In the Rain, It’s What’s on Top That Counts
The crowning glory of an old-house restoration is a new roof of wood shakes or shingles.
The standard roofing material of Colonial times continues to be used today in many parts of the country. Originally, the type of wood used was dependent on what was available locally.
For example, red cedar was plentiful on the West Coast, swamp cedar in the mid-Atlantic states, white cedar in New England and cypress in the South.
Today you’ll still find a variety of woods used to make wood shakes or shingles, such as red and white cedar, white pine and oak.
If it’s installed and maintained properly, you can expect a wood roof to last a long time. Although 25 to 30 years is a good minimum, some are known to still be functioning properly after 70 years.
Understanding what’s involved for installation and maintenance will go a long way in helping determine if a wood shake or shingle roof is the right choice for you.
One of the secrets of a successful wood-roof application is adequate ventilation. Because of the nature of the product, air must be able to circulate underneath it to prevent moisture buildup and its resultant rot.
Historically, an open-sheathed roofing system was used, which accomplished this objective very nicely.
Today, this is still the preferred method of installation. But keep in mind that the rough, uneven nature of shakes demands some extra protection.
When installing shakes, the open sheathing should be interwoven with the felt paper so the tips of the shakes are up underneath the felt. This provides extra protection from driving winds and rain but still allows adequate ventilation.
The felt paper interweave is usually not necessary with shingles, because they lie flat. If an open-sheathed roof isn’t a practical option, the shakes or shingles should be attached to horizontal furring strips that allow an inch or so of air to move between the bottom of the shingles or shakes and the plywood or solid sheathing.
Another important factor is allowing for the natural expansion of wood. If space is not left for this and the shingles or shakes are butted up close together, you’re likely to get a failure, or crack, in the nail line.
Usually, leaving a quarter-inch space or keyway between each shingle, and about a half-inch space between shakes is enough to allow for any movement.
When actually fastening shingles, the shingle, ideally, should hang on its nails. The nailheads should be driven so they are just flush with the shingle surface. Don’t dimple it or sink the nails in, as you run the risk of punching a hole which will allow the shingle to lift right off the roof.
Two nails should be used per piece, placed about three-quarters-inch from each side, an inch above where the next butt line for the next row will be. Covering the nailheads like this helps prevent them from rusting and staining the roof surface. The seams should line up for three courses, preventing water from wearing a channel or path in the roof.
Always check local building codes before re-roofing.