Can new asphalt shingles be laid over old shingles?

When their asphalt shingle covered roof has reached the end of its life, most people assume their only option is to strip down even the siding before a new roof can be applied. But unless the siding is badly damaged or the structure cannot support the weight of another layer of asphalt shingles, a better solution is to apply a new layer of asphalt shingle just over the old asphalt shingles. Done right, a reroofing job will look as good and last as long as a "new" roof, for a lot less money and a lot less hassle.

However, if done badly, it may lead to costly roof repairs. Checkout how you can repair roof in one of my fantastic post here. 

Installing a new layer of asphalt shingles will give your roof depth and even a three-dimensional appearance, as it is slightly raised due to the existing asphalt shingle layer underneath. 

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INSTALLATION

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Starting with a modified starter course, remove the tabs from a three-tab asphalt shingle and just enough from the top of the starter course so that the remaining portion is equal in width to the exposure of the old asphalt shingles.

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Lay starter course to be even with existing roof to eaves by applying factory adhesive along edge of eaves, remove 4 inches from end of first starter course to ensure joints between adjacent starter courses they will be covered by the time you apply the first course of asphalt shingles.

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For the first course you need to trim enough material from the bottom of the asphalt shingles to fit snugly between the bottom of the tabs of the previous third course and the eaves edge of the new starter strip.

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Start with a full asphalt shingle, use four nails per shingle placed according to the installation instructions of the respective asphalt shingle, in this case if you apply Cambridge, it would be in the nailing line. Use slightly longer nails to penetrate the old shingles and wood roof deck. For the second and subsequent courses, stagger the asphalt shingles as if you were laying a new roof deck.

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Place the top edge of the new shingle against the bottom edge of the tabs of the old shingle from the top course, although this method reduces the exposure of the first course, this will not be noticeable from the floor.

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For valleys, you must first fill the exposed valley area with roofast to the level of the old asphalt shingles, center a minimum 28 gauge 24-inch wide precast galvanized valley sheet metal at the apex and nail it into the edges only with the necessary nails to keep it in place.

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Pay close attention if you work with existing flanges or flashing. If existing flashing is in good condition, continue to apply new shingles over existing shingles, trim new shingles ¼ inch from existing liner, embed last 3 inches of shingles in plastic asphalt cement.

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If flashing replacement is necessary, remove top flashing, cut old shingles covering shields and flashing, backfill exposed roof deck areas to smooth surface using old asphalt shingles before applying shields or flanches.

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When applying the new asphalt shingles each course will be covered by a flange protector, the flashing needs to be a minimum of 5 inches high and 5 inches wide, each flashing must overlap the one underneath at least 3 inches, but should not be visible underneath. the top layer of new asphalt shingles. Consider swapping out old metal flashing for new ones.

Complicated? Hope not! I have more interesting roof posts coming right up. So, pay a visit to my roof blog more!