Heat and plaster walls?


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Old 02-04-11, 07:06 AM
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Heat and plaster walls?

We have a custom built home with plaster walls in Ohio. Some where back in time someone told me we could not shut the heat off or the plaster would separate and/or crack. We spend two to four winter months in the south and have maintained some heat to prevent this.

Recently a friend who is a carpenter asked me if we shut our house down for the trip south. Yep, all except the heat, then he wanted to know why we kept the heat on. I gave him the why and he told me that was not true. I've paid to keep the heat on for 11 years when I didn't need to?

We do drain the plumbing and even have the water meter removed to prevent any water from getting into the house. Also put rv anitfreeze in traps and toilets to prevent freezing in case of a power outage.

Have I wasted huge amounts of money keeping the heat on?

Thanks for your help!!

diks3220
 
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Old 02-04-11, 06:19 PM
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Is it a decorative plaster finish on a brick wall or is it a brick wall that is plastered and then covered with paint? Is it in the interior? Is there an insulation layer in the wall?
I know that some materials tend to expand and retract according to temperature, concrete for example. I painted a concrete roof slab with a concrete-resin mix in an external surface about a year ago and last time I checked it a month ago, it had some hairline cracks on it.
Apparently there is a calculation you can do in order to calculate the total expansion due to temperature change. For example you can check the "M.A.F. (Movement Accomodation Factor)" and some other stuff to get an idea of how much movement there will be and select a coating that is elastic enough. I never heard of plaster falling off from a wall because of the temperature change, applying a layer of primer before applying the plaster and good surface preparation might also help to make the plaster-brickwork bond stronger.
I would not leave the heat on whilst I am not there in order to protect the plaster walls I would probably just paint them with something else like an elastic latex coating or just paint them again if they get in a very bad shape That is with Greek electricity prices though.
 
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Old 02-04-11, 08:21 PM
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Is this plaster over wood lath? Gypsum lath? Masonry?

I think you should leave enough heat on to moderate temperature extremes. Here is why. The finish in the plaster is made of material somewhat different from the base coat. The base coat or coats is/are gypsum plaster with sand. The finish is lime with gypsum (gauging) plaster to harden it and make it set when it was applied. The very thin coat of finish expands and contracts at a rate different from the base coat(s). In time that different expansion and contraction causes delamination from the basecoat. I have seen houses that went through a year or so in the Great Plains that had the finish separate from the scratch and brown basecoats. In three coat work I have not seen the brown separate from the scratch because they are the same material. I suppose there could be other forces in play but I blame the cold. Now maybe if the house is well insulated so the temperature does not rise and fall much or frequently during the winter there will be less differential movement between the coats. All I know is I have seen what you are concerned about in unheated houses. I recon you could turn the heat on as low as it will go and keep the temperature pretty steady in the house and have no problem. If you did not heat the house how cold do you think it could get inside on the coldest night? If you did not heat how warm would it get on the warmest day? How many of those extremes would happen in the winter? I think it is the rise and fall and repeated accompanying expansions that do the damage.
 
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Old 02-05-11, 03:44 PM
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The house has plaster board/gypsum and two coats of plaster, base and finish which is swirled.

We are located in eastern Ohio and subject to sub freezing temps, some in the single it minus figures.

It was built in 1974 if that helps define the products.

Thanks for your insight!!
 
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Old 02-05-11, 06:03 PM
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A house of that vintage might, probably has veneer plaster. It is not very thick maybe 1/8" - 3/16" total for two coat work. Ask around. What has been others' experience?

I think if I am right about the plaster system it might be less risky than conventional plaster with a whitecoat finish.

Do you think that with a prolonged cold spell the house would get as cold as the outside temp? That is in the 20's or colder?

Plaster is not made for cold temperatures.

Go here Walls and Ceilings Message Board
Some old time, knowledgeable tradesmen hang out there. To post a question you will have to get an account. It's free and easy. Usually the people there are kind to amateurs and newbys. Don't pretend to be someone you are not. They can tell.
 
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Old 02-06-11, 07:24 AM
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Plaster and heating cont'd.

Sunday, 2/5/2011

I would estimate the plaster thickness for the two coats to be 1/4" +/-. The house is well insulated for all electric but I would suspect any prolonged cold spell, ie, sub freezing the interior temp would equal the exterior temps.

I really appreciate your help and have decided to leave the heat on to insure stability for the interior walls.

Thanks!!





Originally Posted by diks3220
The house has plaster board/gypsum and two coats of plaster, base and finish which is swirled.

We are located in eastern Ohio and subject to sub freezing temps, some in the single it minus figures.

It was built in 1974 if that helps define the products.

Thanks for your insight!!
 
 

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