Installing A Second Layer

   Installing a second layer of shingles over an existing layer of shingles may seem like a way to save money but we believe this method of re-roofing can have some unexpected pitfalls.  Layovers as they are called in the industry involve nesting the new shingles up against the old existing roofing on your home.  Since the new shingles are installed directly over the old roofing you do not receive many items associated with a complete re-roofing job involving removal of the old worn out roofing.

         Removal of old worn out roofing allows your roofing contractor to do a top side inspection of  your roofs sheathing.  This inspection will look for deterioration such as rot, insect infestation, mold, mildew and structural damage to the sheathing.  Removing the old roofing will also allow your contractor to install snow and ice shield on all eaves and in all valleys under your new roofing. Since snow and ice shield is applied directly to your roofs bare sheathing this is something that can’t be installed on a layover where you don’t remove the old roofing. 

        Many times old flashing located under the original layer of shingles can not be inspected or replaced during a lay over roofing job.  Look at your roof does it have more than one roof plane?  Are parts of these roofs surrounded by siding for instance a garage roof that ties into your main house with siding on the wall above the garage roof?  If so and you elect to do a layover here are a few points you may not be aware of. 

        When your home was build your builder installed the siding after the roof was installed.  This allowed the siding contractor to cover the roof flashing on the roof with siding material to make a water tight seal.   Herein lies the problem.  Many times during a layover where the new roofing meets an area of siding such as described above your roofer can not install new roof flashing.  In addition they can not reuse the existing flashing since the original flashing is woven between the original layer of shingles and behind the siding. This leaves your roofer two options either seal the existing flashing or try and pry the siding loose enough to force new flashing behind it.  Both of these in our opinion are unacceptable. 

        Sealing the existing wall flashing most often can be translated as caulk existing wall flashing.  Not only does this rely on caulking for your flashing system it can look unacceptable.  The second option of trying to pry open the siding enough to slip new flashing in also can create problems.  This can leave you looking forward to a future siding repair when the siding comes loose where it was pried open.  With vinyl siding a vinyl J-channel is actually laying on top of the old roof.  Trying to slip new flashing under this j-channel can also lead to problems in the future. 

        We have seen short cut down flashing wedged under this channel in an effort to flash a layover job. The flashing was cut down because of  the siding J-channel nails do not allow for a proper installation of step flashing.  This method once again in our opinion is unacceptable.  Flashing is designed to be certain lengths and widths to prevent water from jumping or running over the flashing during heavy storms.  Cutting down this flashing may lead to future problems and water leaks.

        One final note on layovers.  Your finished layover roof appearance has a lot to do with the condition of your old roofing.  Over time your old roof can start to telegraph through to the new roof as it lays down over time.  These are just some of the reasons Maryland Shingle will not compromise and install any layover roofing over old worn out shingles regardless if your county and state code allow it. Maryland Shingle Roofing & Siding Contractors our quality name is on every roof we do and that says a lot.

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Elkridge, MD 21075-6103

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