Skim plaster falling off wall due to heat.

[alanfrank]

Can anybody advise me please? About 4 or five months ago I had a room reskimmed over sound, solid plaster. About six weeks or so after plastering, when fully dried out I painted walls with three coats of a quality emulsion. Several weeks later I had a wall hung, flueless gas fire fitted directly onto the wall. The fire has a convector type grill on the top from which warm / hot air emanates. I did not turn the fire on until today, 5 months after the wall was skimmed. After about an hour I walked into the room to find that the plaster above the fire had bellied out, cracked and was falling off the wall in the area it was subjected to the warm air.
There were no instructions with the fire that some sort of heatshield should be fitted and the picture on the box displays the fire hung on what appears to be a plastered wall.
Can anybody tell me;
a) Should this have happened? It has never happened before when I have fitted central heating radiators over fresh plaster.
b) Has this happened as a result of a faulty mix or application of plaster?
c) What can be done to prevent it happening again if I have the wall reskimmed?
Appreciate your views.
Thanks
AlanFrank

 

[Richard C]

a) Should this have happened? It has never happened before when I have fitted central heating radiators over fresh plaster.

Unfortunately your not comparing like with like; conventional C/H Radiators will not heat the surrounding wall above 49 degrees (see below).

b) Has this happened as a result of a faulty mix or application of plaster?

Not in itself; it may be unfair to blame the plasterer if he was unaware of what was to be fitted but many inexperienced plasterers are not fully aware of the limitations of conventional Gypsum plasters anyway. You need special heat resistant screed & plaster if the operating temperature of the appliance will heat the surrounding walls above 49 degrees; conventional Gypsum plasters will not withstand exposure to heat above that & will crack & blow as you have unfortunately discovered.

c) What can be done to prevent it happening again if I have the wall reskimmed?
Appreciate your views.

Strip it back at least 300mm around the stove & use a heat resistant screed as a base coat (or sand/cement/lime render base), with a heat resistant plaster finish;
http://shop.vitcas.com/vitcas-heat-resistant-plaster-16-p.asp

 

[alanfrank]

Richard, Thanks for your response. If I chop out the area affected by the heat, rescreed and skim with heat resistant plaster do you think it will be possible to blend the new heat resistant plaster in with normal plaster on the unaffected areas or does it have a diffent 'finish'. The wall is about 15ft long and loking at the price of the heat resistant plaster it would cost an arm and leg to skim the whole wall.
Thanks again
alanfrank

 

[Richard C]

Yes it’s possible but how good it will looks a matter of individual skill; It would be unrealistic to skim the whole wall with HR plaster but make sure you cut back far enough so the heat wont affect it.

 

[alanfrank]

Richard, Thanks again. Your reply was pretty much what I expected but not what I wanted to hear! I don't think I have much choice other than to change the fire for a different style and reskim the wall. Thanks for taking the time to help.
Alan