I have a question that I am often asked by my clients that I don’t know how to answer. It is regarding stucco on the underside of eaves on older homes. I have observed stucco on soffits on many older homes, including my own. Can you tell me what the purpose of applying stucco in this area is? These soffits have no apparent ventilation and I am concerned about possible moisture problems in the attic or walls in the home. Is this a potential problem in this style of home? If so, is there any way to improve the situation and increase the ventilation?
I am not sure what the reasoning was behind installing stucco on the underside of eaves, except to prevent the regular painting required of wooden soffits. You may not be able to give your clients a better explanation than that for the presence of the stucco, but you may be able to help them with the ventilation concerns. The only concern I have seen with the stucco itself is when it becomes loose or sagging due to a roof leak, moisture build-up in the soffit or rusting fasteners. In this case removal of the damaged stucco is the only solution to prevent the hazard of it falling to the ground below.
The soffits are the horizontal surface on the underside of the section of the roof overhanging the exterior wall. These soffits may be covered with tongue and groove boards, plywood, stucco, metal or vinyl and have little or no function in older homes. These areas are covered to prevent birds or other pests from taking up residence and to provide a proper finish. In newer homes the soffits are perforated or left partially open to the attic above and have vents installed. This allows a good supply of cool fresh air into the attic, which helps with convective currents and removal of warm moist air. This cool air helps the warm air in the attic rise to the vents on the top of the roof and escape. Facilitating the removal of this moist air from the attic will prevent moisture damage to the wooden components and premature deterioration to the roofing.
If the soffits are stuccoed, there is likely little allowance for attic ventilation from this area. Vents may be installed, but there may not be much of an opening between this area and the main part of the attic. If insulation has been added, since original construction, the spaces between the rafters may be partially blocked over the soffit areas. Adding ventilation to this area should only be attempted if there is a current problem with condensation or ice damming on the roof above.
In older homes, attic ventilation is normally easier to add by installing roof or gable vents rather that soffit vents. Depending on the design of the roof structure, added vents in these areas may be adequate and the need for increasing soffit venting not required. In many homes, especially ones with steep pitches or different slopes on the same sections, adding soffit ventilation may help prevent ice damming. This is often accomplished by removing large sections of the wood and stucco.
To check the possibility of adding ventilation through the older soffits, a trip into the attic is necessary. The areas closest to the eaves should be viewed with a flashlight or trouble light to see if there is much of an opening to the outside. If the space near the bottom of the rafters is not blocked by wooden framing between the rafters, soffit vents may be added relatively easily. If the areas over the outside walls are not easily visible by pulling back existing insulation, soffit venting may not be possible. Insulation should be pulled back or slightly compressed so that it does not touch the underside of the roof sheathing. Cardboard or foam air chutes can then be installed between the rafters to prevent the insulation from blocking air movement.
If openings are present at the bottom of the rafters and proper air chutes installed, soffit vents are installed by simply cutting holes in the soffits to accommodate the installation of metal or plastic vents. The most difficult part of this job is cutting through the old stucco, itself. Older stucco is cement-based and can be very hard. It may have to be cut using a special masonry blade on a circular saw or masonry cutter. Once proper sized holes are made in the stucco, the wood underneath can be cut and removed to allow airflow into the soffit. Vents can be installed by fastening to the wooden boards behind the stucco or with anchors into the stucco itself.