Roof Trim

There are many types of roof trim in use today. First there is rake board trim, which acts as an overhang along the sides of the pitched section of the roof (A – frame). Rake trim in its most basic form can consist of one piece of 3/4″ pine, poplar, or composite material which is padded out with a piece of strapping to create space for the sidewall coverage. In some places and on higher end homes the rake may be much more elaborate, including a frieze board, soffit, fascia and crown molding.

The rake board trim acts not only as coverage for the top of the sidewall, but as a starting point for the roof shingles. The rake is generally covered with aluminum L channel which creates a straight line where each course of roof shingle is started.

Another type of roof trim is the detail which covers what is known as the bird’s mouth. The bird’s mouth is the end of the rafter tails that overhang the exterior walls. This section of roof trim is usually tied into the corner boards and most commonly consists of a frieze board, soffit, fascia and bed molding. There are also many ways to create fancier details such as adding dental and crown molding.

Where the rake trim, bird’s mouth trim and corner boards meet there is an additional piece of roof trim known as an ear board. This piece is a triangle shaped board that is nailed to the ends of the bird’s mouth soffit and fascia in order to keep the look of the rake board uniform with the rest of the roof trim.

In the same vein as the rake, the bird’s mouth trim is also a meeting point between sidewall and roof shingles. The sidewall generally butts up to the frieze or soffit while the fascia acts as a starting point for the roof shingles. Unlike the aluminum L channel that is applied to the rake trim, aluminum known as starter vent is generally used on fascia trim. Although in some applications the soffit has venting, in which case the traditional L channel is used.

The starter vent at the soffit (or fascia) is a critical element. It allows air to flow up through each rafter bay to the peak of the roof where it is allowed to escape through what is known as ridge vent. Ridge vent is a rolled out mesh or composite material that is covered with shingle caps.

Traditionally most roof trim has been 1″x8″ # 2 or clear pine. This has been replaced in many circumstances by rough sawn 1″x8″ that is subsequently covered with sheet aluminum or vinyl. Aluminum and vinyl are cost effective ways to avoid painting, maintaining and eventually replacing roof trim.

In recent years some high end houses have veered towards products like Azec, which is a solid composite 1″x8″ stock that looks much like traditional trim from a distance but has the long lasting, no maintenance qualities of Aluminum and Vinyl. Unfortunately its very high price leaves in un-available to many.

Roof trim is very different in many parts of the country, but the one universal certainty is that technological advances are playing a major role in the materials we use to trim our roofs.