Homeownership comes with a hidden bonus: a lifetime of questions you ask yourself about your house. “How long will the hot water tank last?” “How can I find a good electrician?” “Can I reroof over existing shingles?” Your local, friendly residential roofer may not have much to say about the first two questions, but we can definitely help with that last one.

Reroofing Versus Replacement

In the roofing trade, “reroofing” generally means applying a new roof over an old roof. For commercial roofing, this is often an economical, environmentally sensitive solution.

“Full roof replacement” is the correct term for removing an old roof (a process called tear-off) and putting down a complete, brand new roof in whatever material you choose.

Commercial roofs are many times larger than residential roofs, so keeping the old roof in place saves long hours of intense labor, many cubic feet of landfill, and thousands of dollars in material and labor costs.

Do those same savings transfer to residential roofs? Usually not, for several reasons:

While some local building codes allow for two roofs on one home, most municipal codes forbid it.
Commercial roofs are nearly universally low-slope roofs that pitch (slope) very slightly to allow for drainage. This type of roof is very easy for experienced roofers to work on and maintain a fast pace, so every hour saved is serious money saved.
Residential roofs are nearly universally steep-slope roofs, with very high pitches that make all roofing work a challenge. You gain no major benefits in time and labor from avoiding tear-off.
The amount of debris from tearing off an old residential roof is very small and adds little to a landfill. Some of the old roof may even be recyclable.
A roofer may charge only slightly less for roofing over an existing roof versus full roof replacement, since the work is essentially the same (tear-off usually takes only a couple of hours).
Most roofing material warranties are voided if the material is installed over an old roof.

1 Pro

To be completely fair, we can cite one positive benefit of having a new shingle roof installed over an old shingle roof:

However modest, you will see some savings on labor and time with reroofing versus full roof replacement

Only you and your roofer can decide if this one pro in your list of pros and cons outweighs the many cons. If you have reroofing in mind, you may be challenged to find a roofer willing to take your project. Most roofers prefer to perform a full roof replacement:

Inspect and assess the existing roof, including rafters (or trusses), sheathing, and vents.
Remove old shingles, underlayment, defective or corroded flashing, and degraded rubber boots.
Cart away the old roof debris (or recycle as appropriate).
Peel away the old water and ice shield.
Evaluate and replace damaged sheathing.
Lay down fresh underlayment.
Unroll self-adhesive water and ice shield along the lower edge of your roof and in valleys.
Install new starter shingles in cut, color and style of your choice.
Install matching field shingles.
Install matching ridge vents and shingles.
Install flashing, rubber boots, drip edge, and caulking as needed.
Inspect the new roof.

It sounds like a lot of work, and it is. But highly trained roofing crews perform this work every day, year-round. They do the work efficiently, quickly, and well. They preserve the roofing manufacturer’s warranty to protect you, the homeowner.

3 Cons

Imagine a doctor who only puts a bandage over a wound without ever treating the wound. That is roughly what a new shingle roof does in going down over an old shingle roof. Consider these three reasons not to put a new roof over an old one:

Hidden damage — Any issues with the old roof are covered over without being resolved. How will a roofer reach future leaks, corroded flashing, or degraded shingles of the old roof?
Weight — One square (100 square feet or 3 shingle bundles) of new shingles can weigh anywhere from 150 to 240 pounds, depending on the quality and thickness of the shingle you select. All that added weight can severely damage your Indianapolis-area home’s roof, sheathing, and rafters.
Telegraphing — When a thin layer of any material goes over an older material, all the lines, dips and ridges of the old material telegraph, or show through, the new layer. On a shingle roof, this is a terrible look that eats away at home value and curb appeal.

Work with a roofer you can trust and ask critical questions about the good and bad points to reroofing versus full roof replacement. Your roofer will provide expert, unbiased guidance to save you time, money, and embarrassment. Please contact us today at Moss Roofing. We look forward to answering all your questions about your Indianapolis-area home’s roof. We provide a complete range of roofing, siding, gutter and insulation services.