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Polystyrene fire risk?


Jackie
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For reasons I won’t bore you with here I had to take up a floorboard in the grenier next to the wall. I was somewhat surprised to find that the previous owner, on rebuilding this place, had clad the outer wall in thick white expanded polystyrene sheeting. There is then an air gap of  2 to 3cms and then an inner wall of this thin, hollow red brick stuff.

 

The surprise was that he had continued this polystyrene cladding across the inside of the outer wall where the chimney runs up.  Now ok we have a wood burning stove with a metal liner running up all the way up of the inside of the chimney proper but this outer wall in front of the chimney gets quite warm when the stove has been running for a few hours. My concern is that lower down, I can only feel this wall in the grenier as there is no inner wall there, the wall must be even hotter and the polystyrene is, I believe, flammable.

Should I be concerned or not? From what I can see there are no signs of melting. We will have the stove replaced soon so I could take down the bedroom inner wall to remove the cladding then if need be, big job though!…………………………..John not Jackie   

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Polystyrene is very flammable and produces a very high temperature flame when it burns, it also drips flame as it burns, thereby spreading a fire.  However, it is used as a building material in ceilings and in walls for insulation.  I would if possible keep it well away from any source of naked flame although heat from a chimney would probably just melt it.
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Thanks for coming back on this Ron. From what you are saying I take it that I should not worry too much as the only way it could be exposed to flame would be if there was a hole in the liner and one in the chimney wall. Having said that I know there must be at least one hole in the chimney up in the grenier as all the bees that live between the liner and the chimney come into the grenier through the wall each winter when we light the first fire in the stove. I suppose there maybe other small holes where the cladding is lower down. My only alternative would be to demolish the inner wall and take out the polystyrene, not a five minute job really!.....................................John
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