Composition Shingles over Wood Shingles

Comp over Wood


With a few exceptions, wood shingle roofing is prohibited in most municipalities and few insurance companies will insure a wood shingle roof.  When replacing old wood shingles with composition shingles, there is a initial additional expense of installing new decking because wood shingle roofs had slats spaced apart to allow the shingles to dry out more quickly rather than decking.  Some people make the poor decision to skip this additional cost and install the new compositin shingles directly on top of the old deteriorated wood shingles.  This is one of those poorly thought out choices where trying to go cheap ends up costing you much more money in the long run.  The rough surface of the old roof stresses the new shingles almost immediately and they wear out much faster.   Fasteners do not have a good surface to anchor them, so the new shingles are loose and prone to shift and leak.  Of course, any warranties are automatically voided.  The only solution is to admit your mistake and scrape off all of the shingles, old and new and start again with new decking and properly installed roofing material. 

If you look up in the attic and all you see are wood shingles rather than decking above the roof rafters, roof replacement is likely in the near future.  There are exceptions to this.  Sometimes, the roof structure has been reconfigured often to occomodate an addition of some kind.  In those cases, the newly reconfigured roof has been decked and installed appropriately but there might be remnants of the old wood shingle roof in the attic where it is no longer exposed to the elements.  If you are looking up in the attic and you see some areas with wood shingles and some areas with plywood decking, this is probably what you are seeing.  To be prudent, if there is any signs of old wood shingles present, further evaluation by a licensed home inspector or reputable roofing company is recommended.

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