Re: HELP! Water in walls, no detectable source
If your wall plaster is upon expanded metal lath moisture readers are going to register (falsely) high readings behind your plaster even if there isn't a moisture issue.
I agree with previous poster about the pointing work and painting likely contributing (walls can't respirate). Window and wall flashing might have been damaged also.
You'd have to know if your plaster is applied directly on the brick, or on wood lath (on strapping), expanded metal lath may be with strapping usually not, or on gyp or rock lath (on strapping over brick), I've seen all three in DC circa 1900-1950 construction (and once all three in the same row house).
Source might also be between the wythes (layers of brick in the wall) up near the shared walls or roof. You probably have three wythes on two walls and two on the other walls.
If the problem is only on the lower floor then suspect plumbing traveling along the ceiling out to the wall then down the wall behind the plaster. Do you have old style expansion tank up in the attic for the old boiler or any steam/hot water piping up there that is another potential source of moisture between floors that can travel in the cavity and pour between inner brick wythe and plaster or down inside walls.
Is your bathroom exhaust fan vented to the outdoors or to the attic cavity?
What are you doing for cooling/dehumidification in the summer? A/C? Where is the coil, the condensor? Draining condensation or a pan might be the source depending on where your appliances are located. Other thought is that windows open/window sills are the source - i.e. rain - but not so much if this is only inside walls not exterior walls to the row house. Perhaps you have storms up or windows closed and that's the reduction of the smell or perhaps no AC running is the difference (condensation pan or drain line).
Last edited by Gray Watson; 11-18-2009 at 07:08 PM.
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