I hope you can help us solve a mystery to a problem that we’ve been having since our new house was built, which is close to 3 years now.
We have a great room where the ceiling is 2 stories high and it includes a dining room in the front and a living room at the back. We have 2 sets of identical windows on both sides, a large rectangular window is on the second story and another window of the same size is below. When we get torrential rainstorms accompanying high winds, water drips down in between the window frame and the window coming in at the top of the lower window. Depending on which the direction the wind is coming from, this can happen in the front of the house or at the back of the house but the problem is the same on both sides.
When the house was being built, I noticed there was water on the plywood floor after a rain and the builder said because the stucco was not put in place we will get water coming in and once the stucco is applied the problem should be resolved. This did not resolve the problem and since then, the builder has tried caulking around the window both the upper and lower windows on both sides of the house and this has not resolved the problem. We have tried using water to spray around the lower window and we cannot re-create the problem. The problem only occurs in heavy rain and strong winds.
The builder has brought in the people whom we have purchased the windows from and since they think it might be a problem with the Tyvek around the window it would be too late to do anything. They recommend that we use a sealant that is widely used in Vancouver to spray over the stucco on both sides of the house. This sealant would provide a barrier over the stucco and prevent moisture from getting in.
Could you tell me if you would be able to guess where the problem might be, whether the sealant would work and if the sealant is safe to use and not cause other ventilation problems for the house? Another concern I have is that what kind of knowledge and experience must one have before putting on this sealant properly, since it is not commonly used in Winnipeg?��
One of the most difficult problems to solve in newer homes is leakage from windows. This is a very common complaint, but unfortunately may have one of several causes. We will explore these possibilities and answer your question about the sealant.
There are three main areas that water can be entering to cause the leakage that you are experiencing. The first area is the windows themselves, or the area around the thermal seals. This is most common with operating windows, such as casement, awning or slider units, but may also occur on fixed windows. This is often the most difficult to diagnose, because the window manufacturers rarely admit there may be a problem with their product. There are normally small weep holes at the bottom of the frame in a vinyl window, and sometimes these may be blocked or plugged during or after installation. This is the first area to check. If these are OK, you may wish to try a test with a pressure washer on the window itself, rather than just a garden hose, which should simulate the driving rain better.
The next possibility is the area around the window frame. In modern windows there is a gap or space between the window frame and the wall framing. This allows for expansion and contraction of the window, but it must be well sealed to be effective with the insulation and vapour barrier of the exterior wall. This is most commonly accomplished by filling the void with low expansion foam insulation. This foam should be sealed to the vapour barrier on the inside of the wall and should fill the entire cavity. Some installers still use the older method of stuffing small strips of fibreglass insulation into this gap, which will not provide the proper air seal and not prevent moisture intrusion. This can be checked by pulling off the inside window casing and inspecting this area with a flashlight. If the area is not filled with foam, or has damp fibreglass insulation, that is the answer.
The final possibility is the exterior area around the window, the flashing or the housewrap (Tyvec) and improper installation. The windows must all have a metal drip flashing installed over top, and some installers skip this step, thinking that the vinyl nailing flange is sufficient. This metal flashing can be easily seen over top of the window. If this is in place, the installation of the housewrap may be improperly done or missing. The housewrap should be installed over top of the drip flashing, so that any water that drains down this exterior membrane does not leak behind the flashing. The hard part about this possible situation is that this defect may only be determined by partial removal of the stucco. That is a step that may be inevitable, if the first two possible causes are disproved.
Finally, spraying any kind of sealant over the stucco may be useless or possibly detrimental. Traditional stucco is a breathable siding material that has to be allowed to dry out after wetting. If the stucco gets wets, this coating may prevent the moisture from escaping, causing damage to the stucco. I would not recommend use of any products like this, especially since our climate is dramatically different from that of the west coast.