One or two coats??

[dlacheson]

I've got two chimney breasts to set and finish. It's to be rendered in sand and cement first then skimmied with multi-finish. The skimmining is no problem, it's the rendering, would one coat be enough then finish, or should it be two coats? Advice anyone?? The breasts are of brickwork, weather struck pointed, which looks quite neat actually, I don't understand why she wants it covered!

 

[Chris W]

make sure the breasts are vented first, if theyre used its no problem but if theyve been blocked off they need venting at the bottom and again at the chimney with a vented cowl.
1 coat render should do it, long as you can rule it flat and get a half decent float on it, its gonna be skimmied after all
why not just dot and dab em? quicker and easier for a novice...

 

[dlacheson]

Thanks Chris, the customer doesn't want the hollow sound of dot and dab, but that would have been the prefered method. No need for vents as the opening is staying. By the way, am I right in saying that the joints of the brickwork should be raked out? as I was told not to bother. And one more question, Should I PVA the brickwork prior to rendering?

 

[Chris W]

raking out would help with a key if the brickwork is dead smooth..
a very weak pva would help if theres loads of suction...
if the only problem is hollow sounding boards, why not use hardwall for medium suction or bonding for low suction? much easier than rendering....
bagged, mix up in buckets or a bath with a whisk...
skim it that afternoon....

 

[dlacheson]

I thought about bonding or hardwall, but was told to use sand and cement because if the chimney isn't blocked off at the top and water comes down, it would penetrate through the brickwork and the bonding! I find this hard to believe but who's right?

 

[Chris W]

render wont stop penetrating damp either...
just stick a cowl on top of the chimney pot, job done...
if the fireplace is in use as an open fire render would be the best option though..

next time it rains go stick an empty paint tin in the garden...
thats how much water comes down each open flue every time it rains..

 

[warriorupnorth]

Surely that would depend on the size of the paint tin ??? and whether the lids on :

 

[oasis]

I'm like a big sponge soaking all this info up for the next time

 

[lucius]

I wouldnt bother raking out if the weather pointing is sound leave it you will only disrupt the brickwork by trying to hack out sound pointing, dosent need pva just give it a good drink of water and maybe some water proofer in the render if you want to slow down the setting time of the finish.
Lucius.

 

[iain_flanagan]

best check that it hasnt had the brickwork sealed with anything if its been decrotive brickwork