Filling in a wall chase

[jesteh]

Hi,

I had couple of chases on aerated block (Celcon) I was going to fill in. Wall is sand & cement with thistle multifinish top coat.

They are not big chases and I thought I can do this myself . So I got a bag of hardwall, bag of multifinish and got started.

Got the chases wet with a brush and started shoving hardwall in. Done that bit of a job and went for a break to let it set a bit before I put multifinish. Came back an hour later and hardwall was still in the chase but with clear edge line where its didn't bond to the old plaster, I suspect it didn't bond to the back wall for the same reason.

So where am I going wrong? I possibly mixed it too stiff which may be the whole reason but not sure. Help .

 

[PrenticeBoyofDerry]

Background preparation
Surfaces should be reasonably dry, clean and protected from
the weather, and suitable for the chosen specification. In
addition, some masonry backgrounds of exceptionally high
suction may require pre-treatment with Thistle GypPrime to
control their suction.