How do I repair cracks in lath and plaster wall and ceiling?

[lbarr]

I bought an old brick California Bungalow about a year ago which had been painted.

About 9 months ago, cracks started appearing.

The wall is an external wall, there is also a crack below the window frame in the wall.

The ceiling looks like it has had previous water damage and is imperfect so I am not worried about the final finish.

Both wall and ceiling look like lath and plaster or dry wall?

I have bought Poly filler for large cracks but in the last few days the gaps have widened and it looks like the plaster is starting to come away (rather than it being just cracks).

My question is - will the poly filler be enough?

Could I silicone behind the plaster to make it grip and then use the poly filler?

Should I also use tape?

Thanks in advance.

[sara22au]

I'd recommend getting a building inspection done, since the cracks are continuing to widen. Repairing something that seems to be an ongoing and increasing issue is pointless unless you can determine the cause.

Sorry, but I don't think this is something a DIY fix is possible for....

[Jewelleryrescue]

@lbarr 

Sorry to say if your house was in an earth quake would you be  worried by the cracks or the wall  collapsing?  Your wall is actively  moving, cracks expanding please try to solve the movement issue first as you have multiple crack lines which is dramatic and no filler can  keep up  with that expansion rate.

I hope your house is ok.

[MitchellMc]

Welcome to the Bunnings Workshop community @lbarr. It's brilliant to have you join us, and many thanks for your question about repairing cracks.

Some good advice from our members here and a building inspection will be well worth the money.

Once you've established what's going on, it will give you a much better idea of how to move forward. Due to the nature of the widening cracks, I'd say it's past simply filling them. At a minimum, once the underlying reason for the cracks is resolved, you must chase out the cracks and open them right up by removing all the loose and compromised material. You'll then need to use a filler and fibreglass tape to fix the areas. If you are looking for a reasonable finish, I suggest getting a professional to do the job.

If you do attempt to do any work yourself, have the surfaces checked to determine if asbestos is present, as you certainly don't want to disturb the wall and ceiling if the materials do contain it.

Please let me know if you have any questions.

Mitchell
 

[lbarr]

Thanks for replying. We discovered broken terracotta storm water drain pipes on the other side of the house and a resulting rising damp problem which we've started to rectify. Obviously not previously maintained. The water wasn't pooling on the ground so had no idea. But a hygrometer and de-humidifier showed high humidity, thus also the explanation for the musty smell when it rains.
We're hoping this is the cause and just want to patch while we get through all the other stuff so the ceiling doesn't fall in.

Should we go for a stronger filler than the Poly filler?
Which tape would you recommend?

[MitchellMc]

Hi again @lbarr,

Unfortunately, an aesthetical patching isn't going to do anything more than mask the issue and make the area look better. It's not going to prevent the ceiling from falling in. If anything, covering over these cracks without chasing them out and removing all the degraded material will make it very difficult to repair in the future.

Sorry about that. I've fixed my link to the fibreglass tape above, but here it is again: Builders Edge 50mm x 90m Plasterboard Fibreglass Joint Tape. Polyfilla is suitable for the repair, but it's more about the prep work and removing of degraded material than the strength of the filler. Regardless of the strength of the filler, if movement is still present, it will crack again.

Mitchell

[lbarr]

Thanks Mitchell,
The main bedroom and hall has been treated for rising damp by removing the lower portion of the plaster wall and making a new damp course and no asbestos was found.

Thanks for your suggestions, I'll clean it out and get some tape too.

[MitchellMc]

You'll want to open those cracks right up by dragging the sharp edge of a scraper along and following them @lbarr. Chip all the loose material away from either side of the crack. If you are doing it correctly, you'll make the crack appear far worse than it already is. You can then fill the gap, place the fibreglass tape over the wet filler and then apply a skim coat of filler over the tape. Here's a helpful guide: How to repair a water-damaged ceiling. A similar method will be used on the walls.

Regardless of the lower wall not containing asbestos, please take all precautions with PPE, including a face mask, disposable overalls, gloves and safety glasses.

Mitchell

[Jewelleryrescue]

Hi @lbarr 

Thanks  for listening to us we certainly want to help your situation in the best way possible and save you money where ever possible too.

I was wondering what gave you the inpression the roof was going to cave in?  Do you just mean the plaster on the inside of the room?

I Think in any case you might want to add extra gyprock screws into the ceiling rafters and wall sheets to help stabalize the plaster to make  for a better repair.

I offer a highly elastic Gap  sealler  with 35% movement capacity.  How ever the edges of the plaster may still pull away under heavy movement under strain rather than this polyutethane sealer.

Sika 310ml White Sikaflex Pro+ Polyurethane Sealant - 310ml White I/N: 0083587

$23.22

This  sealer is  paintable but i would skim coat the wall with gyprock plaster after application as to give a  more smoother finish.  The new skim coat will crack if movement not stabalised.