Patch of hollow plaster, uncovered unknown material... help!

[Petebriz]

Hi all,

Firstly this is my first post so please bear with me.

After removing some horrible shelves in an alcove in preparation to re-paint and spruce up my dining room I've discovered a patch of plaster that sounds very hollow when knocked (the wall around it sounds fine). After painting it white in preparation i noticed a darker patch was showing through so new that further investigation was needed. I cut out a little section to investigate what was underneath, the top layer came off very easily and underneath looks like a sort of cement which is also crumbly (see attached photos).

I was wondering if anyone could identify what this is and the best way to go about fixing it? The total hollow sounding patch i about 30 x 45 cm. Please note that the images are displayed horizontally when they should be vertical.

dining room alcove 1

• Petebriz
• 21 Jun 2012
• 2

dining room alcove close up

• Petebriz
• 21 Jun 2012
• 2

dining room alcove 3

• Petebriz
• 21 Jun 2012
• 2

Many thanks in advance.

Pete

 

[Burnerman]

It just looks like an ordinary cement or thermalite block wall Pete, with plaster layers on top as per the norm......occasionally the plaster does 'blow' away from the substrate beneath.
The likes of B&Q etc do ready mixed patching plaster in tubs, which will happily fill that (but not necessarily in one go).
John

 

[JohnD]

how old is the wall?

 

[Petebriz]

Thanks for the replies guys.

The house is from around 1880-90 which i've recently purchased. the wall is the far corner wall of the property and it is end of terrace. I'm guessing from your assesment of the material that it is not the original wall/material??

So... to repair do you think it would be best to cut around the hollow plaster section and remove the plaster. The apply ready mixed plaster, sand and paint?

The cement or thermalite block is quite crumbly, should i try to disturb that as little as possible when removing the plaster and reapplying? I'm concerned the patch will come back!?!?

Thanks for your advice so far, it's much appreciated.

Pete

 

[JohnD]

It looks to me more like lime plaster, which fits the age of the house. You should hack off the loose and repair with lime, not modern gypsum plaster. You may find it easier to use as it does not set so fast. When you have hacked it off, look for any cause such as cracked brickwork, nails or screws driven in, or water ingress, and fix the cause.

Lime plaster is usually quite thick, an inch or so, and greyish-white, not pink or smooth grey. That's why I asked the age of the wall.

 

[Petebriz]

First off, apologies for the duplicate post. I thought it might be better placed in the building section but couldn't see a way to move it over.

JohnD - thanks for the detailed response. Lime plaster sounds likely as it is a greyish white colour. I'll hack it all off and have a look, where the material underneath (lime ash?) has crumbled off would it be best use a filler before the lime plaster?

I'll have a look on the outer wall but I don't believe there are cracks in the render on that wall.

I mentioned in my original post that I removed some horrible shelves prior to painting, these were held in with big bolts (about 1cm x 8cm) and were located above and below the patch. Is it possible removing these could have caused the issue, allowed water in??

Thanks for your help.

P

 

[JohnD]

putting nails, screws or bolts in, or pulling them out, might have started a crack, and the steel might have expanded as it rusted over the last hundred years.

peaps had some good ideas on your other thread.

 

[peaps2]

Inspect your gutters and drain pipes to see if they are ok. Look at the pointing or render on the outside as well. Looks like you have a damp issue as well.

Ash lime was commonly applied to outside walls (gable-ends) to add strength to the wall.

When you have sorted the damp issue out you can hack off the blown plaster and re-do it, I would use lime render and add some lime to the skim.

Is the wall single brick, 9" solid or cavity?

 

[Petebriz]

Thanks for the responses.

The first thing I did was check the gutters and drain pipes and all seem clear and in good working condition. There actually is a small crack in the render on the outside wall but nowhere near the corner where the patch is. It's strange as I have no other damp issues in the whole house and then this patch suddenly appears.

I think it must be related to taking the bolts out as it wasn't apparent before then. Now i just have to work out how sort this 'damp issue', maybe filling the bolt holes with something better than polyfilla. If not I might need to get a pro in?!?!

Oh and i'm not really sure on the wall material. The room upstairs is single brick so i'm guessing this is as well.

thanks for all your advice so far.

 

[Petebriz]

Actually I think it is a 9" solid brick wall.

Cheers,

Pete

 

[peaps2]

Actually I think it is a 9" solid brick wall.

Cheers,

Pete

can you post pics of the outside wall?

 

[Petebriz]

So i've finally had time to have a proper look outside and take some photos. Peaps i think you're right about the render, I can now see there is a thin crack which is in the same area as the patch inside. I've taken some photos and highlighted the area where the patch is to try and help.

I think this means i'll need to get the crack sorted before doing anything inside? is there something i can do to fill the crack outside or is this a job for a pro?

many thanks for your ongoing assistance.

Pete

ext view 1

• Petebriz
• 24 Jun 2012
• 1

ext view close up

• Petebriz
• 24 Jun 2012
• 1

inside view

• Petebriz
• 24 Jun 2012
• 1

 

[peaps2]

hack it off and have a go with lime render, do it yourself. if you are going to have a go let me know and i will go through it with you step by step