Hi all. I have a big gap in a lath & plaster wall and I will be using Bonding to fill it in preparation for a plasterer to skim it next week. I've never used Bonding before.
Is it stiff enough to lay a 12 - 15mm thickness on laths?
Does it go off quickly?
Can I use the 25kg bag over a 2-3 days or does it have to be thrown away on the day you opened it?
Thanks.
Arthur
In my very limited expertise, should be fine. Stiffness depends on how much water you add... The thing about bonding plaster is that it's stickier than other stuff.
Just close up the bag, it'll be fine. I've used it after a helluva lot longer than that after opening! It just gradually takes increasingly less time to go off as it ages until eventually it's unusably quick - but over a much longer timeframe than 2-3 days IME.
David
I haven't tried it on laths -- I fix plasterboard on them (or instead of them, depending on the thickness required). Then use bonding coat if I need to pad out the thickness further, and finish with finish coat.
As normally mixed, I would say 1/2" is the max you can do in one go. With laths, there's probably going to be less support, so you might find it more difficult to even manage that. Mixing up thicker than normal might help, but as I said, I've not tried using it like this.
You need to get it all on in perhaps 15-20 minutes. It will take
2-4 hours to set. This is for fresh plaster -- as it ages, it will set much faster, and in extreme cases, it will do it as soon as you pour it out of the mixing bucket.Providing you keep it dry and resealed, you can use it for months. They have a use-by date on the pack, but it's not precise and it depends much more heavily how it has been stored. You can find an opened pack which is still usable well after the date, and conversely you can find one which isn't usable well before the date.
An old stale pack can be useful for small jobs such as filling in wall chases, where having it set in 10 minutes is an advantage as you can then skim it without waiting around for hours for it to set.
I'm not expert on this but from my personal experience, you should be fine. Assuming the laths are dense enough to hold the bonding onto them (i.e. doesn't fall through) I would PVA the whole area first to seal it before applying the bonding. The bag will be fine provided you keep it dry.
Instead of bonding, have you thought about cutting out a "square" section and fitting some plasterboard onto the uprights instead (you will probably have to fit a couple of noggings too)? May be easier and provided you screw it in, I would suspect there would be little movement on the joint to cause cracking.
I just keep chucking it on till it slumps, then leave it for an hour and try some more.
It starts to firm up after a couple of hours, but can take a few days to actually dry.
I'm still using a bag I bought last year :-)
You can get "lite" or "one coat" plasters that won't sag at 15mm, and dry more quickly, but they're expensive. Depends how big the hole is
The main area requiring repair is a big nonsense of a shape sort of spreading in 3 directions so I would be cutting and snapping off bits of plasterboard for ever.
Excellent info from all. Thanks.
Arthur
rather than cutting the pasterboard to size, you could take the outer edges back to the nearest upright and cut it into a square/ rectangle then plasterboard that. I used an old hand saw which was Ok going through the plaster then a decent saw for the laths once the plaster was removed.
Bonding goes off slower than the fine finishing plaster - this is to give you longer to work it It is also lighter due to the small vermiculite granules used to bulk it out. You can use it weeks or even months after opening as long as you keep the bag dry like somebody else said the setting time reduces with age until it becomes virtually unusable - but even then I've used it to fill very deep holes. the quick setting time in this application is an advantage as you can build up quite a depth very quickly.
When repairing a hole in lath and plaster it is very important to use watered down PVA (approx 4:1 water:PVA) over the whole area but you must pay particular attention to the edges of the old plaster going round a few times brushing in loads of PVA so that the excess is pouring off in rivulets. If you don't do this, the old plaster will suck moisture out of the new bonding very quickly causing the bonding to shrink away from the old leaving you with a crack and poor adhesion. So the glueing needs to be done just before you do your plastering.
Plasterboard is great for large areas or whole walls but I wouldn't fiddle about with it in this application - far too fiddly
I've had it on 2 inches thick in places, without slumpage
on L&T about an hour, maybe 90 mins.
it will last indefinately, but the longer you have it, the less setting time, IE if it's very old, expect it to set within a few minutes of mixing. There will be a best before date printed on the bag
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