My house is approximately 40 years old and has a low pitch roof (California style). Last summer I had a rock and tar roof replaced with asphalt shingles by a roofing company. With the cold winter and now our warmer temperatures I am getting water passing through and behind the walls and windows and it is dripping down the wall to the hardwood floors and then into the basement.
I have a ridge vent on the peak and soffit vents as well. I have cleared the snow off the roof to prevent ice jamming and still having water problems.
Could you please advise me as to why this is happening? I would appreciate any advice on a solution to this problem.
The answer to your question may be somewhat complex, but the simplified version is that the roofer installed the wrong type of roofing for the application. Regular shingles are not designed for use on a roof with a pitch less than 3/12 and may leak due to wind-driven rain and wicking up of moisture due to snow and ice damming. In the past, special “low slope” shingles were sold that were wider, had a larger overlap and had each individual tab sealed with asphalt cement. These are now rare to impossible to find and regular self-seal asphalt shingles are not a suitable substitute. I will provide suggestions for proper roofing installation that will help your problem leakage.
A “rock and tar” roof is actually a built-up membrane composed of several layers of roofing felt embedded in successive layers of heated bitumen material (asphalt). The rock cover is put on to prevent physical damage and deterioration from Ultraviolet light. This type of roofing is very high quality, but is very labour intensive to install. For this reason, it not commonly installed on residential buildings anymore. There are now torch-on and self-adhesive membranes available that are much quicker and less expensive to install. This is the type of roofing that should have replaced the old “tar and gravel” one.
The roofing may be improper and the main factor for the leakage, but a lack of adequate air sealing and ventilation in your roof may also be contributing to the water in your home. I am not sure what a “California Style” roof system is, but I am assuming that you are referring to a vaulted ceiling with insulation installed between deep rafters with a small air space above the insulation. Your description of the ridge and soffit venting suggest this. With this style of roofing system, there may be minimal air space for ventilation below the roof sheathing. This, combined with the low pitch, will be an ideal environment for ice damming. The minimal ventilation space may not allow enough cool air in to prevent melting of the snow, which causes the ice dams.
The reason that a built-up roofing system was installed in the first place is that it is a very impervious surface. It should completely seal the roof surface and prevent leakage when ice dams occur. It does not, however, prevent the ice dams from occurring and water may back up into the soffits and walls when the ice dams melt. This may occur if the eavestroughs are loose or filled with ice. Shovelling the snow off the roof and clearing the ridge vent may help, but increased ventilation and air sealing will be required to stop the leakage. The soffit vents and ridge vent should be continuous and open. You may be able to pull off the soffit vents and shine a light inside to see if the ventilation space may be blocked by insulation or other obstructions. Larger soffit vents may be required to allow more air into the roof system.
The underside of the ceiling should be inspected for cracks, holes, light fixture boxes, or any other opening that may allow air into the space between the rafters. These should be patched and sealed as well as possible, to prevent air leakage. The underside of the ceiling should be painted with a high quality paint that may act a partial air-vapour barrier, as well.
If the problem persists after these measures are taken, and it very well may, insulating and air sealing from the roof side may be required. This is a labour intensive and costly measure, but will ensure that the ice damming is kept to a minimum. The newer roofing and roof sheathing will have to be removed, the insulation replaced with a combination of blown-in foam and other insulation to properly air seal and insulated this area, while ensuring a minimum vented air space is present. Once this is complete and the roof sheathing replaced, the proper roofing may be installed, which should solve your problem. I would recommend completing the work before the next heating season, as major repairs to the moisture damage in the walls will be an added expense, if left unchecked for several years.