Loft floor lifting

[DumbBlonde5]

The builders have finished our loft and we have since painted and are just getting quotes for fitted furniture. Near the end of the build we noticed the tongue and groove chipboard/ply floor made a huge bang near our front dormer window. It was like a gun being fired and only happened when you stood on it. The builder said it needed another screw and we thought it was sorted.

Fast forward a few months and we heard a huge bang one evening. Nobody was in the loft. Nothing to see but the next day I walked on the floor and the same area has lifted and is banging again. The floor generally creaks but the builder said that's normal until carpet is laid.

Where this bang is we intend to put a window seat with storage. There will be no carpet underneath. Should we try and fix the floor again first or leave it and just hope the new window seat stops the noise? If we fix it what is the best method?

 

[JohnD]

I have a feeling the floor will be chipboard and has some unsupported joints.

Was it fixed down with nails or with screws?

Do you know if the T&G joints were glued?

Carpet will not cure it.

But any delay will give the builder time to get away.

When adding extra screws after the floor has been laid, there is more risk of going through a pipe or cable, unless the positions were durably marked on the boards.

I don't know a good cure, other than cutting out the faults and laying additional supportive struts before screwing in a new piece.

If your contract specified the floor construction you may have a claim if the work was not done to specification. Was the floor design drawn up and approved to Building Regulations? Do you have an architect or other help?

 

[big-all]

i would get a long strait edge up there and see if its a dip or lump
a new floor should be flat so its either dipping and holding down when you stand on it
or raised and dropping when you stand on it
with a zigzag joint on the boards the movement has to be on 2 surfaces butted up against each other as zigzag will only drop say half a millimetre and is unlikely to do more than creak

 

[tell80]

You mention T&G ply and chipboard - are they both the same metric thickness, say 18mm or 22mm?
The bang could be coming from expansion - if no expansion gaps have been left at abutments.
Are there heating pipes below the floor?
Creaking floors are not "normal".

 

[Deleted member 174758]

...The builder said it needed another screw and we thought it was sorted...

...the next day I walked on the floor and the same area has lifted and is banging again. The floor generally creaks but the builder said that's normal until carpet is laid...

Basically, your builder is talking complete and utter tosh! When a T&G chipboard floor is properly installed it is always supported by a joist, solid strutting or a "noggin" beneath the end joints (a few sub-floor manufacturers allow a 100mm unsupported joint, but they also specify glueing to the joists), it should always be screwed down (NEVER nailed) and there should be sufficient screws of the correct type, it is always adequately glued at the T&G joints, it is always glued down onto the tops of the joists and there is always a 10mm or so gap at the edges to the walls and there should always be adequate clearance between fixed services (e.g soil pipes, extraction ductwork, water pipes, etc) and joists/sub-flooring to avoid problems. If it's creaking and banging now it won't ever get better when you carpet it - in fact it will probably just get worse over time!

From his response it seems your builder is either lazy or clueless. He needs to put an an experienced chippie in to sort it out (not an apprentice or a labourer with a cordless screwdriver)

Creaking might be caused by the edge of a board abutting the wall, it might be a pipe or duct being rubbed against a joist (like it or not joists aren't rigid, they do flex slightly when you walk across them - that is necessary) or you might have an issue with joists not being properly secured or even wall sole plates not being properly nailed down because a nail has blown out or even missed a joist, etc. Sudden cracks and bangs are often related issues with a bit more movement, I've found.

In terms of fixing it, it is necessary to identify where the noises are coming from. If it is the edge of the floor that often means the skirting has to come off to deal with inadequate gapping. In the middle of a floor I'd start by adding more screws (bearing in mind the comments made by @JohnD above about potentially hitting services), but if that doesn't work it's probably going to be a case of lifting a section of floor to find the cause, correcting it, then replacing/renewing that section of floor

 

[DumbBlonde5]

Thank you for all the replies. The floor has not been glued and the builders made various mistakes that meant sections of the boards had to be cut and taken up. They were all nailed/screwed down. I suspect nails as the builders LOVE nail guns and at the end we were sweeping so many nails up it was ridiculous. They nail gunned all the door frames etc.

The board in question is near the edge of the wall. It's also where the plumber put pipes for a radiator we didn't want (as we always planned to put a window seat there) and so we asked him to remove the pipes. I'm not sure how much pipework he still left under the floor but the huge bang came after we put the heating on so it's possible it's expansion.

No markings on floorings.

I will go and look for a lump or dip but I suspect it's raised as it bangs when we stand on it but then is silent until it has risen again.

If I speak to the builder he will just get them to nail gun it more and out architect is no help. Building control passed the loft even after I mentioned some of my concerns.

 

[Deleted member 174758]

The floor has not been glued and the builders made various mistakes that meant sections of the boards had to be cut and taken up. They were all nailed/screwed down. I suspect nails as the builders LOVE nail guns and at the end we were sweeping so many nails up it was ridiculous. They nail gunned all the door frames etc.

I'm a time served joiner, and I love my nail guns too (plural), but I also know when it's appropiate to use them. Your builder, however, sounds like an idiot, as are the guys he employs.

I will go and look for a lump or dip but I suspect it's raised as it bangs when we stand on it but then is silent until it has risen again.

If they have nailed down the floor and not glued it this will keep happening. That's why flooring manufacturers state that T&G chipboard should be glued at the joints and to the joists. It is actually fairly normal to have the odd joist which isn't completely flat - those you always install crown uppermost, the theory being that when the floor is in use the load it is carrying will flatten it out, but the limit of crowning is only about 4mm, no more. In fact when I'm installing floor I aim for discrepancies of no more than about 2mm across the entire floor - and if needs be I'll power plane a couple of millimetres off the top of a joist to acheive it, but it is rarely necessary with timber which has been properly stored on site. Nailing has the disadvantage that it the joists aren't flat you can get movement of the sub-floor - screws on the other hand are far less prone to coming loose if installed properly with the boards glued to the tops of the joists

If I speak to the builder he will just get them to nail gun it more and out architect is no help. Building control passed the loft even after I mentioned some of my concerns.

Building control won't comment on the way the floor is fixed down, I'm afraid.

 

[The Samaritan]

Did you get building control to oversee the job the reason I ask is at times the joists need additional support.

Unless you ID the creaks/noise it will only get worse and cost you more time and money to put it right.

So research now and a solid fix may seem the longer way around this now but longer term a pice of mind and less costs.

 

[Deleted member 174758]

Did you get building control to oversee the job the reason I ask is at times the joists need additional support.

"Extra support"? Just what does that mean, exactly? Even if the joisting is somewhat undersized or at too wide centres (both things the BCO will often pick up on) you still won't get creaking of the sub-floor if it is correctly fixed (i.e. glued and screwed)

 

[The Samaritan]

"Extra support"? Just what does that mean, exactly? Even if the joisting is somewhat undersized or at too wide centres (both things the BCO will often pick up on) you still won't get creaking of the sub-floor if it is correctly fixed (i.e. glued and screwed)

Two separate points pal. As you know one was a general heads up and the other was adressing the question.
https://claphamconstructionservice.com/blog/loft-conversion-floor-joist-regulations/

Thanks

 

[Deleted member 174758]

You still didn't answer the question, what extra support would be required and how would you install it? It's a simple enough question if you understand floors

 

[catlad]

Sorry to here your problems Blonde but it would seem you have employed a moron.