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HomeTrendingCan You Put New Plywood Over Old On A Roof

Can You Put New Plywood Over Old On A Roof

What Causes Roof Decking To Rot

How to Install New Sheathing Over Old Spaced Sheathing for Re-roof Projects

Unfortunately, the trouble with roofs is that issues arent usually obvious from the ground. In most cases, your roofer must get up on your roof and tear off your shingles to fully diagnose the problem. The number-one issue uncovered by roofers during a tear-off is plywood sheathing that is rotted or soft.

Water is your roofs main enemy and since roof decking is made out of plywood or plywood composites, it is especially susceptible to water damage and rot when its exposed to excess moisture for a prolonged period of time. Whether its old and worn roofing shingles, torn flashing around your chimney, overflowing gutters, inadequate roof ventilation, ice dams or snow accumulation during winter months, or excess humidity and rising heat in your attic, there are a number of ways that moisture can slowly make its way into your roofing system and cause rotted roof decking.

Cost Of Roof Inspection

Having a roof inspection done helps to identify potential issues, provides solutions on what needs fixing, determines the condition and lifespan of your roof, and can help you keep your roof in good condition. As previously mentioned, its recommended that you have an inspection done twice a year, or after a major storm, to help you get ahead of problems before they become large or expensive.

Not to mention, a roof inspection will help determine whether your roof sheathing is damaged, rotted, and needs to be replaced. The average cost for a roof inspection is between $100 and $600, with most homeowners paying around $350 for both an internal and external inspection on a 1,500 square foot sloped roof. The actual price that you pay for a roof inspection varies based on the size, material, pitch, and condition of your roof.

Related Guide

Replacing Roofing Shingles Should We Add Plywood On Top Of The Original Pine Decking

Hey GBA, Were planning to replace our roofing shingles on a 1 story ranch built in 1950s located in Massachusetts. Inside the attic we see the roof decking is 3/4 or 7/8 x 12 pine boards. The boards appear in good condition but I was curious if we should add a layer of 1/4 or 3/8 plywood on top of the pine decking prior to installing new shingles. I thought the reason for doing so would add these benefits. 1. Seal the number of gaps between the pine boards. Ranging from 1/16 to 1/4. 2. Provide a more stable sub surface for the shingle material. 3. Adding a thin layer of plywood would offer better moisture resistance/durability compared to adding a layer of OSB.

Attached is a photograph of the new baffles next to the pine decking.

Read Also: How To Put Down Metal Roofing

Four: Install The First Metal Roof Panel

Once youre ready to start installing the metal panels, youll work from left to right. Start at the bottom of the roof. Use the chalk box to snap a vertical line ¼ from the roofs rake edge and square with the eave.

The rake edge is the part of the roof that sits above the house. It helps water flow off the roof and onto the ground without running down the side of your home.

Place the first panel into position on the bottom, left side of the roof. Overlap the roofs edge by one inch and work up toward the ridge. Use the 1 ½ galvanized metal screws to secure the panel to the decking. Place a screw about every 12 to 16 inches apart.

Lazy / Irresponsible Builder / Roofer

Harold

Additionally, the rafter spacing was not a standard 16 on center and not even the odd 24 OC rafters were not evenly spaced at all. Some had 17 of spacing some were 19, 20, 21 etc.

Whoever built that house, really did not care much for the quality, or the additional work required in properly laying down the plywood roof sheathing.

This video demonstrates exactly what we discovered:

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Is Plywood Good For Roofing

Plywood is good for roof decking owing to its structuralstability and pocket-friendliness, so you have nothing to worry about if youre on a low budget.

It dries quickly upon exposure to moisture , protecting the roofing from damage.

Plywood is a product of joining several layers of wood together hence theres enough strength in the plywood.

As a result, plywood can support the heavy weight of the roof. Besides their outrageous strength, they are lightweight.

When wet, plywood swells exceeding its normal size and return to its original size after drying. But after continuous exposure to rain, the damage might set in.

Hence, use an epoxysealer or latex-based paints to waterproof the wood and ensure its longevity.

Can You Overlay A Shingle Roof

Overlay: With an overlay, you keep your current shingle roof, and then shingle on top of it instead. It is important to know that this option can only be used if your roof has not been previously overlaid.

How do you replace rotted plywood on a roof?

How to Replace Rotted Roof Decking

  • Step One: Estimate the extent of the damage.
  • Step Two: Remove the roofing.
  • Step Three: Measure the area.
  • Step Four: Cut out rotted wood.
  • Step Five: Cut the replacement decking to fit.
  • Step Six: Position the replacement.
  • Step Seven: Secure the decking.
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    New Sheathing Over Old Ashpalt Shingles

    We have an Economy Dwelling, that has 3/8 plywood for the roof sheathing. And when the new shingle roof was installed about ten years ago, they didnt pull the backer off the sticky on the tabs. The building is in a high wind area, and all of the tabls are breaking off.

    I requested quotes to strip off the existing shingles and felt, and then install 5/8 sheathing, ice & water, new felt, and new asphalt shingles.

    One of the guys who gave me a cost proposal for the new roof proposed to install the new sheathing over the top of the existing roof, and save teh cost of the tear off.

    Is this a good idea? There wont be money in the budget to touch this roof again for twenty years.

    I know I could do it, and it would probably last the ten years left untill I retire, but I dont like to work that way.

  • …_leave_on_or_take_off__-_steep_-43-821-v2.pdf

    Adding another layer of plywood OVER shingles and plywood and then adding additional shingles sounds like a fly by night solution and could well exceed the design loads for your roof framing.

  • |#2

    Right — the tabs aren’t supposed to be pulled off Tabs breaking off probably is due to cheap shingles, but could be exacerbated by the lousy sheathing.

    3/8 is definitely too flimsy for roof sheathing, though. Pay the money to do it right and rip off the old shingles.

  • Should Roof Decking Be Repaired Or Replaced

    TIPS FOR RE-DECKING A ROOF ON AN OLD HOUSE

    If youre wondering if you can fix the issues with your roof decking by performing a quick patch job, think again. When it comes to rot, repairing your roof decking is simply not an option it must be completely replaced. In fact, the longer you wait without replacing your damaged roof decking, the more problems that can arise, leading to more mold and mildew growth and expensive repairs.

    Read Also: How Often Should You Clean Your Roof

    Finding The Right Roof Sheathing Material

    As was the case on this roof, dry rotted 3/8 plywood would not hold the nails even if they were long enough you could pull them out by hand that is how weak it was. This means that you MUST replace old roofing plywood. Here is approximately how much different options cost:

    5/8 inch $26.87 per sheet. This is the BEST product to use, because its very sturdy and high quality. If there is water damage it will preform significantly better than the 1/2 plywood. Note, that when you buy in bulk, the price drops to $24.18 per sheet. Bulk pricing is for at least 58 sheets or 18.5 squares. If your roof is smaller than this, you can still request the pro to buy 58 sheets, and use what is left over for other home improvement projects.

    1/2 inch 24.85 per sheet. This is what most people use, and its ok quality. However, think about it this way: the difference in price between this and 5/8 is $2 per sheet or $6 per roof square. If the total job is 20 squares, the total material price difference is only $120 dollars, and you will be getting a significantly better quality material. Bulk pricing for 1/2 inch is $22.37 per sheet, and you need to buy 70 sheets.

    OSB roof sheathing about 60% cheaper than standard plywood.. While its allowed by code, we strongly advise against using OSB for sheathing. The minute any moisture gets in, its starts to break apart within 2-3 months. Then, you will need to do expensive repairs, and will actually waste hundreds of dollars in the end.

    Plank Roof Decking: Is It Time To Replace Yours

    Often, when we go out to someones home to give them an estimate to replace their roof, we inspect the roof decking. We check for rotten wood, signs of leaks, dry rot, ventilation, and the type of roof decking. The type of roof decking is an often overlooked component of the roofing system. It is the foundation on which the roof is built. Without a proper foundation, the money invested in replacing the roof can be wasted. In this article, we will be taking a closer look at plank roof decking.

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    Dry / Rotted Plywood Does Not Hold Nails Well

    As was the case on this roof, dry rotted 3/8 plywood would not hold the nails even if they were long enough you could pull them out by hand that is how weak it was. This means that you MUST replace old roofing plywood. Here is approximately how much different options cost:

    5/8 inch $26.87 per sheet. This is the BEST product to use, because its very sturdy and high quality. If there is water damage it will preform significantly better than the 1/2 plywood. Note, that when you buy in bulk, the price drops to $24.18 per sheet. Bulk pricing is for at least 58 sheets or 18.5 squares. If your roof is smaller than this, you can still request the pro to buy 58 sheets, and use what is left over for other home improvement projects.

    1/2 inch 24.85 per sheet. This is what most people use, and its ok quality. However, think about it this way: the difference in price between this and 5/8 is $2 per sheet or $6 per roof square. If the total job is 20 squares, the total material price difference is only $120 dollars, and you will be getting a significantly better quality material. Bulk pricing for 1/2 inch is $22.37 per sheet, and you need to buy 70 sheets.

    OSB roof sheathing about 60% cheaper than standard plywood.. While its allowed by code, we strongly advise against using OSB for sheathing. The minute any moisture gets in, its starts to break apart within 2-3 months. Then, you will need to do expensive repairs, and will actually waste hundreds of dollars in the end.

    What Happens In The End

    Adding New Siding Over Old T1

    All of the issues described above often result in new roofs lasting less than 3 years.

    So there you go trying to save $1200-2000 on roof replacement by not removing old shingles and not repairing / replacing rotted plywood, will usually cost at least $4000-6000 more just in few short years. And this does not include any interior damages.

    Think about it before you spend your money.

    Oh and also if the roofer offers or insists on doing the second layer my advice to you kick them out immediately.

    Average Roof Replacement Cost in US:

    Low End

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    What Makes A Roof Need To Be Replaced

    What makes a roof need to be replaced? When youre facing a problem with your roof, especially a problem that might mean you need a whole new roof, you might decide its time to learn a bit more about this home feature and what caused it to fail. You may be especially concerned if youve been told that not only do you have to replace your roofs shingles, but also the roof plywood underneath them! How did your roof get so seriously damaged?

    Roofs are often taken for granted, especially in California where the lack of rain makes us a bit more complacent about leak protection. Most homeowners dont know how to maintain, repair, or even examine their roof. If you dont know what can cause roof damage, you dont know how to protect your roof from it.

    Well, not to worry. This guide will explain what makes a roof need to be replaced, what causes roof leaks and rotten plywood, what you need to consider for roof replacement and much more. In this article, weve sought to answer your most common questions about roof replacement and repair.

    What Causes A Roof Leak

    Homeowners often ask what causes a roof leak. You may be asking because you have a leak and dont know what caused it, or you may wonder whether your roofs problem will eventually, cause a leak, or if you can afford to leave it. Well do our best to answer your most common concerns about what may cause a roof leak, but you should ultimately ask a professional to inspect your roof if you have concerns.

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    Plywood Over Shiplap Roof

    You can use plywood over shiplap to protect your roof, as shiplap has been in existence for a long time. So, houses with shiplap for roofs have become aged and brittle and dried, therefore, starting to leak.

    Thus, protecting the home becomes a priority, hence, the need for plywood over the shiplap roof.

    So, you can put plywood over a shiplap roof. You can certainly do that, and here is why. Read more to know if you can put Plywood Over Tongue & Groove?

    But, before we get into that, let us discuss exterior grade plywood first, as this forms the basis of our discussion on whether you can cover your shiplap roof with plywood or not.

    Using plywood over a shiplap roof can protect your roof as the resin in the shiplap dissipates and becomes brittle, causing the roof to leak. However, removing the entire shiplap takes time and money. So, replacing plywood over a shiplap roof with exterior grade plywood is the best way to save time and money.

    • Tongue-and-groove boards

    Is It Common For A New Roof To Leak

    How to install a new roof deck over 3/8″ plywood

    No, a new roof shouldnt leak. A leak in a new home, or in a new roof, almost certainly means that your installer made a mistake or one of your roofing products had a defect from the manufacturer. A reputable roofer will be happy to return and correct their mistake or help you make a claim with the manufacturer.

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    Plywood Over Plank Roof

    The roof is one of the most crucial structures in buildings since it serves as protection.

    It shields the interiors from harsh weather conditions and environmental discomfort. Most importantly, everyone wants roofs that will keep functioning for years.

    However, for a long-lasting roof, you need quality materials for the construction.

    Among these elements is the plywood, a layer beneath the roof. But why should I use plywood for roof decking?

    Plywoods are ideal for roof decking because its strong, durable, cheap, and lightweight. Their ability to readily absorb and release moisture swiftly puts them at an advantage over other roof sheathing materials. Besides, plywoods are easy to work on and will support the roofing weight.

    What Thickness Plywood Do You Use 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.

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    Can You Put New Plywood Decking Over The Existing Plywood

    plyply

    I have installed new plywood over existing numerous times with out problems.The new plywood will be thinner than code because when combined with the existing you will still be exceeding sheathing requirements/codes.Make sure your roofer staggers the new plywood joints so it off sets the existing.

    Do you roofers think this should be a tear off and redecked if the existing is in good shape, even though this will be the 4th shingling?And if it is covered with thinner decking on top of the existing, aren’t you defeating the purpose of a new deck not to mention the extra weight? I mean will there be enough meat in the decking for the fasteners?I guess that depends on the thickness of the new decking on top of the old?Is it customary to replace decking on the 4th roofing?

    replace the bad

    Why Is My Roof Decking Damaged

    Why does siding buckle? :: Village Roofing &  Construction

    Leaks and condensation are the two most common causes of a rotting wood deck. It makes sense to look for deck rot around notorious leak points, such as skylights, roof penetrations and anchor points for roof-mounted items. In order to fix the problem, you first need a professional roofer to resolve the underlying leak.

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