Q: We want to buy a 1980s-era home that has cedar shingles. I have asked several roofers for a price to repair the shingles but every one of them said they will have to replace the shingles and add new underlayment. It’s like they are all talking to each other. Is it true the shingles need to be removed?
A: Hand-split cedar shingles have been used as roofing for hundreds of years. They were usually split from knot-free logs and smoothed by hand. Because the split wood varied in size and thickness, each shingle was planed as it was installed. Older damaged hand-split shakes can be replaced with a similar type of wood.
In the 1980s, as I remember it, cedar shakes were usually machine split or sawed, and therefore each shingle was more uniform than most hand split shingles. This new uniformly cut shingle did not require the additional task of hand dressing of each shingle’s face.
Because the sawed shingle face is untreated, it can absorb more water than the older hand-split shingles and tend to cup or warp over time. If you are considering replacing the cedar shakes with a standard asphalt shingle, it would probably be less costly than trying to remove and replace individual shakes over the entire roof area.
If the roofer wants to add underlayment, it is because the cedar shakes are attached to a piece of lath or a single board. The lath is not designed to carry the weight of an asphalt shingle, and it will be necessary to add 4-foot by 8-foot sheets of plywood or OSB (orientated strand board) underlayment on top of the wood lath after the cedar shakes have all been removed.