PLASTER LAID ON THICK

Have no problem skimming half decent walls but has anyone any advice on skimming a wall where some of the old plaster is blown and render falls away. Have built areas up with backing plaster (carlite) but struggle to gain same results when laying onto these areas as u tend to have to build it up a bit thicker.

 

What i mean is the thicker areas do not close down so well. or am i closing it down to soon

 

Hi Brist,

What do you mean by closing down? Do you mean flattening or after laying on the two coats or is closing down something else? I usually do the following:

First coat, wait a few minutes, second coat, wait for it to stiffen up a little, flatten, wait for it to pull in, splash and trowel, wait a while, splash and trowel again, wait a while again, trowel.

Are any of those closing down?

I have noticed that on surfaces where suction isn't great some areas tend to pull in slower than others creating a rippled sort of effect which seems to reduce as the plaster dries throughout. However, there have been times when the ripples remain, albeit much less noticeable.

Regards

Fred

 

If your referring to different rates of absorption over the patched areas, this can be problem; I double or triple coat these areas with PVA immediately prior to skimming which helps slow things down.

Re Freds ripples on low suction areas; this usually happens where the plaster is a bit on the thick side & continual troweling can make things worse if the plaster is still too soft; if you leave them alone until the plaster is almost totally set & then polish them really hard with plenty of water you can flatten them off to the point where they won’t notice.

 

Cheers guys sounds like good advice.

 

Hi Richard,

Sorry, ripples is probably the wrong description, it's more of a mottled effect than a rippled effect. I meant to say in my post that it was almost as if the skim's too thick but I know for sure that the skim wasn't too thick, if anything I'm usually guilty of laying it on too thin. I tend to get about 15 sq m out of a bag because I lay it on so thin!

Regards

Fred

 

Same here, i occasionally get away with single coats on board too!
It sounds bad, but if the boards are up nice and level you can still get a very reasonable finish and it goes off much faster allowing me to be down the pub earlier.
I think the mottled description is what i call stinging nettles cus it looks like your arm when you have been stung?
I get this on PVA quite a bit. I think maybe its too much PVA that causes this, the areas with it do take longer to go off.
When on PVA i also make the mistake of getting palster on too thick and then trying to trowel it about causing the ripples.
All just experience i spose.
The stingers do come out when its almost gone off and you trowell over with plenty of water.
Anyone use a spray bottle? Started doing this recently and it makes things a lot easier.

 

The stinger as you call them, yes, they're the ones I get sometimes too. A right PITA! Maybe it's just my impatience, laying the plaster on too soon before the PVA has dried a bit.

As for spray bottles, I use them sometimes too. Mainly when mess is an issue. If I'm in a confined space or if water running down the wall onto skirting and under sheeting is an issue then I'll use a spray instead of my splash brush to control the amount of water I use. I do like the brush though. It's also a good little cheat if you've got a rough patch because I run the brush lightl over the patch and it helps smooth it before running the trowel over.

regards

Fred

 

I've got a nice big 1 litre one & use nothing else.

 

Richard,

Is that one of the pump to pressurise ones? I imagine that makes it even easier than the trigger operated 250ml one I've got.

regards

fred

 

No just triger operated.

 

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