Thurston Home Talk: Shingle Roof Replacement

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Thurston County Home InspectorSubmitted by: Dwayne Boggs (Dwayne is a home inspector serving the Thurston County area home inspection market)

As a home inspector in the: Olympia, Lacey, Tumwater and greater Thurston County area when it comes to roof questions I always get asked “…can we just put new shingles on top of the old roof…” In general it is not a good idea to overlay a traditional asphalt shingle roof. It is much better to do a complete tear-off and replacement. When you put new on top of old you can’t examine the decking to determine if there is any damage that needs repair.

If you don’t take your roof down to the sheathing, you will never know if you have proper underlayment or potential water damage. The best –case scenario for an overlay is sound decking and no previous or existing leaks, and a roof with no sidewalls where flashing is needed to tie in the roofing material to the exterior walls of the home. However, if you overlay, you cannot install a water- leak barrier, as it has to adhere directly to the wood decking. The second layer is also more difficult to install properly compared to new shingles. Flashing around roof penetrations and sidewalls can be compromised. Plus, depending on the size of your roof, you’ve added multiple tons of weight on the trusses. If there are any pros to overlaying a roof, it’s saving a little bit of money. However, because of the amount of prep work involved in overlaying a roof properly, any saving are usually modest maybe 25 percent compared with full tear off and replacement of a new roof. The shingles likely won’t last as long with an overlay, so the job could actually end up costing you more in the long run. The savings simply do not warrant the compromise of quality and potential risks.

That said, overlaying asphalt shingles with a metal roof could be an option, provided there is no underlying damage. Metal roofs offer energy savings but do cost more upfront than traditional asphalt shingles. They also last longer and stand up to foul weather better than shingles.

No matter what type of roof you choose, make sure you tell your roofer to fix any underlying problems you have before installing any new roof. The bottom line is: Your roof is arguably the most important component of your home – after all, it protects everything under it, so it’s not an area where you want to cut corners.

When weighing the modest savings against the possible uneven appearance, reduced life expectancy, and risk of future leaks — I would advise “against” an overlay with new shingles. Find a high-quality roofing contractor who can assess your roof’s condition and do the job correctly.

 

About the Author

Dwayne is the former past President of the  Washington Association of Property Inspectors, Dwayne is also a committee member for the Washington State Pest Management Association (WSPMA), Dwayne has been serving the Thurston County home inspection markets of Olympia home inspection , Lacey home inspection and Tumwater home inspection for many years. Boggs Inspection Services can be reached at 360-480-9602.

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