Best way to patch up hole in the paster

[DrEvil]

I was removing some built ins in the spare bedroom and parts of the plaster came away (the walls are lining paper over plaster on brick - Victorian house).

On tapping certain bits were quite loose and so i pulled back certain buts. I have now have some small holes in the wall back to brick, couple are 10cm x 10cm on an outside brick wall where there was a thick layer of bonding (I assume). One large one is 50cmx20cm on an internal brick wall which had a thinner layer of bonding.

At the moment i have pulled back the fairly loose stuff (the kind of bits that fall away with a firm push of your thumb or a slight lever using a knife.

For background this area is generally going to dissapear behind newer built ins with only a small area (5cm coming in front of the built ins) so these areas are going to be a lowly visible area once decorated and this is a spare single bedroom so the emphasis on an immaculate finish is low.

First question is that there are still some hollow areas adjacent to these although these are still relatively firmly in place (I'm going to have to lever this off with some more effort) - is it ok to leave this in place? My main reason is that this will start coming into the visible part of the room more.

The second is what is the best way to patch up these sized holes - is it using a bonding layer then plaster finish? I plan to remove one strip of lining paper and paper a new strip btw over the biggest hole (which is partially in view). Just direct paint on the others (which will be out of sight).

Ta for any advice!!

 

[1john]

Stop levering at it, you will strip the whole wall before you know it. My personal preference for this type of repair os to use one coat plaster and rule it off, then give it a light sanding once dry and add two coats of jointing compound, sand again until a desired finish is acheived, if more jointing compound is required then carry on adding and sanding until you are happy, although if you are going to add another strip of lining paper back in you wont need to go to all that. IMO it is hard to patch in with multi finish, there;s a bit of an art to that, one coat is easily sandable once fully dry and the same for jointing compound.

 

[roughcaster]

I agree with what John said about "not" levering off plaster. If you do have to remove any limited areas of plaster, cut around it deeply first, with a stanley knife,, that way, when you break the plaster away, it'll stop where you've cut it. Otherwise, as John said, by ripping/levering it off, you'll do more damage than you might want too. No problem ripping it off if you're stripping the whole wall.

 

[jrplastering]

john just a little thing for you if you struggle to feather in multi try useing a sponge float around the outside makes it a hell of a lot easier and it means you dnt have to faff around with it to much just get it on and flat then sponge it on the edge in a circular motion with a wet sponge and trowel it smooth then do the second coat about 2 inches further out than the first and do the same with the sponge, perfect feathering every time mate. hope that is of use to ya fella

 

[1john]

I may give it a go mate, have to buy a sponge float. The reason i do the one coat thing is that you can fill out upto 2" depth in one hit and it's all i have ever done lol.

 

[DrEvil]

Ta for the advice. Yes I did stop at the stuff that had a bit of rigidity to it - most of what I removed was crumbly to the touch.

Actually wondering if I should remove the wallpaper, a bit concerned that the paper is keeping quite a bit of the plaster in place quite nicely and wetting it to remove the paper may give me more trouble than I care for!!

Actually now think I will try to patch it as it without repapering (considering most of it will be out of view anyway) and if I'm not happy with it then will look into repapering that one strip.

Can seem some thistle one coat plaster at the local B&Q or Wickes (as well as Wickes own brand stuff)> Wickes stuff ok, or best to use Thistle? Also can see wickes own brand ready mixed jointing compound is that ok - all i can see at B&Q is bagged jointing cement or easifill.

 

[1john]

Wickes one coat is fine, wickes jointing compound is fine. also the easy fill is fine, just more mixing to do.

 

[DrEvil]

Numpty question, but joint cement isn't the same as jointing compound is it? But Easi-fill powder will do the same, right?

Anyone know if B&Q do a ready mix jointing compound?

 

[1john]

Not sure off the top of my head, i think it's called jointing compound in wickes and it's pre mixed, joint cement may be the stronger stuff that comes in powder form, generally used for spicking paper tapes and metal reenforced paper corners on and for filling out tapers. Dunno if B&Q do a ready mixed one, they do easy fill though which is just as good.

 

[jrplastering]

buy the powder easy fill mate if you get pre mixed youll be goin back to it 4 or 5 times as it shrinks back alot if you buy the powder easy fill youll only need to fill it twice, its much better stuff

 

[Peet]

As 1John says, if you lever and pick at it it'll just keep coming off. And off ....and off. If you lever it off the action will weaken and disturb the next piece along. Some how you've got to stop the rot, unless you want to replaster the whole wall.

Here's my technique for fixing this kind of thing.

The dodgy bit of plaster is cut out in a similar way to what roughcaster is saying, although my method is a bit more automated. I use an arbour to carry a small (4") diamond cutting disc spinning at slow speed in a battery drill. It produces much less dust than running the same disc in an angle grinder. It'll neatly cut out even very fragile plaster without disturbing it. I'd say battery drill only, never a mains one as they behave very differently. Cut out the offending part.

Then, and nobody has mentioned this yet, hoover out the hole to remove anything that's loose or dusty and PVA the edge of the old plaster and exposed brickwork. Water the PVA down 50/50 with water and use a cheap paint brush. A plastic 3L/4L milk container with its top cut off leaving the handle makes a good PVA carrier.

If it's very dry plaster PVA it twice. Then fill it in. There's no need to wait for the PVA to dry providing its not dripping with the stuff, although the instructions say it's best when the PVA has just dried enough to be tacky and that seems optimal. For filling deep areas use thistle bonding coat as the background suction has been reduced by the PVA. It's very easy to fill deep holes with. PVA its surface if you've left it long enough for it to dry out before applying the finishing plaster.

PVAing the hole improves the bound between old and new and helps support the old when its done. It consolidates the surface of the old plaster into something more stable. Otherwise you're attempting to plaster a layer of dust.

One coat plasters are usually very easy to use and easily sanded, although if you can don't build it up high enough to have to sand it. It's easier to build it up slowly, leaving the final coat as a thin uniform layer.

Be wary of your wallpaper thickness. If you plaster and level off to this the plaster is actually slightly raised away from the wall by its thickness. The only way to avoid that is to peel away the paper around the hole.

If you need a fine surface filler similar to polyfilla, then buy Gyproc Coving adhesive in the small white & green sack. It makes good filler and it's much cheaper than polyfila and doesn't dry out too fast in thin layers.

Hope that helps

 

[DrEvil]

Peet - that is very helpful.

I started stage 1 of the patching up yesterday actually. I've did hoover the old holes and peel back paper around the hole.

One main thing I didn't do was apply PVA, or use bonding.

I have gone for a layering approach using one coat plaster (did 2 coats yesterday, second one when the first had just a small bit of give and was slightly damp after around 45 mins). I'll prob need another 2 coats to fill the deepens holes.

I'm wondering if my approach without PVA will be ok?

It seemed to be sticking fairly firmly yesterday and I'll recheck today after 24 hours. But I don't want it falling out easily in a year or so - so if I have to I'd rather knock it out and start again to make sure it'll still be there in 10 years!

 

[1john]

On a small patch you could just damp down, if you are back to brick then its rare to find a dusty brick, using pva will make the plaster hold off from drying and when doing patch repair you dont really want that, it's more applicable to skimming over whole walls. If you leave the one coat alone for any amount of time that will make it dry out you could just give it a quick once over with a wet brush or a few squirts with a spray bottle just so the plaster you have already put in there doesn't suck the newer stuff dry.

[I have used one coat and jointing compound and/or easy fill to repair electrical chases hundreds, maybe thousands of times if you count each chase or accessory]

 

[Possel]

Since it is most probable that the plaster in question is lime not gypsum etc, I'm pretty disappointed that all you professionals haven't suggested using lime mortar to repair the damage with!

In my Victorian house I have found areas of modern plaster, cement based render (internally) and even plaster of Paris, and it's a right pain! It also stops the wall breathing properly.