Can I put plywood over old roof?

The new plywood will have to be nailed to the rafters or roof trusses. … But, with the old plywood left in place, it will be considerably more difficult to locate the rafters to ensure proper nail placement.

Is it OK to put a new roof over an old one?

The answer is yes, you can lay new roof shingles over old ones. … You can’t do it with wood or slate, for example, and you should never mix materials, such as laying asphalt shingles over cedar shakes. Also, the old roofing has to be in pretty good condition.

Do you have to replace plywood when replacing roof?

If you are getting a new roof, while you may not necessarily need to have the plywood decking replaced, you should have it carefully inspected by a qualified roofing contractor. … When considering a contractor for your project, be sure to address the subject of plywood replacement, and what the cost per plank will be.

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How much does it cost to replace a roof including plywood?

The thicker the plywood your roofer uses, the more expensive the job will be. Your price could vary depending on how much the roofing company charges for labor, but generally, you can expect to spend between $70 to $100 for each sheet of plywood.

How long does plywood last on a roof?

There are a few averages you can expect, but they are dependent on these factors. Plywood siding, such as T-111 should give at least a 35 year life expectancy, if finished properly; but there are many cases of it lasting over 50 years. Roof sheathing should last 30 to 40 years or to put it another way, two roofs.

Should I tear off my old roof?

In most cases, more than two layers of roofing shingles does require a tear-off. Laying new shingles over old shingles is easily prone to leaks and reduces the life of the new shingles. This alone ought to be reason enough to do a tear-off; it’s just a bad value not to.

Is it better to remove old 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.

How do you fix rotted plywood on a roof?

How to Replace Rotted Roof Decking

  1. Step One: Estimate the extent of the damage. …
  2. Step Two: Remove the roofing. …
  3. Step Three: Measure the area. …
  4. Step Four: Cut out rotted wood. …
  5. Step Five: Cut the replacement decking to fit. …
  6. Step Six: Position the replacement. …
  7. Step Seven: Secure the decking.
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How long do a roof last on a house?

Your asphalt roof is about 20 years old

For a standard 3-tab asphalt shingle roof, that’s 25-years. As long as your roof has been properly ventilated and installed you should get pretty close to that 25 years of roof life.

Which plywood is best for roofing?

Exterior Plywood is the preferred material for roofing. It also performs well when exposed to moisture over long periods of time. The price is low compared to other roofing materials and the installations are also easy.

How thick is plywood on a roof?

Most roofs will be sheathed in plywood at least 3/8 inch thick. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. Loads will vary with the pitch of the roof; the flatter the roof, the greater the load on any one section. Steeper roofs will have lighter loads per square foot.

How many sheets of plywood do you need for a roof?

Divide the total roof area by 32 to get the number of sheets you will need to cover the roof. A typical 4 foot by 8 foot sheet of plywood covers 32 square feet. If your roof area is 1,600 square feet, 1,600 divided by 32 will mean you need about 50 sheets to cover the roof.

Does plywood go bad?

Plywood does not have an expiration date.

Can you roof over wet plywood?

A: It is never a good idea to install a roof over wet plywood or any type of roof sheathing. Trapped water will boil when the sun heats the roof and the shingles will then have small pits where the steam finally escapes.

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Will plywood last outside?

Exterior plywood is weather (and water) resistant, so it’s strong enough to be used outside and also in areas that are exposed to water and humidity, like a garage. This type of plywood, often made from Douglas fir, is made stronger by adhering its layers with a waterproof glue.