We had 100mm insulated plasterboard put up about 12 years ago in some of our solid brick cottage. Fast forward to today and it appears one of the walls now is not properly affixed (bellied out a bit and visibly moves when I lean on it).
Google suggests this is due to the fact it builder dot/dabbed onto a solid brick wall.
Realistically, can I fix this by retrofitting mechanical anchors? Is that a bodge too far? The wall is circa 3mx2m, 2mish ceiling. If so, what are best for boards this size? I'm capable of repairing any holes with compound, just unsure which of the myriad of anchors will be best.
And yes, I know now that there absolutely should be anchors anyways!
Ta 🙂
Any fixing isn’t going to get any purchase in plasterboard so my thinking would be a long screw with a big washer plugged into the brick and hope it will pull into the insulation enough to straighten it out. If the dot and dab is still fixed to either wall or board will act as accurate packers.
http://hawkeng.co.uk/index.php?route=product/product&product_id=84
http://hawkeng.co.uk/index.php?route=product/category&path=66_89
Typically you could use something like this, its for attaching fibreboard to a wall but it's basically a large washer to spread the load. The downside is you will have to skim it although if you are canny it will probably pull in enough to be a fill job more than skim
There are loads of different makes, so you might find a thinner one more suited.
If you are fixing into a single skin brick wall, it's difficult to see how you can avoid making a cold bridge, so bare that in mind
Personally I would consider having to take out the old boards and replace - if you do decide to do that, make a sharp straight cut a few inches below the ceiling/wall joint. That way you'll avoid having to remake the joint and make good the inevitable ceiling damage. You'll have to tape and skim the join, but it's less hassle
I would try drilling a few holes and squirting this
or something similar.
Wedge a few batons or even a broom against it to hold in place while it sets. Its messy stuff so be careful about it coming back through the holes. It works well and is a preffered way of sticking boards back these days.
I used normal screws that are stone/concrete rated. They need a nicely sized pilot hole but all can be done with the plasterboard in place. Drill a pilot, screw the screw straight in. You need to tighten them carefully to end up sub flush without ripping through the board. Yes, you do end up with a thermal bridge but I've not found that to be significant.
Hmm.
1. Drill pilot hole through plasterboard and into brick.
2. Insert screw and large washer into plug and hammer through until it's in the brick.
3. Carefully tighten screw. With any luck it'll indent the washer just deep enough into the plasterboard that you can use a fine surface filler to hide it. Obviously this carries the risk that it might break the plasterboard, but if you find a bit of board with mortar behind then this minimises the risk.
I do think that short of replacing the whole lot any fix is going to be a bodge of some description.
bighFree Member
I would try drilling a few holes and squirting thisI second this - I’ve used it a few times to put up plasterboard and tile backer board and it grips well. I’d suggest scooshing some water into the holes before the adhesive as damp surfaces aid the curing process
Hello,
sticking plasterboard to an old solid wall is exactly what you should do not mechanically fix through the plasterboard into the wall as this will likely draw any moisture in the wall into the interior of the room.
If the was done 12 years ago I would suggest the wall behind the wall may have a slight damp issue or the inner face of the wall has broken down a little. If it was a stone wall with no plaster or render the finish internally may be coated with distemper or lime wash. This can flake off or fall away over time. If the wall was plastered or rendered it have come lose over time.
Remove the affected area of plasterboard, check for damp and soundness of the wall. Remove any lose material and stick a section of insulated plasterboard back with foam adhesive, not expanding foam, something like Instastick foam.
The builder was correct not to mechanically fix back into an old solid wall.
Hope this helps. Can put more info up if that would help.
Thanks all, really helpful.
I'm going to try foam, but I'll stick a few mechanical fixings in as I understand they're a good idea for fire resilience!
Cheers again, appreciate it.
You have to have mechanical fixings to pass fire regs, you are right about foam over dot/dab (I used Cerecit CT84) much easier and faster to use and also create small airtight areas by crossing the bead of adhesive over so there is no chance of warm moist air getting behind the board.
I used Insofast fixings but the driver isn’t cheap.
Solid walls shouldn’t be insulated with foam backed plasterboard and it is possible there is a damp issue and maybe mould growth behind. Worth taking a look before you try fixing it back up. The insulation will trap any moisture in the wall from interstitial condensation or penetrating damp. Best option is vapour open insulation like woodfibre fully bonded to the wall and lime plastered over and finished with vapour open paint.