Battens Over Solid Sheathing Improve Wood Roof Venting. Open sheathing may also be chosen for economic reasons, but only if used with roofing systems such as metal or tile, which have the structural capacity to span between sheathing boards. Shingles are then attached to the square planks of wood. A panel marked 32/16 may be used for roof sheathing over supports spaced up to 32 inches o.c. You could always opt for thicker roof deck panels, but for a shed there is no need to go thicker if your framing is of standard width. For example, the roof may be braced with diagonal metal straps applied to the top of the sheathing or with a layer of plywood or OSB over the decking. recommended for roof sheathing attachment in high-wind areas. Metal, tile, and shingle roofing may also be applied to solid sheathing. That means the edges have been waterproofed, which makes it much less likely water will penetrate the board. This got me thinking about how thick my roof sheathing thickness should be on the shed I built. The sheathing is usually 1×4. Finally, code requirements do not differentiate between types of roof decks. Solid board sheathing may also be used at these exposed locations. Plywood is more expensive but slightly stronger. For plywood, which is slightly stronger than strand board, ½” thick is appropriate. There are even different types of plywood of the same thickness that will be rated for different spans, so it is critical to pay attention to the labels on the actual panel. Sheathing is installed once the roof structure is built. It spans the rafters to support the roofing and, in the case of panel sheathing such as plywood or OSB, it acts as a diaphragm with the walls to resist horizontal loads. If you get ⅜” panels that say 24/0, it can span up to 24” between framing members. It takes water longer to penetrate it, but once it gets into the sheet then it takes a much longer time to dry. Standard roof sheathing thickness is ½” to ⅝” thick. Never attach roof sheathing with staples; 8d ring-shank nails should be used instead. This can be done with a straight piece of lumber (6 … Plywood particle board or wafer-board roof sheathing is most commonly used, being low in cost and easy to apply. What is the Minimum Thickness of Roof Sheathing? There are many different types of roof sheathing, the main ones are: Today the most common types of sheathing are plywood or strand board. Many builders who are redoing a roof that has original dimensional lumber as a roof deck will put plywood or OSB over the top before finishing the roof with new roofing material as it is simply a more reliable substrate than many pieces of lumber on end. The number beneath the grade is the span rating. Truss Spacing and Design for Sheathed Post Frame Roofs In most instances, there is not a structural or Code requirement for solid roof sheathing (plywood or OSB – Oriented Strand Board) to be placed below through screwed roof steel for post frame buildings. Another factor is how far apart your trusses or rafters are spaced. The roofing material is heavy, so 1×6 or 1×8 or 2×4 open sheathing is practical. For areas with extreme snow, look for panels that have total loads of 50 psf – pounds per square foot. This type of roof sheathing is used under wood shingles and shakes, which usually require ventilation on both sides of the roofing material. Values in the table are based on APA-rated panels continuous over two or more spans with the long dimension of the panel perpendicular to supports. Bracing may sometimes be omitted on hip roofs because the shape of the roof provides the bracing. In some regions, the common practice is to place a moisture barrier over open sheathing to keep out wind-driven rain. The roof's sheathing helps to keep the roof trusses or rafters properly spaced, and is the strength that holds the entire roof together. ROOF SHEATHING FASTENING SCHEDULEa,b,c,d,e 8d Common (0.131 x 2-1/2 inches) or Ring-Shank (0.135 x 2-1/2 inches) (Except Where Noted) for Exposure B, Enclosed Buildings, Roof Framing Spaced 24 inches o.c. A thicker panel may be required for 24” compared to 16”, so if you have larger gaps between the framing, consider a thicker substrate. sheathing thickness is 15/32 inches and less, roof sheathing is required to be fastened with ASTM F1667 RSRS-01 (2 3 / 8" × 0.113") nails. When you purchase roof decking, it will have an “APA” stamp with two numbers beneath, divided by a slash. Probably, but the key is not to sheath using the minimum thickness. However, it is considered good practice to leave a 1/8" gap between sheets, and that is … roconnor (Robert J. OConnor) July 8, 2006, 5:20pm #3 There are no IRC requirements for spacing wood sheathing that I am aware of. The structural panels act as a diaphragm to transfer lateral loads at the plane of the roof to the walls. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. Here there are two basic options. It is most often OSB – a type of particle board – or plywood. ZIP System roof assembly combines our revolutionary integrated sheathing and flashing tape or liquid flashing to provide a sealed roof for protection against moisture intrusion during construction or if high winds strip the roof covering away. Each of these factors plays a role in determining how many nails you'll need to use per board during roof sheathing application. If you are considering battens in place of a solid substrate, just know that strand board or ply acts as a noise barrier as well as a secondary moisture and temperature barrier. The materials used for sheathing are typically oriented strand board (OSB), plywood, or composite. The table is for comparison and approximating purposes only. Fastener Spacing It is extremely important to have proper fastener spacing on all panels. or Less Roof Fastening Zone Wind Main Sheathing-to-Gable- Overhang Velocity Roof End-Wall Framingg (eaves) (3-Second Panel 123 2 3 2 3 Roof-sheathing material must be coordinated with the roofing itself, since each type of roofing has special requirements. Always check for level nailing surface. The thickness of your roof sheathing is important. For sheathing spans greater than 24 in., tongue-and-groove edges, lumber blocking, or panel edge clips are required at edges between supports. Thickness will range from 3/8 to 3/4 inch depending upon local code. live load and 10-lb. He is passionately interested in home improvement, renovation and woodworking. The following are common panel thicknesses recommended… The typical thickness range for sheathing is 3/8 to 3/4 inch. The everyday sheathing used on the body of a roof is not rated for weather exposure, so when exposed eaves and/or rakes occur at the perimeter, a different (more expensive) weather-rated grade of plywood or OSB must be used. live load for Douglas-fir or southern pine species. Metal and tile roofing may be applied to either solid or open sheathing. If that is the case, you’ll find that your framing can support thinner panels than if an edge does not sit directly above a framing member. A board that stays wet longer is prone to sagging, which is why strand board tends to sag over time on many homes. One thing I noticed was that the entire house frame was covered in OSB – even the roof deck. Roof sheathing, or roof decking, is a layer of wood boards attached to the roof’s joints and trusses. A complete resource that includes the best materials and the right techniques to build a sturdy, leak-free, attractive roof on any house. Finally, if you are going to sheath a shed that isn’t heated, then OSB would definitely be a better option, provided you install the roofing material properly. Why? Because the APA – the Engineered Wood Association – creates labels for every piece of lumber they certify, OSB or plywood. If you are using OSB for your roof deck, then ⅝” is the recommended thickness. To figure out for the sheathing snap line, swing the square over to the pitch of the roof, in this case, it is a six-pitch, and strike a line right there. The span rating on FLOOR SPAN panels appears as a single spacing in inches for roof sheathing. Therefore, there are many options available. Thus not all sheathing was created equal. When it comes to choosing a thickness for the solid decking to put atop your framing on your shed or home, one of the primary considerations should be the weather. You lose all of that if you opt for battens. Sheathing at exposed overhangs must be exterior or exposure 1–rated and must be thick enough to hold a nail or other roof fastener without penetration of the exposed underside. Wood shingles or shakes require spacing equal to the exposure of the shingles or shakes—usually about 5 in. It also serves as a secondary barrier between your house and the roofing material in keeping water out and heat in, to some extent. Insulation requirements will vary with climate and with roofing material. dead load, the minimum rated by the APA—The Engineered Wood Association. Become a member and get unlimited site access, including the NOTES: Panel spacing is an APA RECOMMENDATION, to provide installers with a means of minimizing the potential for panel buckling; however, it is not a requirement. to 14-in. Design depends on type of metal roof: exposed or hidden fasteners; board and batten (pan and ridge) panels; shake and shingle panels; panel or tile system; standing seam; etc. However, if you are retrofitting an old house or shed, you may encounter unusual spacings which will indicate your roof decking may need to be thicker than the spacing and label indicate. Thicker panels will result in a more solid roof deck and resist bowing between the rafters or trusses. A strong, resilient roof is a home’s first line of defense when the roof deck is exposed to weather. The simplest approach is to eliminate overhangs (see A in the illustration), in which case the roof plane effectively terminates at the edge of the building, the details are simplified, and the thickness of the assembly is not perceived. in wet weather conditions. Sagging roofs are very common – and visible – and are easily rectified at the time of install. in the field for supports at 48 in. In this article, we’ll go over some tips for choosing the right sheathing thickness for your shed or house, including the types of substrate, techniques for installation, and what works best in different geographic areas. Either the main rafters of the building are extended, or structure extends from the insulative layer. Install ⅜ inch in from the edges and follow the building code or panel manufacturer’s spacing instructions. Snow load should factor into your decision in terms of how thick your strand board or plywood will be beneath your exterior shingles or metal roof. Many metal roofing dealers specify minimum of 7/16" sheathing. Description - These are framing videos of an Oakland County Homes Near Birmingham which was designed and built by Hunter Roberts Homes. support spacing when the panel is used for subflooring. The second number is the maximum o.c. Will thicker sheathing help mitigate that problem? The thickness of the insulation above the sheathing can also be an aesthetic challenge, especially at the eave. Verify span with panel rating. 30 felt underlayment, install vertical 2x battens lined up with the rafters beneath for solid nailing. An 8d nail is 2.5” long and is more than enough to adequately fasten most thicknesses of roof substrate. For a more solid roof, reduce spans or increase thickness. The label clearly states maximum spans and loads allowed for that piece of roof substrate. Recommended Thickness of Shed Roof Sheathing, minimum requirement for roof sheathing is ⅜” thick, OSB (oriented strand board) – uses adhesives compressed with layers of wood chips that alternate direction between each layer, Plywood – compresses large, ultra-thin sheets of wood into a sandwich using adhesives and heat to form one board, Dimensional Lumber – an older way to sheath a house, in which tongue and groove lumber was frequently used or 1” lumber butting up against one another. Roofing Project Guide. A thicker panel means less sagging and a stronger roof deck. Wood structural panel sheathing shall be fastened to roof framing with RSRS-01 (2 3 / 8 " × 0.113") nails at 6 inches (152 mm) on center at edges and 6 inches (152 mm) on center at intermediate framing, unless roof diaphragm design requires a closer spacing. The APA table has a span rating for the sheathing installed with, or without, H-clips, and the span rating is the same both ways. For economic and structural (lateral-load) reasons, solid sheathing is almost always plywood, OSB, or other structural panels. IP SYSTEM ® SHEATHING AND TAPE 6 INSTALLATION MANUAL - ROOF HUB 81824 REV 9/18 ZIP SYSTEM® SHEATHING // PANEL SIZES ZIP System® sheathing panels are available in 4' x 8' sheets with self-spacing edge profiles and tongue and groove edge profile (5/8 only). And if you are looking for a deal, it may pay to hesitate before you go cheap and purchase ⅜” panels. Strand board that is tongue and groove makes for a very straightforward install on your shed. To stabilize the rafters, support the roofing material, and hold the entire roof together, roof sheathing is installed. There is no upper limit on how thick your roof substrate is. Roof sheathing is structural material that spans across the roof trusses or rafters, provides a diaghram for shear strength of the structure, resists seismic and wind loads, encloses the building, and provides a base for the roofing materials. Make sure they are 1.5” long, which would work for ½” thick panels. Sheathing with a thickness of less than that is much more likely to result in bowing between framing which could potentially compromise your exterior roof material. The issues are most complicated at the eave where the top of the wall is separated from the insulative layers by the thickness of the rafters. Care must be taken to protect panel edges from the weather by the use of trim or edge flashing. range. Check with local codes and with roofers for accepted local practices. Of course, a rake design must be coordinated with whatever eave design is chosen. Spans are based on a 30-lb. Since there are so many layers in OSB it is somewhat heavier than plywood. When you replace a roof on a home that was built before the implementation of the statewide Florida Building Code on March 1, 2002, the nailing of the roof sheathing (decking) must be brought up to current standards for hurricane resistance as part of the installation of the new roof. This type of sheathing is necessary for composition roofing and built-up roofing, which have no structural capacity themselves. Thickness allowed depends on how far apart rafters or trusses are spaced and the rating of your roof decking. If your deck is thicker, then you’d want #12 wood screws at 2” long. Shingle and shake roofs may also be applied to solid sheathing at exposed eaves and rakes and similar locations. spacing in inches for roof sheathing. When sheathing a roof, plywood or OSB can be utilized. Sheathing recommendations in relation to roofing types are as follows: Composition and built-up roofing must be applied to solid sheathing because these roofing materials do not have the structural capacity to span between the boards of open sheathing. Once you start buying panels that are greater than ⅝” thick, you’ll notice the cost rise significantly. After laying down No. The actual span capacity depends on roof pitch, species, live-load values, and end-joint pattern. Plywood dries much faster than OSB because it is not as dense. Thus, for sheathing a roof with metal panels, you’ll want to stick to ⅝” panels. Roof sheathing is the solid surface below your exterior material, whether it’s shingles, metal, or another type of covering. o.c. More protective of the walls and almost as simple is to add a porch roof at a lower slope (see B). The strand board, besides being cheaper, also works extremely well with tar paper. o.c.). range. The recommended thickness for roof decking on a shed is ⅝”. ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHING. Save money by using a strand board, then use that savings to up the thickness a little bit. While that might not sound like much weight, just know that you’ll multiply that number over the number of square feet on your roof. For the most common roof sheathing in our area, which is 1/2” nominal (7/16” actual) sheathing over trusses or rafters at 24” on center, there is no requirement for H-clips. That minimum number refers to either OSB or plywood. A panel marked 32/16 may be used for roof sheathing over supports spaced up to 32 inches o.c. 24” and 16” are the most common spacing, and you’ll often find 16” standard for rafters and 24” standard for trusses. The table assumes a 30-lb. Batts are often chosen for colder climates when the thickness of either type of insulation (rigid or batts) requires adding a second level of structure above the decking to support the roof. or for floor sheathing over supports spaced up to 16 inches o.c. Sheathing is not meant to be a moisture barrier or vapor barrier primarily. The RSRS designation Spacer-type panel edge clips may also be used for roof sheathing applications. What Size of Roofing Nails for Roof Sheathing? In that case, strand board is best instead of plywood. Therefore if you pick up some ⅜” sheathing that is 12/0, that means the max gap it can bridge between rafters or trusses is 12”. The rough surface of OSB as compared to the smoother surface of plywood allows the tar paper to hold better and makes installation much faster. In the past, roof substrate was simply dimensional lumber but today’s options are cheaper and easier to install. Minimum sheathing requirements dictate that ⅜” thick is the lowest you can go in terms of thickness. Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof. The minimum requirement for roof sheathing is ⅜” thick. The two basic types of sheathing are solid sheathing and open sheathing. 2. The system provides a structural diaphragm and is appropriate for all but wood shingle or shake roofing, which requires ventilation. o.c. T&G sheathing (decking) is most often used for exposed ceiling applications. It is important to note that there is no “standard” sheathing thickness, at least officially. Preformed metal roofing is lightweight and runs continuously in the direction of the rafters. With a porch roof, the thickness of the assembly stops at the exterior wall, and a simpler, uninsulated, self-supporting porch structure (that can be sheathed with the same T&G sheathing as the interior ceiling) extends beyond. That is more than enough strength to keep the snow from falling into your structure. The placement of insulation above the structure of the roof that is necessitated by exposed sheathing creates a thickness of the assembly that must be addressed with unique detailing at the edges of the roof (eaves and rakes). Start your subscription today and save up to 52%. These ratings are minimum. The roofing material is heavy, so 1×6 or 1×8 or 2×4 open sheathing is practical. This can be done with a straight piece of lumber … Of course, nearly all frames are designed to fit roof sheathing edges, so when you install your panels you’ll be able to screw or nail your panel edges into the framing. Check local codes and with design professionals for higher loading, such as greater snow loads, or heavier dead loads, such as concrete tiles or other heavy roofing. Always Check for a Level Nailing Surface. I'd rather use 1/2 … SPAN (inches) … What is the Standard Roof Sheathing Thickness? The sheathing is usually 1×4. Therefore you’ll want to ensure you have the most solid substrate possible for that metal roof to screw into. Some manufacturers may require a space at the … Concrete tiles, depending on the type, may be installed on open sheathing spaced in the 12-in. for shakes. to 14-in. Rigid insulation is usually the most practical because of its thin profile, but it is more expensive than batt insulation. If you opt to use screws, then #10 wood screws would work. Roof decking that will have metal for its outer roof covering is no different than sheathing a roof that will have asphalt shingles. Then we're going to use a scrap of 2x4 to space off the square and strike a line there. Rafters are spaced at wide centers since the decking will span more than 24 in. Concrete tiles, depending on the type, may be installed on open sheathing spaced in the 12-in. The ability of the sheathing to span between supports depends on the spacing of both rafters and sheathing and on the type of roofing applied over it. Is there any reason that I would want to use 3/4" sheathing? OSB board is preferable to plywood for sheathing a shed. Drawings should be checked to verify the required spacing; closer spacing may be required at corners, edges, and ridges. Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine. What’s Better for Roofing: OSB or Plywood? Spacing of open sheathing depends on the type of roofing it will support. From the APA Guidelines: “The left-hand number is the maximum recommended center-to-center spacing for supports in inches when the panel is used for roof sheathing with the panel’s long dimensions across supports. o.c. When it comes to sheathing your roof, however, it never hurts to go thicker. Another consideration is if your rafter or truss spacing allows you to place your sheathing – usually 4’x8’ panels – so that each edge of the panel is supported. Handling large panels on a windy day while on a roof sometimes doesn’t end well. At exposed roof overhangs, the sheathing must be rated for exposure to the weather. Therefore if you have a total of 2000 square feet, then the total load spread out over your roof is multiplied times 50, which is 100,000 pounds. Expert insights on techniques and principles. Choose an exterior C/D grade. Wood shingle and shake roofing is best applied over open sheathing because the spacing between the open sheathing allows the roofing to breathe from both sides, prolonging its life. Both roofing materials have the strength to span across open sheathing, but there is no advantage for either in having them breathe from both sides. This makes it simpler for the consumer to pick out the right piece of product under their finished roof without having to worry about telling the difference between types of wood products. The rating appears as two numbers. Even you have a ⅜” thick piece of strand board and the same for plywood, they may likely be rated for different spans. There are usually only several layers of plywood per sheet while there are up to 50 layers of wood chips in a sheet of strand board, plus much more adhesive than a sheet of ply. Most complicated is to extend an eave at the same pitch as the main roof (see C). Dimensional lumber is not used because it would be much more expensive and provides a lesser surface for nails or screws due to gaps between all the boards. In very windy areas, solid sheathing is often used. Even in your neighborhood you’ll notice homes with roofing that sags. For instance, there are ⅜” panels rated for 24” rafter spacing. A structure's roof truss spacing can vary from every 12 to 24 inches. In most cases, 1×6 sheathing at 24 in. OSB is the better option for roof decking because it is cheaper and comes in a wider variety of larger sizes than plywood. Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers. The adhesives that bond the strand board are also waterproof. Projecting the eave from the insulative layer has the advantages of both raising its height and having more control over the thickness. There’s a new house being built on my street and they’ve just finished up the framing and sheathing. Roof Sheathing Basics The skeleton of a roof is formed with rafters or trusses, generally spaced 16 inches or 24 inches apart from the center of one rafter to the center of the next. Combinations, of course, are also possible and often appropriate. Omit roof sheathing panels in each course of sheathing between sections and install “fill in” panels later to complete roof deck installation prior to applying roofing. is adequate. Remember that ⅜ is very thin, and any load placed atop ⅜” panels will likely, over time, make the strand board or ply panels sag even if placed at the rafter/truss spans as designated by the panel label. Use two clips for spans of 48 in. I wish you luck on your roof project. Insulation for an exposed ceiling must be located above the sheathing. Roof sheathing comes in grid-marked 4-by-8-foot sheets, and should be installed perpendicular to the frame. Strand board does not react as well to moisture as plywood does, but it will have a more consistent thickness and fewer weak spots – like knots – than plywood. The first number is the maximum span for roof sheathing, assuming that the panels are installed with the long dimension across three or more supports, with the edges supported. Because this sheathing material does not provide a diaphragm at the plane of the roof, other means of bracing the roof against horizontal loads must usually be employed. support spacing when the panel is used for subflooring. • LP OSB sheathing roof panels have a course-textured top surface ... a minimum 1/8” spacing between panel ends and edges. Standard recommended fastening is 6 in. Open, or skip, sheathing is usually made with 1×4 or 1×6 boards nailed horizontally to the rafters with a space between the boards. Open sheathing, also called skip sheathing, is composed of boards spaced apart. Overall metal roofs use less nails than asphalt shingle roofs, so you have fewer fasteners holding everything together. RSRS-01 is ring shank roof sheathing nail meeting the specifications in ASTM F1667. Remember to always use your fall protection when working on the roof. • OSBWall Installation sheathing panels are available directly from LP’s manufactur-ing plants by railcar, as well as piggyback and truckload shipment. Panel Selection, Handling and Storage Table 2. in the field (6 in. Roof Sheathing. For example, solid sheathing at exposed overhangs may be combined with open sheathing on the rest of the roof. Consult with local codes and builders for the accepted practice. This gap needs to be insulated and spanned with a continuous air barrier. The standard panel size is 4 ft. by 8 ft., so rafter or truss spacing that falls on these modules is most practical. Correct spacing between panels when framing will absorb most of this expansion, but where insufficient spacing or dense nailing patterns prevent movement, a net expansion of floor and roofing decks may result in unevenness or buckling. The second number is the maximum o.c. And while plywood may dry faster than strand board, it’s important to note that all strand board roof decking you buy these days has blue edges. Alternative methods of providing lateral stability, such as diagonal bracing, must be used with open sheathing. The second number is the maximum span when the panel is used for floor sheathing. Often you can see the outline of the rafters or trusses beneath the shingles. But this is a simpler issue to resolve because the top of a wall supporting T&G sheathing need not be separated from the sheathing as it needs to be at the eave. When an exposed ceiling is desired, solid sheathing may also be constructed of solid-wood tongue-and-groove boards. Spacing Hint: Use a 10d box nail to gauge 1/8-inch spacing between panels. Preformed metal roofing is lightweight and runs continuously in the direction of the rafters. Boards require a minimum of two nails per truss, while sheathing requires six nails due to face width and nail spacing. I'm building a the roof (hip) for a small addition (8x11) and am finally ready to sheath. Lets pretend the roof design details are conventional and so the roof deck sheathing will be 5/8" to 3/4". The requirement became effective on October 1, 2007. Of course, some shed owners, or homeowners, may opt to use battens in conjunction with their metal roof, but battens don’t offer nearly the amount of protection that strand board or ply does. Since this sheathing material does not provide a diaphragm at the plane of the roof, other means of bracing the roof against horizontal loads must be employed. The first number tells you the maximum distance that the panel can bridge between gaps. This … The rafter spacing is 14"OC and unless there's a good reason to use 3/4. at edges and 12 in. in most cases (see the table). Sheathing should be a minimum of 19/32-inch thick. ... Another factor is how far apart your trusses or rafters are spaced. It can also be used selectively at exposed eaves or overhanging rakes. As mentioned above, all types of roof sheathing comes with a label that indicates spacing allowed between framing members. Roof sheathing is the solid surface below your exterior material, whether it’s shingles, metal, or another type of covering. Solid sheathing provides a continuous surface at the plane of the roof. You’ll find that the performance of the OSB will be more than adequate for your shed’s needs. You put underlayment on top of the roof deck to act as a moisture barrier, and your primary vapor barrier will bein your attic, not beneath your shingles or other outer layer. This provides the full benefit of spaced sheathing on top of a solid roof deck. Eugene has been a DIY enthusiast for most of his life and especially loves being creative while inspiring creativity in others. There won’t be any condensation issues, so your roof deck is liable to stay dry. One of the difficult parts about figuring out roof coverings for your shed or house are all the options.