Plaster Skimming Nightmare

[hairyfish]

Your wisdom would be much appreciated on our skimming nightmare – sorry for the length of the posting!!!

We recently purchased a 1930’s house and painstakingly stripped off all the wall paper (no steamers), the original walls (lime plaster – it think) had ‘crazing’ lines all over but were generally ok apart from the a few larger cracks here and there. As we had to remove all the old lath and plaster ceilings, we decided to have all the walls skimmed as well.

The original walls throughout the house had lots of dust, wallpaper glue and old paint residue (some of which was powdery – we’ve now been told this may be distemper?), and we raised our concern with the builder at the time but he assured us that applying pva to the walls would provide all the grip required for the new plaster skim, and his plasterer did in fact roll on a watered down pva solution onto the walls and let this dry before then starting to apply the skim.

Unfortunately however the new skim has started to blow away from the walls, in one of the bedrooms this is clearly down to the powdery stuff on the walls (the plaster simply hasn’t bonded to the wall at all - when you rub the wall behind where the plaster has fallen down, your hand is covered in powder), and in the wc where the walls had in the past been painted with gloss, the pva/plaster again has simply not bonded to the wall at all.

Having subsequently gone through the house knocking on the walls, we have found that there are hollow sounding areas in all the rooms and cracks are visible in these same and other areas – the plaster doesn’t seem to be detaching from the walls in quite the same way as yet, but is this just a question of time as we go through the warm and cold seasons?

One other possible problem is that we know that in some areas, including external walls, he has used bonding plaster to fill larger holes (for example where windows have been blocked up)…is it true that this can lead to damp problems?

It’s difficult to know whether the hollow sounding areas are blown areas of the new skim or blown areas on the original plaster? Either way, with hindsight it’s clear he hasn’t prepared the walls appropriately, including where necessary hacking away any blown areas of the original plaster. If only we knew then, what we know now!

We want to avoid wallpapering over as it doesn’t deal with the problem and as of course it becomes an even bigger nightmare to resolve any issues that arise later once we have decorated and bought new carpets, etc? So the question is, what do we do from here?

1) Do we simply hack away the areas that sound hollow (of which there are many per room) right back to the brick and then build these out with bonding/hardwall plaster and then re-skim the whole lot again?

I am concerned that we are inevitably going to miss some hollow areas and that another layer of skim on top of a layer which is probably not properly bonded in the first place is just going to cause more issues. After all throughout the house the walls had the same powdery paint and dusty surfaces and were of course prepared in the same way by the plasterer.

2) Do we have the skim layer he put on completely hacked off, then hack back any blown areas of the original lime plaster back to the brick, build these areas out, and then re-skim the whole lot?

I think this would give us more peace of mind, however, as the original lime plaster is probably very fragile, I am concerned that hacking away the whole lot (although I suspect it would come away fairly easily) may cause areas of the original lime plaster to de-bond from the brick, and then of course we have a whole new set of problems.

3) Do we do something else entirely?

Any help / guidance greatly welcomed!!

Many thanks!

 

[PrenticeBoyofDerry]

By what you have explained, sounds that you could well have a problem that is related back to the original plaster on the wall.
In my opinion I would strip it all back to the brick or studwork and start back from scratch.
Make sure if there are any damp problems in any areas, that they are fixed before you carry out the new plastering work.

 

[hairyfish]

Thanks for the advice!

Why do you think there could be a problem related to the original plaster? This seemed in pretty good condition apart from the crazing and odd crack here and there.

Also, there is no damp currently, but we have been told that as the plasterer has used bonding plaster on external walls, this is likely to draw water in and cause damp problems in the future - is this true?

 

[joe-90]

The builder will tell you that they are your walls and you prepared them so not his problem. To hack the whole lot off back to brick will cost a fortune (up to 10k) so just patch it up and live with it. The more you mess with it the worse it will get. Time for pragmatism.

 

[Richard C]

The original walls throughout the house had lots of dust, wallpaper glue and old paint residue (some of which was powdery – we’ve now been told this may be distemper?),

Wallpaper glue must be removed; if there are any powdery residues on the wall it must be PVA sealed at least 24 hours before plastering before being PVA’d again immediately before skimming; in some cases a bonding primer may be required

his plasterer did in fact roll on a watered down pva solution onto the walls and let this dry before then starting to apply the skim.

Two PVA coats should be applied, the first should be allowed to dry before a second is applied but the plaster must be applied while the second PVA coat is still tacky. If the spread let the PVA dry before skimming that’s a mistake & will give poor skim adhesion.

Unfortunately however the new skim has started to blow away from the walls, in one of the bedrooms this is clearly down to the powdery stuff on the walls (the plaster simply hasn’t bonded to the wall at all - when you rub the wall behind where the plaster has fallen down, your hand is covered in powder), and in the wc

See above.

where the walls had in the past been painted with gloss, the pva/plaster again has simply not bonded to the wall at all.

Gloss has to be correctly prepped by scoring the surface; I use an old bricklaying trowel & a very stiff wire brush, PVA sealed as above & then PVA’d again before plastering. If he just used the standard 2 coat PVA method on gloss paint the plaster skim won’t stick.

Having subsequently gone through the house knocking on the walls, we have found that there are hollow sounding areas in all the rooms and cracks are visible in these same and other areas – the plaster doesn’t seem to be detaching from the walls in quite the same way as yet, but is this just a question of time as we go through the warm and cold seasons?

If it’s just the skim that’s de-laminating then it’s all down to incorrect prep; if the original plaster is blown that’s another story.

One other possible problem is that we know that in some areas, including external walls, he has used bonding plaster to fill larger holes (for example where windows have been blocked up)…is it true that this can lead to damp problems?

Are these external walls solid brick or cavity?

It’s difficult to know whether the hollow sounding areas are blown areas of the new skim or blown areas on the original plaster? Either way, with hindsight it’s clear he hasn’t prepared the walls appropriately, including where necessary hacking away any blown areas of the original plaster. If only we knew then, what we know now!

If it’s just the skim that’s de-laminating then it’s all down to incorrect prep; if the original plaster is blown that’s another story.

We want to avoid wallpapering over as it doesn’t deal with the problem and as of course it becomes an even bigger nightmare to resolve any issues that arise later once we have decorated and bought new carpets, etc?

Think your some way off that yet, IMO you need to get the situation resolved before you start fitting carpets/furnishings etc or, as you say, it could turn into an even bigger nightmare. Regards your options, it’s very difficult to advise exactly where you go from here without seeing it & making an assessment of how bad things are but I would be inclined to agree with PBD in that for a long term solution you may be better off stripping it all & starting again using someone who actually understands plaster & knows what they are doing.

Have you called your builder back & complained? If so what did he have to say?

 

[PrenticeBoyofDerry]

Why do you think there could be a problem related to the original plaster? This seemed in pretty good condition apart from the crazing and odd crack here and there.

I can only offer an opinion, you say they seemed to be in good condition.
I have been to many jobs, where the plaster seemed to be in good nick, but after a little investigation they were found not to be.
I can only make assumption regarding it's age and condition but if you have lime plastered walls they can go back quite a few years and often they have strated to fail, the surface may look fine but often it is the basecoat underneath that has started to dry and crumble.
As joe has said it could be a quite expensive exersice, now replacing it all.
It's option I would consider but if the cost is an issue, you can repair the problem areas. But normally you will find the rest of the plaster will at some stage need sorting out.

 

[NickB_99]

Why do you think there could be a problem related to the original plaster? This seemed in pretty good condition apart from the crazing and odd crack here and there.

I can only offer an opinion, you say they seemed to be in good condition.
I have been to many jobs, where the plaster seemed to be in good nick, but after a little investigation they were found not to be.
I can only make assumption regarding it's age and condition but if you have lime plastered walls they can go back quite a few years and often they have strated to fail, the surface may look fine but often it is the basecoat underneath that has started to dry and crumble.
As joe has said it could be a quite expensive exersice, now replacing it all.
It's option I would consider but if the cost is an issue, you can repair the problem areas. But normally you will find the rest of the plaster will at some stage need sorting out.

It sounds a bit like my place, which is still being renovated.
The plaster seems basically sound, with a few cracks showing, and a bit of localised 'hollowness'.
Then where I've cut back to brick to sort out the bigger cracks, the undercoat plaster has been very crumbly.
To describe better, when you cut in with a stanley knife in removing dodgy areas, the skim is hard & tough to get through initially, but below, it easily cuts through and goes like 'granulated sugar'.
Then the piece for replacement can almost fall out, it has lost adhesion so much.
I've found a few hollow areas, which I've cut out and re-skimmed/patch skimmed where needed.

What I have noted is that when a section has been replaced (and wasn't necessary to cut the whole wall back) the new patch seems to help strengthen up the neighbouring original undercoat plaster.
For the patch I used Bonding (but hardwall or render prob fine also) with metal lath secured over any brick cracks, as advised here
Taped over the joint against the old and did a re-skim etc.
How long it lasts, who knows.
I'm up to 2 yrs on on the ones I started with and no cracks re-appeared so far. No wallpaper (or lining paper), only matt emulsion painted walls.

I guess it comes down to is it a suspect skim, or is it the original undercoat starting to fail....

 

[hairyfish]

Thank you all for your replies; this is the first time I have used a forum and I am encouraged by and grateful of people's good will in replying - nice to know the whole world isn't bad!

Two PVA coats should be applied, the first should be allowed to dry before a second is applied but the plaster must be applied while the second PVA coat is still tacky. If the spread let the PVA dry before skimming that’s a mistake & will give poor skim adhesion.

Unfortunately it was definitely allowed to dry (in some rooms there was probably a couple of weeks gap between the pva going on and the skimming). No second pva coat was applied at all.

Are these external walls solid brick or cavity?

I believe the external walls are cavity, but we had three windows loosely bricked up with some sort of mortar. Bonding plaster was then applied over this internally. On the outside of these windows some cement render was applied to level the surface and this was pebble dashed to match the rest of the outside (which is pretty old pebble dashing from the looks of it ). I’ve been told that bonding plaster on external walls is a bad idea as it draws water in and can then lead to damp problems. Is this true?

If it’s just the skim that’s de-laminating then it’s all down to incorrect prep; if the original plaster is blown that’s another story.

I think there is probably an element of both; the prep appears to have been totally inadequate, as it has already lead to the skim delaminating in areas, and as I say - I fear the same will continue to happen elsewhere as we go through hot and cold seasons. In your experience, in cases such as this where the bond between the skim and the original wall is under question - if it hasn’t gone within a few weeks is it generally ok, or is it more down to natural movement, expansion/contraction, door slamming, ect?

That said, with hindsight I wouldn’t be surprised if there are areas of the original plaster which are blown. But I assume the plasterer would / should have noticed these in preparing and then skimming the walls. Surely he should then have highlighted the issue to me, to at least give me the option of having any such areas hacked out before then skimming the whole lot. We have spent literally tens of thousands with this builder in renovating the whole property, a few more hundred would not have mattered particularly.

I’m thinking I should have a go at scrapping off a bit of the skim (just with a wallpaper scrapper) in a few of the walls throughout the house to see how well bonded it is and to help me decide whether I need to hack off the skim or if I can simply re-skim over it (once the blown areas are dealt with). Can anyone give me an idea of how well bonded it should be (should I have to struggle to get it off) or does skimming usually come off easily (even when properly prepared and applied)?

 

[Richard C]

Unfortunately it was definitely allowed to dry (in some rooms there was probably a couple of weeks gap between the pva going on and the skimming). No second pva coat was applied at all.

Well that’s definitely not good & is probably the reason why the skim hasn’t adhered particularly well.

I’ve been told that bonding plaster on external walls is a bad idea as it draws water in and can then lead to damp problems. Is this true?[/b]

There is no problem with applying Bonding plaster to the inside of external walls providing they are not solid brick (i.e. the walls have a cavity). Solid brick walls tend to have higher moisture content & can be prone to damp & none of the Gypsum base plasters (not just bonding) will tolerate damp so their use is not advisable. This may be what was meant but if you have cavity walls, with the correct preparation, Bonding should not be a problem.

I think there is probably an element of both; the prep appears to have been totally inadequate, as it has already lead to the skim delaminating in areas, and as I say - I fear the same will continue to happen elsewhere as we go through hot and cold seasons.
In your experience, in cases such as this where the bond between the skim and the original wall is under question - if it hasn’t gone within a few weeks is it generally ok, or is it more down to natural movement, expansion/contraction, door slamming, ect?

If the original plaster is in poor condition or the bond of the skim is suspect, it will in all probability continue to deteriorate. This is usually worse between the summer & winter seasons as the plaster absorbs ambient moisture in the summer & dries out again in the winter due to the effects of central heating.

That said, with hindsight I wouldn’t be surprised if there are areas of the original plaster which are blown. But I assume the plasterer would / should have noticed these in preparing and then skimming the walls. Surely he should then have highlighted the issue to me, to at least give me the option of having any such areas hacked out before then skimming the whole lot. We have spent literally tens of thousands with this builder in renovating the whole property, a few more hundred would not have mattered particularly.

You are absolutely right; the plasterer should have assessed the suitability of the original plaster base for skimming & given you the opportunity to have remedial works done. But if he didn’t PVA immediately before skimming & just skimmed over dry PVA, it doesn’t sound like he knows what he’s doing too much anyway. Personally I would have made it absolutely clear if there were problems with the original base & the consequences not doing corrective remedial works. If you builder employed the spread it’s ultimately your builder whose responsible & I think you have good cause for complaint & rectification at his expense.

I’m thinking I should have a go at scrapping off a bit of the skim (just with a wallpaper scrapper) in a few of the walls throughout the house to see how well bonded it is and to help me decide whether I need to hack off the skim or if I can simply re-skim over it (once the blown areas are dealt with).

Given what you’ve said, I fear the chances are its all going to be the same.

Can anyone give me an idea of how well bonded it should be (should I have to struggle to get it off) or does skimming usually come off easily (even when properly prepared and applied)?

The skim shouldn’t come off easily at all; taking a scraper to it is probably too tough a test but you should definitely not be able to pick it off with your finger nail. Stick a 6 inch strip of Gaffa/Selotape over it & pull, if there is paint on the wall, it may pull that off but it should not pull the skim coat off as well.