plasterboard disintegrated behind tile

[crafty]

Hi, today i was re-grouting the tiles in my shower. As i was scraping out the dirty grout, one of the half tiles immediately above the shower tray came out, and, to my horror all the plasterboard behind was soaking wet and had disintegrated. I discovered a leak and have repaired it, BUT, how do i re fix the tile that came out with nothing to fix it to? any help appreciated. Thanks Crafty.

p.s. i suppose the adjacent tiles may just be clinging to each other, eek.

[Rich]

Hey Crafty

I'm afraid there truly is only 1 thing you can do here, if you want to avoid more problems later, and thats to pull off any surrounding tiles that are lose enough to come off in your hand.

Given that you now have a hole in the wall, you should be able to feel the condition of the plasterboard behind the tiles, but its highly likely that moisture from the leak will have weakened any surrounding tiles, so its would be wise to take of at least 1 tile surrounding the hole.

If the plasterboard around this hole is sound and as new, then you can screw in place a few battens behind the hole, putting screws through the surrounding platerboard each side of the hole (Hence why you take off the tiles) which then leaves you with several battens going across the back of the hole, for you to fix a new peice of plasterboard to.

Once trick here is, do NOT cut an exact fitting peice of plasterboard....

What you do is, cut out a peice of plasterboard that is at least 10cm bigger than the hole, all the way round, then measure out your exact fitting peice in the middle, and ONLY score the plasterboard enough to snap it in 1 direction, leaving the side that you will stick the tiles to, attached to the centre peice of board.

So lets say your hole is 20 wide by 20cm high, you cut a peice of plasterboard 40cm x 40cm whcih gives you 10cm all the way round, and you can then score out your 20cm x 20cm section in the middle, and once you break/snap the plasterboard on the back of it, remove the actual plaster from the 10cm edges, all the way round so you have a perfect fitting 20cm x 20cm peice, with 10cm of paper attached to it all the way round.

Now, when you screw on this peice of plasterboard, you can use plasterboard joint filler all round the edge of the hole, and spread it out 10cm around the edge of the hole, and when you then screw in your newly made repair peice, work from the centre outwards to stick the paper edges down onto the surrounding filler to provide a good strong seal that overlaps all the surrounding board by 10cm.

Feel free to make the edges as big as you like, but I wouldnt do less than 10cm/100mm

I found this to be a common way to repair holes in walls when i lived in Florida as all their places are made from wood and "drywall", its quick to do and gives a strong finish. You might then want to cover all exposed area's with a good quality tile adhesive, just a thin film of it all over the entire lot, then do your normal tile adhesive application before re-applying your fallen tile.

[crafty]

Hello DIY GUY, Thank you so much for your very comprehensive and helpful reply. I will give it a go today. Best Regards, Crafty.

[verne]

the simple answer is - you can't!

as far as i know there are no products that bond tiles to fresh air.

i suggest you carry on removing the grout and any tiles not securely fixed until you have discovered the extent of the problem - then attempt to remove a few more tiles so you have an area of good solid plasterboard around the hole that it will be necessary to make by removing the sodden plasterboard.

give it some drying time so your repair is not going to trap any moisture where it can cause long term damage.

clean the edges of the resulting hole. don't worry if the hole isn't a regular shape - plasterboard repairs are more successful with irregular shapes as it provides more bonding area around the edge...

if it is a stud wall with a cavity behind it you will need to provide a shoulder to prevent the patch from falling through the hole. you can do this by bonding some bits of board to the back of the existing plasterboard at convenient intervals around the hole leaving an inch or so protruding into the hole area...

if it is a battened wall you can use the same method or provide extra battens or use a combination of the two methods.

cut a patch to fit the hole from some board of the same thickness, but slightly smaller to leave a 3 or 4mm gap all around for the no-nails adhesive. glue (pva or similar) the patch into place against the shoulder and using spacers around the edge to maintain the gap until the glue is holding and then insert a bead of no-nails around the edge...

if your plasterboard is just a dot and dab cladding over a solid wall it will be straightforward to provide a few dabs of adhesive and settle the patch until it provides a flush surface.

the hard bit of the job will be removing the old tile adhesive without breaking any...

[crafty]

Thanks very much Verne. Very helpful, I will start investigations and repairs tomorrow.

Best Regards and thanks. Crafty.

[tiles2u]

Here are a couple of points to help - further to what has already been said.

1.) To get old tile adhesive off the back of tiles that you wish to reuse, then soak them for 2-3 days totally submerged in water. This leads to the second point.

2.) Make sure that any bathroom is well ventilated, as if moisture has no where to go then it will travel through the grout lines. When buying grout and adhesive people make the mistake of buying "water resistant products" rather than "water proof". 90% of grouts and adhesives are water resistant - what this essentially means is that water won't damage or breakdown the grout but will travel through it!!! Thus as in this case can damage the sub surface... the other option of course is to use a tanking kit for the parts of the bathroom that are subject to a lot of water impact such as in a shower.