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Wood shingles can provide a durable and attractive roof if the right products are selected, but with the wide assortment of species, styles and grades,
which one is best?
Here I will examine some of the different aspects of the woods used for roofing, the methods of manufacturing the roofing products, and a guide to grading
the shakes or shingles, to ensure that you are getting the best product available.
Selecting the Right Species
Shakes and shingles are made of various
materials, depending on the location.
The most common on the Pacific West Coast is
with some also made from Nootka Cypress (Yellow Cedar).
On the East Coast of North America the most popular species is Swamp Cedar, also known as White Cedar .
In Eastern Europe Pine is sometimes used to make shingles. A few people on the Pacific Coast have also experimented with Hemlock, Fir and Spruce, with mixed results. These products are not available commercially, do not weather well and are generally not manufactured except by custom order.
-White Cedar (Thuja Occidentalis) has the lowest oil and tannin content, and makes the shortest lived of the popular wood roofing materials. It is used mostly
on the East Coast where it is readily available. It is also known as Swamp Cedar. Some people prefer this species due to it's uniform grey color
when it is aged. The grey or white color is the result of the oils being removed , exposing the cellulose or fibrous structures of the wood.
This type of wood generally lasts 10 to 15 years, and up to 25 depending on the grade and style of shingle. Most web sites which compare
roofing products base their evaluation of wood shingles on this species, though it is the worst suited to the application, and not representative of other species.
-Yellow Cedar (Callitropsis Nootkatensis) grows at high elevations, in poor conditions, resulting in slow growth and tight rings. Due to the tight growth
rings it is said to be the strongest of these woods, and is also quite durable, almost equal to Redcedar in its resistance to rot and insects, but not very common.
The trees typically yield little useable wood, are prone to weather damage in intermediate stages of manufacture and the hardness of the wood results in some difficulties in production. Shingles made from Yellow Cedar can last more than 50 years, slightly less than Red cedar and a little more expensive.
-Western Red Cedar (Thuja Plicata)
provides the best raw
materials for roofing, with the most durable shingles.
What Style, Shake or Shingle?
There are two basic types of wood roofing products, shakes and shingles.
The main difference between the two used to be that shakes were split and shingles were sawn, however there are many hybrids
which make the distinction ambiguous.
- Shakes used to be the preferred style of roofing, due to the low waste from splitting blocks into shakes, there was virtually no waste at all, and there
is no machinery required to make them. A man with a hand saw and axe could manufacture high quality hand split shakes, and similar products have even
been made with stone tools by the natives of the Pacific Northwest.
The main drawback is that it requires very high quality wood, not just solid, but straight and with a smooth grain. Any twist or corrugation
would produce a shake with rough edges. This would form a gap between shakes laid on top of each other, which can allow wind driven snow and
rain to penetrate, and the wind can catch on raised edges.
In an effort to make lower quality wood acceptable for shake manufacture several innovations have been incorporated into their manufacture.
They were sometimes planed with a draw knife, a large blade with a handle on each end, to smooth them so they could fit tightly together.
With increased usage of machines in production this was eventually replaced by a band saw. Instead of flipping the block after each shake was split off,
which forms a tapered shake known as a hand-split, the blanks or un-tapered shakes were split off one end, the flat board was then run through a band saw
by hand, from corner to corner, forming two tapered shakes, each sawn on one edge. This is known as a re-sawn shake.
Any twist or roughness was still present, but confined to just the one side which was not sawn. Though this reduces the size and number of gaps it does not
totally eliminate them, so rough wood still requires a membrane between each course of shakes, and would leave gaps which can catch wind and weaken the roof.
Occasionally an un-tapered shake is used with no further refinement, known as a barn shake or heavies, depending on the length.
The drawback with all of these is the rough edges or twist which can be left on either one or both sides depending on the process and variations in thicknesses.
If careful attention is paid to quality control the shake is a very durable form of wood roofing.
With proper selection of wood and sorting it into the proper categories of shake and shingle grain this is not a problem, but with lax and uncaring workers,
or those trying to make extra money by selling shingle wood as shake, it is a major concern, so much so that the cedar Shake and Shingle Bureau has made
different guidelines for the installation of shake and shingle.
The benefits of splitting the shakes is low waste, with no sawdust from a saw, another factor is that the face is always split parallel to the grain, there are no grain
ends exposed in the face, there is no slash grain or weak shakes from cross grain. The shake is typically longer, also, hence a larger exposure
to the weather making application a bit faster, assuming the average width is of sufficient size. This is often not the case since even a very slight twist over the 24
inch length is compounded by the width of the shake, it is rare to find a shake more than 12 inches in width without some twist, larger shakes are frequently split in
half to reduce this deflection.
Even with an underlying membrane to prevent penetration another concern for the rough surfaces is the uneven distribution of pressure on the shakes. If a shake
lies on top of a high point like a fulcrum it can shift, loosening fasteners, it can also be split as it flexes over it under load.
Shakes made from shake wood, that is logs with straight grain, are fantastic, fast to cut and apply, with little waste. Shakes made form shingle grained wood are
very poor, and I wish people would stop making them.
-Shingles are sawn on all six edges. With increased mechanization in wood harvesting the development of a large circular saw and carriage to automatically
feed the wood into the saw drastically changed the possibilities for manufacture.
Rather than pushing twisted or rough wood and making a low quality shake, the wood could be sawn with the circular saw, forming
a smooth and straight shingle with uniform thicknesses. There is a lot more waste during the processing, but if the extra retention from the harvesting is considered
there is actually better recovery with shingle. When the shake blocks are harvested a good cutter trims off a lot of wood and leaves it in the bush. When splitting
shingle blocks the cutter can harvest trees with more twist, corrugation and other defects, plus the good quality trees which could make shake always have some
knots or burls which would have to be trimmed out. Not just the defect, but a lot of wood on either side of the defect which is curved around it. All of this
wood is recovered by shingle manufacture.
Like shake manufacture, shingle processing also requires attention to quality control. With the saws ability to cut off-grain a lazy or incompetent worker could
make shingles which do not follow the natural grain of the wood, exposing end grain in the face, cross grain and other defects which can weaken a shingle or
make it so that it does not last as long in the weather.
For this reason grading and licensing agencies have had to be created, to supervise production and ensure that all of the shakes and shingles reaching the consumer
are of good enough quality to be used on a roof.
Of the two, shingles are much easier to maintain a uniform thickness, straight and smooth face, making them fit together much more tightly when applied on a roof.
Due to the way the shingles are manufactured it is possible to have shingles up to 20 inches wide with no curve, twist or any other kind of defect. This offsets the extra coverage and speed of the shake roof application, if there are good splitters making the blocks which are to be processed.
It is frequent for lazy splitters and loaders, both for shake and shingle, to split the blocks smaller, to make them more manageable for lifting by hand. This produces
an inferior product, with smaller sizes and lower recovery.
Another concern is the lack of maintenance for the saws cutting the shingles. If the saw is not set up correctly and maintained it can also produce rough shingles,
differing in form from the roughness of shake, though. Instead of being smooth on one end where a shake is split, with gradually increasing valleys and ridges
toward the other end, with a shingle saw cutting rough it forms semicircular grooves in the face of the shingle, and can even bend the saw so that it dives in to the
block, making the butt of a shingle too thick on one side, and the next shingle will have a tip which is too thin.
Though shingles are thinner than shakes, they are actually just as resistant to wind and hail, due to the tight fit and intimate contact with the underlying shingle and
roof structures, support is uniformly distributed, there are no high spots over which the shingle will bend or split. There is also less of the shingle
exposed, so less leverage for prying it up. Shingles are applied with enough overlap to have three layers at any given point, whereas shakes have a two layer coverage.
Hybrids: There are a few products which are classified as shakes, but manufactured in the same way as shingles. These are Taper-sawn shakes, which
can be sawn on all six sides just like a regular shingle. The difference lies only in the thickness of the butt of the shake, which is 5/8" (0.625") instead of 0.45"
for a regular shingle.
With the robust dimensions of the shake, which allow for increased exposure, along with the uniform thicknesses and smooth surfaces from shingle saws allowing wider boards there is faster application with fewer pieces of wood to cover an area.
Conclusion:
For both shake and shingle the main factor is not the style of production, but the conscientious application of grading rules
and common sense of the manufacturer.
A shingle made by a lax worker is inferior to a shake made by a good worker, whereas a shake can be inferior to a shingle if the workers switched.
There is no superiority of one product over the other, except in the reputation of the one making them. Rough wood should be culled and sent to shingle
manufacture, rather than making poor quality shake, and shingles should be made with the same care and attention to quality.
The only real differences lie in the cost, shingles can be made from poorer quality raw materials, yet have equal or even superior finished products. The workers
in the bush can produce more wood in the same type of area when cutting shingle, increasing productivity, decreasing crew movements and tenure applications,
The shingles can be made faster and easier, so the end result is a decrease in the cost of the finished product. If both shake and shingle can be equal in every
aspect, but the shingle is cheaper, then it is, of course, the preferred material.
To me there are three ideal products
-Hand-split shakes, due to the very low waste and having little need of machinery to produce them, they require very high quality materials, straight
grained wood with no twist or defect. Standard length of 24". Thicknesses of 3/8", 1/2" or 3/4".
-Tapersawn shakes, with good characteristics of both the shake and shingle, able to be produced with sub-grade logs not suitable for hand-split,
but with a finished product of similar quality. This has the robust dimensions of shake but smooth sawn surfaces like a shingle. Standard length of 18", thicknesses of 5/8" or 3/4".
-Perfections, or shingles cut with a length of 18" and a butt thickness of 5/2.25" (five shingles stacked add up to 2.25") Three layer application eliminates need for felt interleaving.
What Grade?
Roofing shingles come in four grades, 1, 2, 3 and 4.
#1 grade or Blue Lable. There is no flat grain, knots, cross grain, sap wood or any other imperfections in any part of the shingle.
#2 may be flat grain, may have some sap wood and may have an imperfection in the tip of the shingle.
#3 may have all of the imperfections as a 2, but more sap wood, and imperfections in the middle third of the shingle.
#4 must be solid on the butt. the rest of the shingle may be entirely defective. It is to be used only for under-courses, not suitable for roofing application.
|
RED CEDAR 18”
PERFECTION SHINGLES |
No.1 Grade |
No.2 Grade Red Label |
No.3 Grade Black
Label |
No.4 Grade Green
Label |
|
|
WOOD: |
Clear Area |
All |
11” |
6” |
Butts Sound |
|
|
Sapwood |
None |
1” |
Yes |
Yes |
|
|
Flat Grain |
None |
Yes |
Yes |
Yes |
|
|
Checks/Cracks |
None |
2” (to
16”) |
2” (to
16”) |
Yes |
|
|
Defect Size |
None |
3” |
3” |
3” |
|
|
Total Defect |
None |
½ width |
2/3 width |
No Limit |
|
LENGTH: |
Maximum |
None |
None |
None |
None |
|
|
Minimum |
17” |
16” |
16” |
14” |
|
|
Exposure Line |
5 ½” |
4 ½”
|
4” |
n/a |
|
WIDTH: |
Maximum |
None |
None |
None |
None |
|
|
Minimum |
4” |
4” |
4” |
2 ½” |
|
|
Undersize % |
10% |
20% |
30% |
No limit |
|
|
Min. Undersize |
3” |
3” |
3” |
No limit |
|
|
Off Parallel/Square |
¼” |
3/8” |
3/8” |
3/8” |
|
THICKNESS: |
5 butts, measured
together to equal 2 ¼” |
||||
|
COVERAGE: |
4 bundles per square |
635 lineal inches on
grade per bundle |
|||
|
PACK: |
18" wide frame |
20/20 pack |
|||
|
|
20" wide frame |
18/18 pack |
|||
To have a wood roof last to the extreme of it's projected life term careful grading must be done. Many mills push the limits of grading, putting as many 2s and 3s
in with the ones as they can get away with while still passing inspections. Every one of the sub-grade shingles will shorten the life expectancy of the roof and should be removed by the one applying them to the roof.
It is also common for buyers to select a lower grade, trying to save money; after all, for each grade reduction the price is generally cut in half. The life expectancy of the materials, however, is not cut in half, but quartered. This means you might apply #2s to the roof for half the cost, instead of getting 100 years it is reduced to just 25 in optimal conditions, and if conditions are poor, even less.
This doubles the cost/year amortization of the roof application, so in the long run you will spend more, by as much as double, plus the extra work of actually going up on the roof and replacing it in 20 years, when it should have been your kids replacing it sometime near their retirement age.
The extra cost of getting good quality materials far surpasses the value of the money. For roofing applications only #1 perfections should be used, and if the mill you bought them from includes culls in their perfections, discard them, use them for under-courses or return the merchandise for a refund, do not accept inferior products because you will be the one who pays for it in the end.
Disregard any statement made by a seller that "all sales are final", because when there is a #2, 3 or 4 in the mix, then you didn't get what you paid for and any disclaimer made by the seller is void due to their misrepresentation of the materials. If they are selling #1s, they should be 1's in the bundle, right?
It is important for the mills to know and follow grading rules, but it is also required for roofers to know these rules too, and it is a very good idea if the buyer, the owner of the house, familiarizes themselves with the grading rules.
This will insure that inferior products are not accepted in the industry, and those mills that do not presently try to exceed the standard will either have to conform
or go out of business.
With the present market conditions there is already a clear distinction between the mills that make a good quality product, and those that do not.
Most of the mills that have poor quality are closed, some have not been working for 1 1/2 years or more, several have two to three million dollars in stock in
the yards, and noone is buying it, because for the same price you can now get the high quality shakes and shingles.
The reason for grading rules is the protection of the buyer.
The problem with lower grades, for example, flat grain, is that it can cup and split, due to the tension within the shingle from the grains shrinking. The grains on one side are much longer than the other, and since the wood shrinks along these grains the difference in length causes a difference in shrinkage, causing one side to pulled more than the other. Eventually this cupping will cause the shingle to split in half. If there is a joint under this split, then 2 of your 3 layers of protection have failed. if there is actually a 3 or 4 ( with a defect in the middle or butt) under that, or another split shingle, your roof may leak.
Conclusion:
Both shake and shingle in any style can provide a very durable roof, the key factor is having a reputable manufacturer.
Having a good worker make both, the shingle is cheaper, and with large widths can offset the high exposure of shakes.
The shingles, also, are easier to produce, so less skill is required and on average the quality is more consistent than shake. There is more
demand for shake and a higher price, so there is more pressure for workers to include sub-grade materials.
In my opinion the best product for all-round performance in price, longevity, weight and ease of installation is the Western Redcedar premium grade Tapersawn Shakes, 18" lengths and 5/8" butt thickness, followed closely by #1 grade shingles (perfections, 18" X 0.45" (5/21/4")),
especially if the width of the shingles is above average, and if, and only if, there is a reputable supplier that has a good supply of high quality shake wood, and conscientiously culls corrugated or twisted wood, then hand-split shakes are an excellent product. the best option for hand-split shakes is to actually do it yourself, since few others will care as much about quality as the one putting their own roof up, of course not everybody can take the time to do it, so go to the mill or warehouse, actually look at the product before buying, learn about it and make sure you are getting what you need.
Wikipedia,
the free encyclopedia