render/plaster question

[johnad]

I am in the middle of rendering a chimney Brest
All the old render was striped off and I have now rendered the brickwork with sand/cement my question is should I top coat with sand/cement or plaster finish?
Will the scratch coat pull the water out of the top coat making it hard to work as I recently used a bonding coat on another project and when putting the finish on it was a pain to work properly as it was drying out even when wetting the bonding coat 1st
Help please

 

[trowelmonkey1]

if you want a nice smooth finish then you need to skim it with finish.

PVA (diluted 3:1) it 24hours before you're going to skim it, this will control the suction.

PVA again immediately prior to skimming, making sure you skim while tacky, this will give the skim extra adhesion.

 

[Richard C]

What if any stove are you having? Gypsum plaster (base or finish) won't stand much more than 50 degrees C so it's important that the area within 300 – 500mm around the stove is finished with the correct materials or it will crack & fall off.

 

[johnad]

I will be having a log burner installed the opening is in brick so the front of the chimney Brest only will be finished as I said I have already rendered the scratch coat with sand/cement will a top render coat be better then ?
I would like a flat finish but not bothered if it has that polished look of plaster as its an old cottage with timber beams and rendered walls but I would like a reasonably good finish so the fireplace stands out from the rest of the room.
What would be easier to work as an amateur I have done quite a bit of plastering and rendering to a good standard but as I say not a professional.

 

[Richard C]

This stuff is good but rather pricey;
http://shop.vitcas.com/vitcas-heat-resistant-plaster-16-p.asp

A sand/cement/lime render will work just as well for the base coat; not sure how well it will cope without the lime. Don’t use Gypsum plaster within 300mm either side or 500mm above the stove as the wall temperatures in this area can easily exceed 70 degrees C with Multi fuel or wood burning stoves; Gypsum based plasters will crack & blow at these temperatures.