At a neighborhood party I was approached by someone concerning exterior maintenance of his home in a nearby HOA community. The HOA requires owners to be responsible for all elements of their building and many of the buildings were experiencing water infiltration causing mold on drywall and other interior surfaces. He was aware I had experience in building forensic investigations, and he asked where the points of likely water infiltration were and how to find them.
He described his two-story home as being thirty years old with no history of major façade/ roof repairs or replacement except for painting the cementitious clapboard exterior siding several years ago. He said the siding and roof surfaces are in good condition despite their age. The home had vinyl coated double hung thermal windows and insulated fiberglass doors. The sloped complex roof was surfaced with architectural fiberglass asphalt shingles with several dormers, chimneys, valleys, and a few skylights. Soffit and ridge vents provided attic ventilation.
My first comment was that he should be aware most of his exterior home elements were approaching their anticipated useful life and will need replacement in the next five to ten years. He stated he did not know where the water infiltration was originating, and I said at this point neither did I. I proceeded to tell him how each of the exterior elements he described could fail and cause the water damage he is experiencing. I also warned him his problems may go beyond moldy sheetrock. Other systems within the exterior walls could be compromised including damaged electrical wiring, corroded deck fasteners, and structural wood rot.
First are the skylights. They should be banned. There should not be holes in your roof surface, especially big ones. Architects love them, contractors do not. Skylights are like motorcycles. It is not whether you will fall, but rather when. Skylights seem to always leak eventually. Even when the installer used the flashing kit from the manufacturer, something will go wrong and more likely due to workmanship rather than material quality. My only skylight rule is if you resurface your roof make sure you replace all the skylights whether you think they are in good condition or not. That way when they leak shortly after the new roof surface is complete you will know who to blame.
In northern states, the edge of the sloped roof on the non-gable elevations are often the source of water infiltration due to either ice dams or gutter problems. Ice dams are caused by unauthorized heat entering the attic space. The heat reaches the underside of the roof sheathing because the soffit and ridge vents system are not venting properly due to blockage or inadequate sizing. The heated roof underside melts the snow along the roof edge with subsequent freeze/thaw cycles causing ice to climb the roof slope under the shingles eventually reaching the edge of the incorrectly installed ice and water shield membrane. This results in melted water penetrating the roof sheathing and dripping into the attic and interior below.
Frank Lloyd Wright had the right idea. He banned gutters and designed extended soffits to shed water and ice away from the building. Gutters can be blocked by leaves and other tree debris and fail under heavy ice loads. However, in New England architectural design often includes the use of gutters, so we need to deal with the required maintenance.
Even roof flashing that has resisted leaks for many years can fail eventually with time. Flashing around chimneys and diverting crickets are always suspect but the most common flashing failure is at the kick-out flashings. Kick-out flashings are located at the edge of the roof where the sloping roof surface meets a vertical wall like a dormer or other architectural feature that should have ice and water shield running high up the vertical wall. Kick-out flashings are installed to shed water running down the wall away from the vertical wall’s base. Some building designs forget to install this important element or are installed incorrectly.
Building siding comes in a wide variety of materials. Siding is only a secondary defense against water infiltration. Siding’s primary function is exterior looks and mechanical protection for the building flashing, namely, the building wrap. This wrap (e.g. Typar, Tyvek, etc.) is often thought of only as a vapor barrier but it is much more important because when it is installed properly with seam tape and other manufacturers’ recommendations it seals the building from water infiltration that gets past the siding. It becomes a drainage plane directing water to weep holes or other exits. It works together with the window/ door flashing and sill pans to make a weather-tight facade.
Exterior leaks can be hard to find but knowing where to look first can save considerable time. Engaging an architect or engineer with building forensic experience can save both time and money. Beware of the contractor who only offers more caulking to correct the infiltration. Often invasive inspection techniques are required including removal of siding or roof surfaces to trace the infiltration’s water path(s). The use of moisture meters can be helpful. Spray testing may be necessary and/or infrared thermography camera images to pinpoint the problem areas. Whatever modern investigatory method is used, discovering the source of the infiltration is critical for selecting the successful method of repair.
Written by Jack Carr, P.E., R.S., LEED-AP, Senior Consultant Criterium Engineers
Published in Condo Media