plastering 3 inch deep hole in wall. How?

Postby jetblack » Thu Dec 18, 2008 9:00 pm

Just had some electrics done in my kitchen and i now need to fill in the areas chased out for the wiring. The area is, in places about 3 inches deep and the channels are about 6 feet long. Whats do i use to fill the channels?

I bought some ready mixed plaster and tried to slap it on but felt that it was't really filling the depth of the holes or adhering very well. was worried the filled area would be 'soft' and would push in with if any pressure were put on it when dry so i took the plaster back out.

The wall is breeze block with plaster on top.

Any advise on how to tackle this job would be appreciated!
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Postby kbrownie » Fri Dec 19, 2008 12:59 pm

A few different materails are available, must be a hell of a chase for cables if 3 inch deep! This is how i'd do it:
1) clean any debri/dust fron chase
2) apply a dilute 4 water to 1 pva on area you are repairing and leave till tacky (not dry or wet)
3) browning or base coat plaster in to chase, leaving about 3mm step back from level of wall, score this and leave awhile to dry about an hour.
4) Then apply finish plaster again leave about a 45mins and smooth off with trowel and again leave 20mins and wet and polish off to level and smooth.
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Postby jetblack » Fri Dec 19, 2008 8:43 pm

So its ok to apply finishing plaster to a base coat that's not fully dried?

I've finished the base coat but its starting to crack as its drying out. does that mean i've put it on too thick?

The holes are still pretty deep as i didn't want to trowel the base coat in too thick...i was going to let base dry over night then do another layer, then do the finishing layer.

the holes are so big as its where the old sockets used to be (they've had to be moved)

Bit worried that i should have filled the holes with Mortar first to give a more stable base...?
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Postby kbrownie » Sun Dec 21, 2008 4:19 pm

It's okay to apply finish while base coat is still drying out as long as you have left it long enough so there is no movement in it.
But nothing wrong in letting it dry as long as you apply a coat of PVA to base coat and level it to tacky before applying finish.
Socket-outlet base can be filled in with base coat, if really deep may need to apply it twice.
If base coat is cracking as you say mix could be to thick. When mixing base coat it's seem times hard to gauge if you have never done it before, as the mix is quite light and fluffy. The trick is to add it to water and at the point the mix can stay on your trowel without slipping it should be okay.
When you apply finish it should trowel in to cracks and make the mix quite wet like yougart
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