a scaffolding plank and fewer props.
- VERY carefully attempt to jack the joists back to their original positions (or, if the blockwork turns out to have dropped at all, then as far as I can without starting to jack the wall itself up).
- Insert some form of packing under the joist ends. I need some advice on this, but the SE mentioned packing with slate.
- If necessary, also pack beneath the blockwork and potentially patch up any cracks in it and around the joist ends (small fragments of broken block had collected in the gap under the skirting, although it’s not entirely clear where this has come from). I also need advice on how to do this, particularly the materials required.
- Make good the ceiling.
- Screw down the floorboards upstairs into what should now be an even joist arrangement. I’m under no illusion that the structure will be exactly as it started, so I’m assuming that screwing-down will be necessary to return some rigidity to the structure.
If it proves appropriate to get a builder to actually do this work for me, then I’ll do it. But, in the meantime, I’m hoping it might be something I can do myself with appropriate planning, advice and a friend or two to help.
Thanks in advance for any advice you can offer.
- Craig.
Following the installation, it became apparent that the floor joists had dropped from their original positions, to varying degrees, but generally getting worse from one end of the RSJ to the other. This averages about 10mm, but is 15+ at the worst point. Initially, this manifested itself as a visible gap between the skirting board and floor (chipboard) and some minor localised creaking upstairs. Over time, this has slowly but surely got worse and worse, to the point where taking a step practically anywhere on the first floor causes a creak of some sort. I’m using ‘creak’ as a general term for creaks, squeaks, clicks, cracks, clonks and thuds.
If I put my head on the floor upstairs and shine a torch into the gap, I can clearly see that joists have dropped, but the blockwork has not (at least, not by as much – and not significantly). In other words, I can see where the joist end extends beneath the skirting board and there is a visible gap above it, with a rectangular gap in the mortar around the top of the joist where it would have originally sat. I’m assuming that the widespread creaking effect is due to the interlocking nature of the boards and the fact that the other end of the floor joists cross an internal load-bearing wall and form the upstairs landing. In other words, the joists have see-sawed on the internal wall, so the ends beneath the landing have risen, albeit only slightly.
I paid an SE to assess the situation recently and he felt it unlikely that any significant further movement would occur, but acknowledged that what I’m seeing is the result of poor workmanship by the builder and is not normal. He suggested that it might be possible to jack the joists back up into their original positions and pack them appropriately. It might be that the blockwork isn’t packed properly either, but has somehow hung in position – perhaps through a combination of being held up by their neighbours and perhaps even by the drylining plasterboard stuck to the inner surface. I think the blocks are ‘thermalite’ type, so are lightweight and of a chalky/crumbly consistency. By the way, I had no knowledge of house construction until this problem started, so excuse me if I’m using the wrong language or have misunderstood anything.
I’m guessing that the problem stems from poor packing of the RSJ ends during installation. I remember a single prop remaining under each end of the RSJs for a couple of days following installation and suspect that there was some downward movement when they were removed. I only had the opportunity to inspect the work each evening during the build and had no reason to be suspicious at that point. Beyond some hairline cracks to the plaster around the ends, I don’t think there has been any further movement in the RSJs since.
An alternative to jacking the joists up might be to simply screw down the floorboards upstairs to reduce movement. However, I’ve done this in one area and it hasn’t worked. As long as the joists remain out of alignment, I don’t think the boards are going to sit happily on them, no matter how many screws I use to force them into an unnatural position.
So, what I’m hoping you guys can do is look at what I’m thinking of doing and tell me whether you think it’s sensible. Here’s the potential plan:
- Remove a section of ceiling downstairs, along the full length of the RSJ. This will give me easy visibility of the RSJ itself, the joists and blockwork, clearing up any mystery around what’s actually going on in there.
- Fit an Acrow under each joist individually. I’m assuming this will give me more control than using a scaffolding plank and fewer props.
- VERY carefully attempt to jack the joists back to their original positions (or, if the blockwork turns out to have dropped at all, then as far as I can without starting to jack the wall itself up).
- Insert some form of packing under the joist ends. I need some advice on this, but the SE mentioned packing with slate.
- If necessary, also pack beneath the blockwork and potentially patch up any cracks in it and around the joist ends (small fragments of broken block had collected in the gap under the skirting, although it’s not entirely clear where this has come from). I also need advice on how to do this, particularly the materials required.
- Make good the ceiling.
- Screw down the floorboards upstairs into what should now be an even joist arrangement. I’m under no illusion that the structure will be exactly as it started, so I’m assuming that screwing-down will be necessary to return some rigidity to the structure.
If it proves appropriate to get a builder to actually do this work for me, then I’ll do it. But, in the meantime, I’m hoping it might be something I can do myself with appropriate planning, advice and a friend or two to help.
Thanks in advance for any advice you can offer.
- Craig.
