Filler doesn't seem to stay put in wall.

justaquestion

Hi,


I have posted before about this, but though got good advice at the time which I thank you for just thought I would run it past you again.


Basically its a walk in shower in bathroom where the shower is backing onto hallway in house, just wall separating them.


I noticed some unsightly bumps in plaster near skirting on hallway, removed them and use poly filler, which came away after some time. Took the advice on forum that it might be water from top of shower tray or waste, (so siliconed the tray) that is getting through to the hallway wall, though it doesn't seem damp to the touch.


Any way refilled again where the bumps are with Ronseal big hole filler, and sanded it down a lot to get as level with wall as possible. Just noticed that the fill is getting a bit loose again in a certain places, space filled is about 3mm in depth, by 4inch long 1.4 inch high


Is it possible that such a thin depth 3 or so mm begins to sag after a while because the filler can't get a good enough grip on wall underneath the filler, and if there is any solution such as to put glue on wall before I apply the filler so as to give it a good enough grip.


I have noticed that all the fillers don't fill any way solid like proper plaster does, and even tapping the fill with your fingers gives a hollow boost sound.


Thanks

Browntoa

are you using PVA glue to prepare the wall underneath the filler ??


helps it to bond better

JohnB47

Is it plasterboard on a stud wall that you are trying to patch up? If the wall sounds hollow when tapped it probably is. If so, it may be that you have movement of the area you are patching and the flexing is causing the filler to loosen. Perhaps when someone is having a shower, the tray is pushing against the wall and flexing it. Is it possible to get someone to walk about in the shower while you look carefully at the filler areas to see if it moves? Or maybe its the floorboards on the other side of the wall that are flexing the wall when someone is walking by.


I've never had filler loosen before and if you've now tried two times using different types of filler, I suspect it's not your method that's wrong.


Look for movement would be my idea.

phil24_7

What is the wall like under the filler? If it is old/sleepy lime plaster then it will not bond very well to this. You may need to cut the plaster out, screw some plasterboard or put bonding filler in there before putting a skim of fine filler over the top.

justaquestion

Thanks for replies, no its a concrete block cavity wall, and once I have cleaned all of the old filler off to refill again is seems totally clean underneath.


The areas where the plaster is sound give a totally solid type of sound compared to the filler part. I did sandpaper filler part quite a bit so maybe the friction to and fro does tend to loosen it a bit.


The suggestion to use PVA glue above in one of the posts (Thank you) seems very interesting.
If I have to refill again, would it be a good idea to use it on solid wall underneath to help bond the filler?
many thanks.

forgotmyname

How big is the hole your filling?

Height/width and thickness of filler? Too much in one go and it wont set properly. get something better than filler, something with fibre strands etc to bind it together before adding a thin skim over the top.

Laz123

IMHO 3mm deep is too shallow to hold filler. Can't you deepen it, then bond it and fill with water-resistant filler?

JohnB47

I'm now wondering if the problem is not a damp wall, as previously suggested but that you are applying a shallow layer of filler to a very dry surface.


I would try damping the area with a sponge or wet paintbrush first - I almost always damp down an area that I'm filling, otherwise the surface being filled sucks all the moisture from the filler and causes cracks and lack of adhesion.


I'm not sure pva should be needed (I never use that with filler) but I'm sure it wouldn't be any harm using a weak solution of pva in water prior to filling. The main thing is to have the surface dampened but not running wet. 'Paint' the area, including the edges, with a wet paintbrush and wait a moment or two - you'll see the surface absorb the water and stay slightly dark. Then is the time to apply filler - before it dries again.


Edit: One other thing. I've used a range of fillers over the years and I find the best now are the cheapest - those boxes of powder filler that you mix with water. The big stores each do their own range but they're basically the same stuff - 'plaster of Paris'?. That stuff dries relatively workable - I use a steel rule and scrape the edge over a filled area to gradually make the area flat and perfectly level with the surroundings. Sandpaper would work well too. I never touch the pre-prepared pots of stuff now. They set far too hard and are difficult to cut back to a level surface.