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How Much Plywood Do I Need For My Roof

What Type Of Nails For Felt/underlayment

OSB vs. Plywood: Which Should You Choose for Your Roof Deck?

Roofing felt is a type of underlayment that professionals install beneath a roofs shingles. Unlike selfadhering underlayments, such as ice and water protector, felt underlayment needs to be fastened in place with nails. Specifically, youll need roofing cap nails. These have large plastic caps for heads, which help prevent water intrusion.

Dont confuse these cap nails with gasket roofing nails. Roofing nails with gaskets are intended for metal roofs. The gasket is rubber, not plastic. You want roofing nails with plastic washers for roof underlayment.

How Much Does Plywood Cost

A regular piece of plywood sheathing will measure 4×8 feet and can be from ¼-inch to -inch thick.

The thicker your plywood, the more youll have to pay for it and its installation. The price you pay for the project will depend on a variety of factors, such as the labor costs. Generally, a sheet of 4×8 plywood will cost about $10.

Note that a plywood sheet thats 4×8 feet will be large enough for a roof area thats 32 square feet. Since the average roof is approximately 3,000 square feet, you can see how installing decking in your home can be very expensive.

Where To Put Vapour Barriers :

“Materials that act as vapour barriers , including certain types of insulation, must be located within the assembly so that moisture moving from the inside to the outside does not condense and accumulate within the assembly. This means that vapour barriers should be located on the warm side of insulating materials.” – Canada Mortgage and Housing Corporation

Manufacturers spec sheets we’ve read claim perm ratings of between 1 and 2 perms, but that doesn’t inspire a great amount of confidence given that that conclusion was obviously arrived at by using the most favourable of the available numbers. At least some of these panels are said to be perforated to allow for increased moisture permeability, but a close look at the panel in the photo above at least, shows no visible perforations. So if they are there, they are no bigger than a needle point.

It would seem then possible at least, for moisture to migrate through the EPS and condense on the sheathing, certainly if you believe the lower of the OSB perm ratings. Without seeing the long term results of insulated sheathing products or at least some independent research on it, It’s hard to know what will happen.

Recommended Reading: How To Extend A Roof

How Much Does Roof Sheathing Cost

During roofing, roof sheathing is priced cumulatively with the rest of the roofing work. You cannot have one contractor lay down the skeleton and another layout the roofing material.

But before the labor charge agreement, the roofing contractors will know which roof sheathing material to use.

Wood, Concrete, and Steel are priced differently. But different wooden materials could be priced the same as they are made from the same material, have the exact measurements, and even the same thickness.

The difference between the OSB and plywood costs around $50-$60, where OSB could cost $600 and plywood $660. It is the cost of installing 500 square feet of roof.

Get Quotes From Competing Contractors

Does This Plywood Or OSB Need To Be Replaced? Pic Included

We recommend hiring a professional contractor for this task. What we dont recommend is for you to hire the first contractor with a good offer. You need to shop around in order to get the best quotes to choose from. If they know that youre shopping around for the best deal, you can expect to get the best quotes. Be sure to also read our article about getting free roof repair estimates.

We made this process easier. All you need to do is to use the form that you see on this page. Complete the form with the basic details asked and send it. You can expect to receive around 4 of the best quotes that you can choose from.

Try this free service today!

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How To Figure Out How Much Plywood To Use On A Roof

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When you are planning to build a new roof or rebuild an existing roof, you will want to have an idea of how much material youll need to cover that roof. If sheathing the roof with plywood, there are basic formulas for roughly estimating the number of 4 foot by 8 foot sheets of plywood you will need to cover your roof.

  • Measure the length and width in feet of each roof slope with the tape measure. A typical gable roof will have identical slopes on each side of the ridge line. Multiply the length by the width to find the square foot area of one slope. Multiply that figure by 2 to get the total roof area. For instance, if the slope length is 40 feet and its width is 20 feet, 40 multiplied by 20 gives 800 square feet. Since there are two identical slopes, multiply 800 by 2 to get a total roof area of 1,600 square feet.

  • 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. Add 10 percent to allow for waste.

  • Things You Will Need

    Choosing Plywood For The Roof

    Choosing the right type of plywood for the roof is one of the most important construction decisions that you will have to make. It determines how long your roof will last and how well it will protect the contents of your home. Both OSB and plywood for the roof have been approved for use, so it may come down to what you feel most comfortable using. Be sure to weigh the advantages and disadvantages of each option before you decide which way to go for your new home or your updated roof.

    Also Check: Skylight For Metal Roof

    When Sheathing A Roof Is Plywood Or Osb Best:

    In an ideal world you would schedule your roof construction during a dry period if possible. Depending on your roofing design, allow time for membranes to be installed, or at the very least get a tarp on it before it sees any rain. Roofs are probably the better of the applications for OSB if you take steps to keep it fairly dry. Severe wetting may lead to swollen edges – that may be noticeable with asphalt shingles, but less so with other materials.

    Plywood Vs Oriented Strand Board

    Getting OSB/plywood sheets on the roof by yourself!

    Strand Board is gaining popularity as a material used for roofing. OSB is a type of wood made up of strands in varying orientations compressed together with adhesive to form a board. This type of wood is typically a cheaper alternative to plywood, but it meets most standards of its alternative.

    There are a few disadvantages to using this cheaper alternative to plywood. The most notable ones are the inability of OSB to hold nails as effectively as plywood.

    This means that the structure of the roof is compromised ever so slightly. The second disadvantage is the way OSB absorbs moisture.

    While it is true that OSB takes a longer time to absorb moisture than plywood, it also takes that much longer to dry.

    While plywood dries down evenly, OSB tends to absorb moisture more around the edges, making it swell and dry down with a ring around the edges.

    Florida Dade County has prohibited the use of OSB for roof decks because of the effects that Hurricane Andrew had on homes that used the material for roofing.

    Also Check: Solar Shingles Cost Per Square Foot

    What Size Plywood For Roofing

    The most common rafter spacing is 24 inches. You can get plywood sheets with a length of up to 4 x 10 feet and OSB comes up to 16 feet long in length.

    Do Most people ask how many sheets of plywood do I need for my roof?

    Most people want to know how much square-fit plywood is needed in the roofing. Obviously, you dont want to buy extra plywood. Which is of no use to you and a waste of money.

    Standard plywood comes in 4×8 feet size. So how many square feet are there in 4×8 feet of plywood? To calculate it, you multiply the length by the width. So 4×8 feet plywood has 32 square feet.

    To calculate how many plywoods are required for your roof. Calculate your roof as if you calculated plywood square feet .

    For example, suppose some area of your roof is 1000 square feet. So divide by 32 into 1000. The number youll get is the number of plywood that you need. In case you need 32 plywood. Always buy one or two extra pieces of plywood for mistakes and wastage.

    Can Metal Roofing Be Installed Directly To Plywood

    Metal roofing should not be installed directly over the top of bareplywood. You do not have to install roofing shingles or other roofing material, but a felt sheet over the plywood is the bare minimum. You may also want to install a slip sheet to protect the felt sheet from potential damage caused by the metal roofing.

    If you install your metal roofing directly on plywood without the protective layers, you greatly increase the odds of the roof leaking. You also run the risk of premature wood rot, as the felt sheet provides a layer of moisture prevention that keeps the wood dry. Even without heavy rain, humidity can build up between the metal roofing and the plywood and ruin the wood.

    The slip sheet is also an important layer. This smooth, industrial paper is laid on top of the felt to protect the felt from the metal roofing material. The metal can heat up from exposure to the sun and adhere to the tar-infused felt sheeting. When the metal expands or contracts with changing temperatures, it can tear or wear away the felt sheeting.

    Read Also: Replacing Roof Trusses

    Most Read Life Stories

    The plywood is nailed to the roof rafters, and unless the builder used a tongue-and-groove plywood or H clips, the long edge can warp in between each rafter. When the workers returned to the attic, they most likely added a 2- by 4-inch block between two or more of the rafters and then tried to secure the warped edge of the plywood using wood screws. What they were trying to do was to force the wood to bend back to normal. Most of the time this type of repair is unsuccessful because the screws used to secure the plywood are too short. Longer screws would come through the surface of the shingles where the roof could then leak.

    To properly repair the cupped plywood, some of the shingles need to be removed to provide direct access to the decking. Unless the roof is leaking, the line you see on the roof is an aesthetic problem, but the cupped plywood is putting an added strain on the shingles either side of the visible line.

    To avoid the possibility of a roof leak, have the shingles removed near the cupped plywood, make the repairs from the roof side and replace the shingles. Have the work done on a warm day when the shingles are pliable. By using care, the shingles that are removed can more than likely be salvaged and reinstalled.

    A Smarter Way To Buy Building Materials

    How Much Plywood Am I Going To Need????

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      Gable Roof Sheathing Calculator

      Estimate the amount of plywood or OSB needed for sheathing a roof.The calculation is based on that the Plywood or OSB sheets are of a 4′ x 8′ size. One sheet = 32 ft²

      This basically calculates the number of sheets needed for a Gable roof.The square footage of a Hip roof area is identical to the square footage of a Gable roof of the same measurements. If you are calculating the number of sheets needed for a Hip roof then for the value of the gable overhang use the eaves overhang dimension, assuming it is the same all around.The amount of waste on a Hip roof will be higher than for sheathing a Gable roof and even more so if you are using OSB sheathing. OSB sheathing has a rough side and a smooth side. You always want to make sure the rough side is up with OSB sheathing. Never install the OSB sheathing with the smooth slippery side up!

      Roof Sheathing Gable Roof

    • building length in feet and inches
    • building width, the “gable side” wall in feet and inches
    • gable overhang in inches
    • eaves over hang in inches
    • The Results

    • roof area in square feet
    • number of sheets needed based on exact square footage of the roof
    • the number of sheets the waste percentage will add
    • Number of sheets needed including the waste
    • Read Also: Skylight On Metal Roof

      How To Calculate Project Cost

      If you know the price per linear foot or board foot, the calculator can work out the total cost of the wood using the formula:

      $$Cost = Price\,Per\,Board\,Foot \times Total\,Board\,Feet$$

      $$Cost = Price\,Per\,Linear\,Foot \times Linear\,Feet$$

      In addition, you can calculate the price per board foot/linear foot for the wood you have purchased using the formula:

      $$Price\,Per\,Board\,Foot = $$

      $$Price\,Per\,Linear\,Foot = $$

      Something not clear?

      See below for two full examples working with different initial criteria.

      Otherwise, make your measurements accurately and enter the values into our online lumber calculator to get started!

      Is Cdx Plywood Good For Roofing

      How to Waterproof a Plywood Roof Deck.

      Moisture Differences

      In reality, CDX plywood can only withstand water for a short period of time. Do not use CDX for roofing, sheds, or other places that are exposed to moisture consistently. The sole exception to this is pressure treated CDX, which can survive for decades without even a protective coating.

      Also Check: How Often Does A Roof Need To Be Replaced

      While Youre At Itcupola

      Tearing off an old roof offers the opportunity to have your roofing contractor add one of these upgrades.

      Before ridge vents became standard, cupolas were used to cool houses and barns. Fitted with louvers, or electronically controlled windows, they help draw cool air in through soffits or open windows, then vent warm air from the top of the building.

      Plywood For Roofing: Everything You Need To Know

      If you want a strong, durable roof, you have to ensure you have installed the correct roof decking.

      This is made up of sheet materials that produce a flat surface so that shingles can be nailed onto it securely, and decking is usually made out of plywood.

      What is plywood, exactly?

      Plywood is a wood-based material thats constructed from thin layers of wood. These are glued crosswise along the grain to prevent shrinkage and swelling from occurring.

      With this in mind, lets explore what plywood is used for in roofing, and why its a good choice. Well also explore what you need to know about the different types of plywood.

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      Plywood Spacing On Roof

      Im putting up a large roof with trusses and wondered about the plywood spacing. I understand it is recommended that I use a little metal spacer between sheets to allow for expansion. Although the spacer is very thin, Im covering a 24 x 52 roof thats a lot of sheets . Thats 6 spacers, both vertically and horizontally. If I assume 1/16th for the spacer, thats a little less than 1/2 space accumulation. Shouldnt I adjust the trusses to accommodate that distance so the spaces stay centered over the trusses centers? Or am I wondering over nothing? Thats 27 trusses on 24 centers. I would appreciate any comments or advice here I really dont need to make a mistake. Thanks

    • |#2

      You should space the trusses to exact dimensions, that is, if it calls for 24″ center to center spacing, you should do just that.

      The little metal things you call spacers may be edge supports. Are they shaped like an H? If so, they are only used on horizontal joints. All the vertical joints must land on a rafter. Their purpose is to clip the plywood on both sides of a horizontal joint together so you don’t have one piece flapping independently from the one above or below. It makes nails go in a bit better and the roof less bouncy when you walk on it, and less chance of nails popping.

    • In Addition To The Types Of Plywood Mentioned Above What Sort Of Plywood Is Utilised For Roofing

      Adding Floor Joists To Attic

      Thicknesses that are considered standard It was 1/2-inch CDX plywood that was the standard choice for sheathing a roof with a 24-inch rafter spacing before lumber companies began selling OSB. The letters CDX denote that it is a construction-grade material intended for exterior applications, and the letters CD indicate that it is 1/2-inch CDX plywood.

      Read Also: How To Add A Gable Overhang

      How Is Plywood Used In Roofing

      Plywood is usually used as a form of roof decking, the material that is placed on top of the roofing structure.

      While we often think of the main roof structure as being what needs to be strong and handle large amounts of weight, the roof decking is a component that has to be strong enough to support the entire system from collapse!

      Since decking is made from layers of wood that are glued together, the grains of the wood run in alternate directions throughout each layer. This gives an even distribution of the woods strength so that its resistant to contracting and expanding. This also prevents it from being weak that it splits when a nail goes through it.

      In case youre wondering, roof decking is one of the most important structures of your roofing system. This is made up of wooden boards that produce the roof frame.

      These boards are basically what your roof shingles and other roofing elements are installed on, so you have to ensure that the decking is strong enough to handle all their weight.

      There are good reasons why plywood is ideal for decking construction. These include the following:

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