When Should I Change My Asphalt Roof?

The most obvious time to change your roofing material is when it begins to leak…but that’s not always true. I use this 4 stage method when performing a roof inspection. The roof’s life span can be shortened by several factors, including (but certainly not limited to) poor attic ventilation, hail damage, and poorly manufactured roofing material.


Surface granules begin to wear away, leaving discolored, blotchy patches that are easy to see on a light-colored roof…check downspout outlets where piles of granules collect. Granule loss exposes the asphalt to direct sunlight, making the tab sections brittle and more likely to break off. This is usually a good time to re-roof by simply covering the existing roof with a new layer.

NOTE: Take care not to cover the roof with more than two layers. Some local codes do not allow two layers; check with your local code official(s). Also – keep in mind that double layering (roof-over) will most likely void the new shingle warranty. You should also consider the extra weight added to the roof bracing – called “added dead load.”


Bare spots increase in number and enlarge in size, and a few of the most exposed tabs may start to curl (you can see this happening on the edge of the tab)…you’ll need to re-roof sooner than later.


The brittle tabs curl more and crack, and you’ll find chunks of shingles on the ground and in gutters…water can leak in through exposed nail heads at this stage. You can still re-roof (just barely) but only after replacing the broken and brittle tabs.


More tabs have broken off, and most shingles are curled and brittle; repair gives way to replacement. You must start from scratch, strip the roof to the decking, and come in with new felt and shingles.


Measure your “under roof area” (the square footage estimate should include all porches and your garage) and multiply the total footage by 1.3 (use a slightly higher number for steeper roofs, over 8/12 pitch), and add 10% for waste. Divide that number by 100 for the total number of squares to purchase. Then multiply that number by 140 to 160 for a tear-off and replacement. (a lower number for a simple nail-over).

2021 prices in the central Mississippi market.

The calculation won’t be exact, but you won’t miss it far. Example. Let’s say your total footage (heated area + garage + storage room+ porches) equals 2,500 sq ft. Multiply 2500 x 1.3 = 3250 + 320 (10% waste) = 3,575/100 = 35.75 square of roofing material. Round that number to 36 square and multiply by your labor and material cost.

The above tips are used to inspect standard 20-year, 3-tab asphalt shingles. Check with your local jurisdiction for the potential need to purchase roof replacement permits. Contact me for more construction consulting advice and tips. Care should be taken before climbing on any roof surface.

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