Because the rot from leakage will damage the sheeting and anything else it gets to.

What happens to a roof as it ages?

Prolonged Aging





According to expert roofers, deterioration starts on a minute level, with microscopic cracks appearing in the asphalt surface. Other noticeable changes include the loss of a few granules and evaporation of volatiles — compounds that are added to the asphalt to keep shingles waterproof and flexible.

Should I remove my old roof?

We would not recommend a removal unless it was absolutely necessary. Removal of the existing roof may be needed for one of the following reasons: Too many layers of old roofs to allow another roof on top. The exposed shingles are badly warped or buckled and will not provide a smooth enough surface for the new roof.

How bad does a roof have to be replaced?

A reputable roofing contractor will recommend that you replace your roof somewhere around 80-85% of the manufacturer’s life of the roof. For example, you should consider replacing a 25-year roof around the 20-year mark.

Is it better to roof over existing shingles?

While a repair job can often be more convenient and somewhat more cost-efficient, placing new shingles over old ones is never a good idea. Whether repairing one section of roof, or a replacing a whole one, it’s always best to pull up the old shingles before putting down the new ones.

Can you put a new roof over an old one?





Roofing over an existing roof is also called reroofing or an overlay. It is the process where roofers install a new roof over your existing one, i.e. add a new layer of shingles, which means that there is no tearing off of the old roof.

What is the difference between re roof and new roof?

Roof Recover: The process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering. Roof Replacement: The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering.

Can you put new plywood over old on a roof?

As long as the new plywood itself can span the distance and carry the roof, wind, seismic and snow loads for your region, adding new ply over old is just fine. The new plywood thickness should be at least equal to the exusting plywood thickness.