Condensation

Published on September 19th, 2012 | by Henri

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Moisture builds up in remodeled house

Q. For 22 years, we have been living in a two-story home built around the turn of the century. Over the years, we have gutted and remodeled the interior, added a large addition, vinyl siding and, most recently (2 years ago) replaced all windows with high quality double-hung insulated windows with wood frames inside and vinyl clad exterior.

The insides of the windows were left natural and covered with several coats of polyurethane. At the same time, the bathroom (on the first floor) was also completely gutted and rebuilt with new walls, floor, ceiling and all new fixtures. Over the past two years, we have seen an increasing problem with moisture buildup on some but not all of the windows.

The big problem is in the new bathroom and upstairs bedrooms facing north. The windows in these areas are always moist during cold weather to the point that mildew forms on the wood frames and has to constantly be cleaned off. I am afraid this is affecting the wood and it will begin to rot. The bathroom is well ventilated with a high quality exhaust fan.

The cellar in this house has a dirt floor and a low water table. There is always water in the basement in the spring and I need to pump several times during spring thaw. My wife feels that the wet cellar is the cause of the problem and the cellar floor should be covered with crushed stone and plastic. This would be difficult because the ceiling in the cellar is only 4 feet high and there is no outside access except for two small windows. I disagree with her because the problem is only in certain areas and the rest of the windows are fine. Is it possible that the cellar is the problem and, if so, what is the best way to solve the problem?

A. Your wife is right. But there is no need to put crushed stones down; 6 mil plastic is enough. You may want to use two layers to be sure that, if anything on the soil punctures the lower layer, there is the top layer to keep the moisture out.

However, you need to control the water that gets in the cellar. This is best done by correcting any grade problems around the foundation and, if there are gutters on the house, by making sure that the downspouts lead water away from the house.

If you do not have gutters, make sure that there is some masonry (patio blocks, pavers, flagstones, etc.) at the drip line of the roof to prevent the formation of troughs dug up by falling water. The masonry you choose should be flush with the grade, which, itself, needs to slope away from the foundation by about two inches per horizontal foot.

Next, assuming water comes in at the base of the walls, make a small trench about three inches deep around the inside perimeter of the foundation walls and use the soil you remove to build a curb on the interior side of the trench. Lead this trench to a sump in the most logical part of the cellar (the best place to discharge the water outside). Dig a hole 30 inches square by 30 inches deep. Place 6 inches of egg-sized crushed stones in the bottom of the pit, put a 24-inch by 24-inch flue liner on top of the stones, and then fill the space around the flue liner with more stones. Install a high-quality submersible sump pump inside the flue liner, making sure its discharge flows away from the foundation so as not to re-circulate back into the cellar. Lay the plastic over the entire soil area of the crawl space but stop at the top of the curb.

Assuming that the cellar (which, at only 4 feet high, is really a crawl space), is not used much, there should be no need to protect the plastic from heavy traffic. But if there is need for frequent access to a furnace or anything else, it is advisable to put down some walking boards or use sneakers to walk carefully on the plastic.

By tightening the house over the years, and particularly by replacing the windows, you have reduced the movement of air through it, thus resulting in the accumulation of moisture. The reason only windows on the north side of the house are affected is because it is a lot colder on that side. and never gets the sun.

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