It seems problems with windows in new homes are all too common. Zurich Building Guarantees’ annual Customer First Survey of new homebuyers showed that 43.6% of respondents had problems with the windows in their new homes in 2002. Water penetration through the building envelope comes high on the list of defects, with many of these problems being attributed to windows, doors and their openings. Most of these defects could be prevented through correct design and improved workmanship, although the homeowner also has a responsibility in the way they use and maintain their properties. Nick Cuffe, technical manager at Zurich, outlines three of the more common problems and looks at possible solutions.
Q. How do you stop water penetration around a door or window frame?
A.Missing or incorrectly positioned vertical dampproof course or proprietary cavity closer.
Horizontal tray with associated stop ends and weep holes omitted from above the structural opening.
Poor detailing for exposure.
SolutionsMastic sealant is relied on too much and is also used inappropriately to fill excessive gaps around external frames. It is only a secondary measure to prevent water penetration. The structural opening should be formed, avoiding excessive gaps around the frame. Proprietary cavity closers should be used to prevent water ingress and avoid cold bridging at internal reveals.
Moisture build-up within cavities will form on external frames. The installation of horizontal cavity trays will protect the opening from moisture ingress and, in conjunction with weep holes, will allow the moisture to escape from the building envelope. Stop ends, formed at the ends of each horizontal tray, and sufficient coverage of the lintel bearing ends will prevent water tracking down the inner faces of the opening reveals and being drawn back into the building. Some lintels incorporate a cavity tray. However, dependent on the exposure of the building, secondary dampproof trays may still be required.
Insufficient external recess to the reveal and/or windowsill overhang can cause water ingress around a door or window opening. Frames should be set back from the elevation face with overhangs appropriate to the exposure of the building.
Level access detailing of external door frames should not only allow access for disabled people but needs to prevent water from entering the building. Manufactured door thresholds and frames, in addition to specific details, should always be used.
Q. How do you prevent damaged windows and door frames including coatings?
A.Materials are unprotected, not only in storage, but once they are installed.
Specifications for coatings are inappropriate or poorly applied.
Lack of maintenance.
SolutionsAdequately protect frames especially to prevent damage to windowsills and other projections of the frame including the ironmongery. The rigours of construction activities necessitate robust protection methods.
Painting and other coatings should be appropriately specified dependent on the expected exposure, particularly in coastal areas. They should be applied in accordance with the manufacturer’s recommendations and not generally in or immediately before inclement weather.
Pre-finished frames need to be frequently cleaned with non-abrasive cleaning agents. Painted windows should be regularly maintained. Recoating intervals will need to be reduced in exposed areas or aggressive atmospheres.
Q. How do you stop condensation forming on the frame, glass or around internal reveals?
Lack of ventilation
SolutionsUse insulated lintels and proprietary cavity closures to form the structural opening.
It is recommended that only British Standard or equivalent, marked double glazed units are used. A drained rebate is a preferable method for glazing in timber joinery windows.
Mechanical and background ventilation installed in new homes is often inefficient or is not used by the occupier. Trickle ventilators to windows should be opened to alleviate condensation and allow air circulation within the home. Mechanical ventilation, particularly in kitchen and bathrooms, should be used. Extractor fans need to be appropriately sized and installed in accordance with manufacturer’s instructions and ducted to atmosphere preventing condensation build-up – usually on door and window glass.
This article is a summary and not necessarily a comprehensive review of the subject matter. The views expressed in this article are those of the author only and not necessarily those of Zurich Insurance Company.