Plaster Problem...

[Matt Durkin]

Hi All, I have just stripped the wallpaper from my dining room and have discovered some problems with the plasterwork. My house is a victorian house and the problem wall has a chimney breast and has also been damp proofed. The damp proofing area is fine (and not damp), the plaster is strong and smooth, but my problems are mostly with the chimney breast and the old plaster above the damp course. The old plaster seems to be a browny colour (as opposed to the pink of the newer stuff over the damp course), and seems very soft and crumbly. When removing a couple of screws from the wall, big holes formed. I can tell that the plaster is not well attached - it crumbles away quite easily, and I suspect quite large sections could be easily removed.

So, what should I do? Fill the holes, and then skim the wall, or pull off all the loose plaster and replaster the wall? How much would I expect to pay a plasterer to patch this up and skim? The wall is about

3 metres by 2 metres (up to the picture rail which I'm not currently planning to remove - or would I need to remove this?). Any advice very much appreciated.

Secondly, under the wallpaper on the outside wall was a thin layer of polystyrene. Would this have been attached to the wallpaper originally? What is it for? Insulation maybe, or is it related to the damp course?

Thanks Matthew

[John Smith]

I can't help with the plaster questions but the polystyrene could well be what was fashionable back in the 60s and 70s on older houses where the walls, even the plaster, was pretty rough and uneven. You could buy polystyrene 'wallpaper' which you put on the walls first to give an even surface over which to place 'proper' wallpaper.

John.

[Andrew Gabriel]

This sounds like new plaster which has been damp for a long time. Where is it located, on the chimney breast? Is the fireplace closed up, and if so, is it ventilated bottom and top of the flue?

You need to work out why it's damp and fix that, and then pull it off, let it dry if it's soaking wet and replaster.

I would guess that scratch and finish coat will take it over half a day's work (and I doubt you'll get a plasterer to turn up for just half a day anyway). If you're paying for a day's work, then you might want to search out any other bits of reskimming you want doing. Price depends on location, but you are probably looking at £200/day plus materials (which don't cost much).

[John Smith]

Do plasterers make about 50K a year then?

[Matt Durkin]

The new (pink) plaster is very solid and doesn't feel damp or cold. The fireplace isn't closed up, it has an old wrought iron fireplace. We don't ever use the fire though = I suspect I'd have to have the chimney swept. I'm guessing the fire will have been used extensively during the life of the plaster. Most of the loose plaster is on the front of the chimney breast above the fire.

The old plaster isn't damp - or at least when it crumbles away it is very dry and the brickwork behind is not wet in any way. I think the plaster is just very old! I have been reading a few other threads about victorian houses and it seems this is quite common. The plaster in my lounge above the radiator was just the same - I guess the heat dries out the plaster and it looses cohesion with the wall. From what people have said on other threads (about trying to fix anything to these victorian plastered walls), I think it's normal to patch up the holes and skim. What do you think?

This is good news. I was expecting it might be much more. If I can get a plasterer in for 200 quid, I'll probably do that. I'll pull of anything loose and then he can apply new. This way it will make it a nice day's job and I'll have nice smooth walls at the end of it. Would I need to remove the skirting boards and picture rails or could he plaster the section inbetween. Both have been there a long time and might be a challenge to remove...

Thanks for the advice!

[Hywel]

Only if they work 5 days a week for 50 weeks.

[Andrew Gabriel]

Most of them won't touch half or one day jobs at all IME. For a longer job, I would expect the price to be lower. Take home pay != labour price charged for work.

[N. Thornton]

more like 100+ materials - and let the plasterer tell you where to get the plaster and what kind. There are always folks you can get in for nearer 40 a day... Why not diy?

Regards, NT

[Matt Durkin]

Thanks! I may yet DIY, but at the moment I'm just a little concerned about pulling the plaster and the whole wall coming down. I'm not sure I'd be able to do a whole wall - the biggest area I've plastered was about 3'x1' after I had to rebuild the wall under my bay window (long story - removed window to get sofa in and wall came away with windowsill. uPVC guys had literally glued the sill to the bricks and the glue was stronger than the 100 year old cement!)

Anyway - I digress! If I am going to DIY, what kind of plaster do I need to apply straight to the brick face (this is now visible in a few small places and if I continue will be what I am plastering to mostly)? I used wicks multi-purpose stuff last time but that would be pricey for a large area. Will the plaster just stick to the brick, or will I need something else there for it to stick to?

Thanks Matthew

[Andrew Gabriel]

If you can avoid taking the plaster off the corners of the chimney breast, it will make replastering the frount much easier. Obviously, you can't avoid it if that plaster is damaged too, but if it's OK, then don't get too carried away with the plaster removal. When you remove a piece of plaster, the next bit will always have come away from the wall slightly -- if you don't stop somewhere, you will end up stripping the whole room.

I use bonding coat for the scratch coat if the wall's dry, and multifinish for the finish coat.

You paint the brick with diluted PVA glue before plastering. You will probably need to do two coats unless your chimney breast is built with engineering bricks (most unlikely;-). Get plenty of PVA solution into the edge of the ajoining plaster too, and down any tiny crack where it may have come away from the wall when the neighbouring piece was removed. Ideally, you start plastering just before the last PVA coat has completely dried.

[N. Thornton]

Common method: 1:1:6 render onto the brickwork, and just the last 3 mm is plaster. I'm sure there are other ways to do it too!

Regards, NT

[John Smith]

Don't you need a long piece of wood as a straight edge to use at the end to smooth things out?

[Andrew Gabriel]

Yes, to create a flat scratch coat. You use the trowel to smooth out the finish coat though.

[John Smith]

Ah, thanks for that. I always thought that the wood was used to level the final surface. Has anyone used these seemingly extra big flat trowels for plastering sold in places like B&Q? Are they ideal or too big?

J.

[John Smith]

Excuse my dummies question... but what is render? Isn't that plaster?

J.

[Andrew Gabriel]

I don't know the strict definition. My guess would be that _render_ covers any type of solid surface finishing applied after a wall is built (maybe including plaster), but _plaster_ is limited to a surface finished with plaster.

[N. Thornton]

no, its cement mortar, 1 part by volume cement, 1 part lime and 6 parts sand. But as youve seen, there are various ways to do it.

Regards, NT

[The Natural Philosopher]

It is, and as often used as such, but it takes longer to go off and is more expensive.

'loaded' plaster - bonding plaster - is more often used.

[Andrew Gabriel]

You need to wait at least 24 hours before you can apply finish coat plaster to sand and cement scratch coat. Mixing up sand and cement (and lime if you like it) is also much more work than mixing up plaster (it's heavy, and you'll need a cement mixer for any reasonable wall area to be covered -- I do it with a shovel in a wheelbarrow, but that's not recommended unless you are built like Arnie, which I'm not). For these reasons, it isn't preferred unless you are looking for some particular property property of it, such as working on damp walls. Also, a harder scratch coat is not necessarily a good thing.

[John Smith]

That to me, as a newbie to all this, would make sense as it would seem to be more solid as an 'undercoat' to a finished plaster than using plaster for both undercoat and finish.

John.