Lath / Plaster Repair (noob)

[sourbrambles]

Good afternoon,

I was widening a hairline crack to fill but noticed a spring to the wall. I pushed against the spring and the wall began to crumble. I tapped the wall gently with a rubber hammer and the hole naturally got bigger but it's now as big as it'll get with gentle taps. How should I go about repairing this? I'd like to do it correctly.

Property was built in 1890s (granite construction) and some of the plaster does have hair in it so assume it's original. The lath looks in good condition overall and I've gone around the rest of the room and the rest seems solid e.g. no springing feeling.

If someone could point me in the right direction for products I should be purchasing and or guides I should be following that would be ideal

Cheers

 

[LadyArowana]

No need to bother really, just put a suitable frame around it and a nice raised gallery label.
Don’t worry someone will be along with a sensible answer soon.

 

[Cubist]

Notwithstanding Lady A's excellent lateral thinking, you'll probably find that some of the nails used to pin the lath to the wooden studs in the wall have rusted through. If you can locate the studs you could drive in a few screws to re-secure the lath to the studs before applying some new plaster.

 

[sourbrambles]

No need to bother really, just put a suitable frame around it and a nice raised gallery label.
Don’t worry someone will be along with a sensible answer soon.

View attachment 10502

 

[sourbrambles]

Notwithstanding Lady A's excellent lateral thinking, you'll probably find that some of the nails used to pin the lath to the wooden studs in the wall have rusted through. If you can locate the studs you could drive in a few screws to re-secure the lath to the studs before applying some new plaster.

I have strong magnet, assume I could find the studs nails / studs this way. Is there a general recommendation for type of plaster / lime mix? Should I be adding fibres e.g. coconut/ hair or am I being a little ott?

 

[sourbrambles]

Also thanks for the replies, I appreciate the quick responses.

 

[malcolm]

For a fix you would be best using lime plaster and pressing it into the lath so you get some go through which will hold the plaster to the lath. Lime plaster is better than the stuff you might buy at DIY shops as it is more flexible, but it does tend to be mail order in 25kg bags. I've been using this as it suits the repairs I'm doing over various surfaces and works on lath: http://www.anglialime.com/products/dry-ready-mix-mortars-renders-plasters/ecomortar-r50-2 You will probably need 2 or 3 coats to get up to finish level. No need for fibres.

Lime plaster has a larger grit size than modern plaster which makes it impossible to get a smooth finish on a small repair. What I tend to do is plaster to level then scrape the surface using a bit of wood or a steel rule resting on the surrounding plaster. Once it's dry scrape off any loose bits and finish with interior filler. I use this stuff: https://www.screwfix.com/p/toupret-quick-dry-filler-2kg/763pp Use that for the cracks too rather than lime.

I wouldn't go searching for studs. Lath doesn't normally fall away from the studs and you notice when it does. Minimal disturbance is best.

 

[Cubist]

I have strong magnet, assume I could find the studs nails / studs this way. Is there a general recommendation for type of plaster / lime mix? Should I be adding fibres e.g. coconut/ hair or am I being a little ott?

I've always relied on tapping or pressing on the wall to find the most 'firm' seeming spot then drilling a series of holes with a small diameter drill to find the vertical centre line of the studs.

Malcolm has already advised on the best plaster approach.

 

[sourbrambles]

For a fix you would be best using lime plaster and pressing it into the lath so you get some go through which will hold the plaster to the lath. Lime plaster is better than the stuff you might buy at DIY shops as it is more flexible, but it does tend to be mail order in 25kg bags. I've been using this as it suits the repairs I'm doing over various surfaces and works on lath: http://www.anglialime.com/products/dry-ready-mix-mortars-renders-plasters/ecomortar-r50-2 You will probably need 2 or 3 coats to get up to finish level. No need for fibres.

Lime plaster has a larger grit size than modern plaster which makes it impossible to get a smooth finish on a small repair. What I tend to do is plaster to level then scrape the surface using a bit of wood or a steel rule resting on the surrounding plaster. Once it's dry scrape off any loose bits and finish with interior filler. I use this stuff: https://www.screwfix.com/p/toupret-quick-dry-filler-2kg/763pp Use that for the cracks too rather than lime.

I wouldn't go searching for studs. Lath doesn't normally fall away from the studs and you notice when it does. Minimal disturbance is best.

Thank you for the thorough response. I'll order some r50. Is the toupret breathable? Or does it not matter for patch repairs?

 

[malcolm]

I've just tried spraying water on some Toupret with gypsum plaster around it and the water runs further down the gypsum. So more breathable than gypsum but I would expect less breathable than lime.

For a small patch repair it's not important. Though yours looks like it has been gypsum skimmed and painted with emulsion paint which won't be very breathable anyway.

 

[sourbrambles]

.

Thanks for the prompt response. Very good point about the gypsum skim and emulsion, I hadn't even considered that....makes the clay paint I bought a bit redundant as well

thanks again for your suggestions. I've bought both products now so just need to wait for delivery and I can get it patched. I'll need to knock a few more holes to get the use of the 25kg bag but I'm sure I won't have a problem doing that in the next year.

 

[Lacan07]

I have strong magnet, assume I could find the studs nails / studs this way. Is there a general recommendation for type of plaster / lime mix? Should I be adding fibres e.g. coconut/ hair or am I being a little ott?

The digital stud finders are more effective than a strong magnet imho.

I would use a product like Lime Green Ultra as the backing plaster, it's very light and good for lath. Push in hard with up strokes, never downward strokes. Then a fine putty based plaster to finish. To be honest if its an internal wall you could use Gyproc which will be much easier to finish flush to the old plaster but obviously not breathable.

Edit: I forgot to add you go 'across' the lath with the dub coat, so in your photo you go with 'upward' strokes

 

[fernicarry]

I recently tackled this sort of plaster repair for the first time. I use ready mixed haired coarse lime to fill most of the depth of the gap. Vacuum out all the loose bits and wet the laths and the surrounding edge thoroughly first. You might need to do this in a couple of layers to build up the depth. You want to fill to a few mill below the existing surface level, but this is quite hard to gauge when working 'inside' a hole. The haired stuff gets a strong grip on everything and even repairing a small area can quite significantly reduce the bounce around it. Then fine lime to finish it off. This needs to go on in quite a thin layer otherwise it will shrink and crack so if the coarse stuff isn't at a very consistent depth build up the fine stuff in multiple goes. If, like me, you struggle to get a decent finish with lime then use a bit of Toupret to make it presentable as per malcolm's suggestion.

If you want to find the studs poke something thin sideways in between the laths and measure how far it goes before you hit something. My studs are generally on 12" centres so once you find one you can pretty accurately map out the whole wall. Or, since electrical outlets are usually chased onto studs, you can start from one and work outwards. I tried a digital stud finder once but it just said everything was a stud. I think the walls were too dense for it. But no need to go back to the studs for this sort of repair unless you need to repair the laths themselves.

 

[sourbrambles]

.

Thank you for your response, it's very helpful. The wall has given up some more of its plaster so I've found one stud and the laths are still well attached so that's good. Do you think the addition of hair helped during the application? Also any chance you could share where you bought your premix? Looking for options for future.

Cheers

 

[sourbrambles]

Thank you for the directions, that all makes a lot of sense and with the other helpful responses I think I'm ready to take on the repair...once the plaster gets here.

Is there a recommended time to wait between layers or is it product dependent?

 

[fernicarry]

Do you think the addition of hair helped during the application

I think the hair helps it grip onto its surroundings, but I don't have a control point to compare with since that's all I've used so I could be wrong. I imagine it works like scrim tape. Whatever the mechanism it was surprisingly effective at stabilising bits that I was concerned might come away in even larger chunks.

Also any chance you could share where you bought your premix?

I used Wormersley's bought on Amazon and eBay. Very fast delivery and reasonable postage costs given the weight of the tubs. The Parcel Force guy did not look very happy...

You'll need to wait at least a few days between layers so it won't be a quick process.

Best of luck.

 

[Zebra]

You could hang around your local stables at grooming time and ask for what comes off the brush? Especially now it's spring, they'll be shedding loads. Couldn't hurt?