The following refers to a two story frame house with basement in upstate New York, the "new" part of which was completed in 1820.The exterior wall is wood clapboard on the outside and wood lath and plaster on the inside. In 1930 a brick chimney was constructed on the outside next to the wood clapboard, and is connected to an oil burner [furnace] in the basement. The house is now closed during winter and open only in summer months. In the last few years there has been moisture on inside of the wall in the chimney area. This may be only leakage from chimney flashing, or ice formation under eaves, but since the house is closed and unheated in winter, could it be bricks retaining moisture? When re-papering and plastering should a moisture barrier be put on the chimney wall, or would moisture be trapped either on the clapboard side or the inside wall and ultimately produce dry rot?
I have heard that the Carey Bros. indicate that improper use of moisture barriers can produce problems in dry rot. Is this such a case?
It sounds like your house is old enough to go back to Louis the Fourteenth... that is unless you pay him before then! Ba Bump Bump!
Actually, you have all the answers written into your question -- you just didn't realize it when you sent your letter. By adding a moisture barrier to the inside surface of the wall you will stand the chance of creating a rot problem. Moisture will condense on the outside surface of the moisture barrier (the inside face of the wall studs) trapping moisture against the studs, and eventually causing a fungal growth, and yes, this can happen even on a house as old as yours.
The clapboard is a good moisture layer, and doesn't sound like the culprit. Our guess is that the flashing you mentioned is probably leaking. The flashing can be easily checked for leaks with a water hose -- in the summer time!
There shouldn't be any heat transmission from the chimney to the exterior wall. If there was heat transmission from the chimney to the wall it could cause condensation. If this were the case (and we don't think it is) a heat barrier (constructed from drywall, or mortar or sheetmetal) would be in order.
