I am blocking up a small window today. It's about 2 by 3 feet and I
have some 'lite' blocks to do it.

The outside wall is rendered and painted so I need to get the finish
as flush as possible.

Can anyone tell me roughly what depth I should be looking to leave for
the sand/cement skim I will cover the blocks with. Obviously, too
thin and it is likely to just fall off but too thick and the mortar
may slump.

Any other tips? Other than pushing some newspaper down the cavity to
catch the mortar drops on the inside.

Thank you.
Rob


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Kalico wrote:
I am blocking up a small window today. It's about 2 by 3 feet and I
have some 'lite' blocks to do it.

The outside wall is rendered and painted so I need to get the finish
as flush as possible.

Can anyone tell me roughly what depth I should be looking to leave for
the sand/cement skim I will cover the blocks with. Obviously, too
thin and it is likely to just fall off but too thick and the mortar
may slump.

Any other tips? Other than pushing some newspaper down the cavity to
catch the mortar drops on the inside.

Thank you.
Rob


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I'm no plasterer but the last one I did I left 3/8" and sealed the
blocks with pva. The mortar was a bit reluctant to hang on at first but
bonded very well in the end with no cracking. Getting that final finish
to match the texture of the surrounding wall is a skill that still
eludes me.

On Fri, 14 Oct 2005 11:19:21 GMT, Stuart Noble
wrote:

[snip]

I'm no plasterer but the last one I did I left 3/8" and sealed the
blocks with pva. The mortar was a bit reluctant to hang on at first but
bonded very well in the end with no cracking. Getting that final finish
to match the texture of the surrounding wall is a skill that still
eludes me.

Yes I know what you mean about tying to match the texture, but in this
case I am not too worried about it. I'm leaving the soildier bricks
in place so it will be pretty clear that there was a window there
anyway.

Who knows, someone may want to open it up again in the future.

Thanks for the tip on depth though.

Rob


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Kalico wrote:
I am blocking up a small window today. It's about 2 by 3 feet and I
have some 'lite' blocks to do it.

The outside wall is rendered and painted so I need to get the finish
as flush as possible.

Can anyone tell me roughly what depth I should be looking to leave for
the sand/cement skim I will cover the blocks with. Obviously, too
thin and it is likely to just fall off but too thick and the mortar
may slump.

Either make it the same as the rest, or go for 1/2" (your blockwork
may not be exactly flat, don't forget). Damp the blocks and apply
your render, when it's gone off for a while and is setting, level
it off with a 2x1 planed batten (slide it from side to side as you
pull it up from the bottom of the blockwork), make good any hollows.
Remove mortar that's been transferred to the existing surface.

What is the original surface finish? What is the existing mortar
made of?

On Fri, 14 Oct 2005 12:58:58 +0100, Chris Bacon
wrote:
[snip]

Either make it the same as the rest, or go for 1/2" (your blockwork
may not be exactly flat, don't forget). Damp the blocks and apply
your render, when it's gone off for a while and is setting, level
it off with a 2x1 planed batten (slide it from side to side as you
pull it up from the bottom of the blockwork), make good any hollows.
Remove mortar that's been transferred to the existing surface.

What is the original surface finish? What is the existing mortar
made of?

The original surface is, I presume, sand and cement. It's on a 1930s
standard semi and painted over.

I had planned to use 5:1:1 sand:cement:lime. Sound about right?

Rob


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