In
construction, capping or window capping (window cladding, window wrapping) refers to the application of aluminum or vinyl sheeting cut and formed with a
brake
A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction.
Background ...
to fit over the exterior, wood trim of a building. The aluminum is intended to make aging trim with peeling paint look better, reduce future paint maintenance, and provide a
weather-proof
Weatherization (American English) or weatherproofing ( British English) is the practice of protecting a building and its interior from the elements, particularly from sunlight, precipitation, and wind, and of modifying a building to reduce ...
layer to control the
infiltration of water.
[Gibson, Greg. ''Remodel!: an architect's advice on home renovation''. New York: J. Wiley, 1996. 269. Print.]
Overview
The capping application must direct water away from the original under-lying wood material and prevent infiltration of water into the structure. Cladding applied to exterior window and door casing (brick-moulding) and their associated parts is often referred to as ''window capping'' or ''window cladding''. This sort of capping is typically applied in order to eliminate the need to re-paint wood window trim. The
aluminum capping helps to prevent
wood rot by protecting the wood from water and snow. However, capping will exacerbate wood rot if the moisture in the wood is coming from inside the building or the capping leaks. Good installation of capping allows for an outlet for water in the event of a leak.
Caulking and
sealant materials may be used to help prevent leaks but these products are not considered reliable in the long-term.
A
sill
Sill may refer to:
* Sill (dock), a weir at the low water mark retaining water within a dock
* Sill (geology), a subhorizontal sheet intrusion of molten or solidified magma
* Sill (geostatistics)
* Sill (river), a river in Austria
* Sill plate, a ...
that has been clad should provide a "drip cap" or "drip-control" function. This will serve to direct water away from the wall surface directly underneath the sill. The leading edge of the sill must be the lowest point on the sill to ensure that water does not wick into the sill material.
Window capping may provide a marginal increase in
energy efficiency by decreasing the potential for drafts by providing an extra barrier between the exterior and the interior.
The most common material used in residential window capping is factory painted aluminum. An alternative to factory painted aluminum is to use a vinyl coated aluminium material.
Aluminum capping can be painted so long as the painter is highly skilled and knowledgeable in the field of metal painting.
Criticisms
Capping can hide problems rather than fix them. Aluminum and vinyl are impermeable materials so the natural transfer of moisture through the wood trim will be trapped when it reaches the capping material. The quality of paint on some aluminum coil stock begins to chalk or fade in about five years so the claim of being maintenance free can be misleading.
References
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Building engineering