Loss of just one panel in a windstorm can lead to total building failure. The second number is the maximum o.c. Shingles are then attached to the square planks of wood. Roof sheathing, or roof decking, is a layer of wood boards attached to the roof’s joints and trusses. Roof-sheathing material must be coordinated with the roofing itself, since each type of roofing has special requirements. 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. The label clearly states maximum spans and loads allowed for that piece of roof substrate. 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. When installing sheathing, use 8d roofing nails. The sheathing is usually 1×4. There’s a new house being built on my street and they’ve just finished up the framing and sheathing. 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. Roof sheathing is the solid surface below your exterior material, whether it’s shingles, metal, or another type of covering. The sheathing is usually 1×4. It can also be used selectively at exposed eaves or overhanging rakes. 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. 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. The first number tells you the maximum distance that the panel can bridge between gaps. The spacing between rafters, as well as the build of the entire structure is inspected. Of course, a rake design must be coordinated with whatever eave design is chosen. As mentioned above, all types of roof sheathing comes with a label that indicates spacing allowed between framing members. This type of roof sheathing is used under wood shingles and shakes, which usually require ventilation on both sides of the roofing material. Standard recommended fastening is 6 in. 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. Beneath those numbers are the maximum allowable live and dead loads that panel can support. support spacing when the panel is used for subflooring. Care must be taken to protect panel edges from the weather by the use of trim or edge flashing. 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. Roof Sheathing. 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. When you purchase roof decking, it will have an “APA” stamp with two numbers beneath, divided by a slash. The recommended thickness for roof decking on a shed is ⅝”. 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. 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. 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). When sheathing a roof, plywood or OSB can be utilized. The structural panels act as a diaphragm to transfer lateral loads at the plane of the roof to the walls. The actual span capacity depends on roof pitch, species, live-load values, and end-joint pattern. More protective of the walls and almost as simple is to add a porch roof at a lower slope (see B). Spans are based on a 30-lb. This type of sheathing is necessary for composition roofing and built-up roofing, which have no structural capacity themselves. Solid board sheathing may also be used at these exposed locations. For economic and structural (lateral-load) reasons, solid sheathing is almost always plywood, OSB, or other structural panels. Concrete tiles, depending on the type, may be installed on open sheathing spaced in the 12-in. Lets pretend the roof design details are conventional and so the roof deck sheathing will be 5/8" to 3/4". Sheathing is not meant to be a moisture barrier or vapor barrier primarily. An 8d nail is 2.5” long and is more than enough to adequately fasten most thicknesses of roof substrate. 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). Always Check for a Level Nailing Surface. Will thicker sheathing help mitigate that problem? What is the Standard Roof Sheathing Thickness? He is passionately interested in home improvement, renovation and woodworking. The thickness of your roof sheathing is important. Either the main rafters of the building are extended, or structure extends from the insulative layer. Roof decking that will have metal for its outer roof covering is no different than sheathing a roof that will have asphalt shingles. 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. The choice of thicknesses actually varies widely depending on what store you shop at and where you are in North America. 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. • LP OSB sheathing roof panels have a course-textured top surface ... a minimum 1/8” spacing between panel ends and edges. I'd rather use 1/2 … 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. Another factor is how far apart your trusses or rafters are spaced. Spacing of open sheathing depends on the type of roofing it will support. Roof sheathing comes in grid-marked 4-by-8-foot sheets, and should be installed perpendicular to the frame. Rigid insulation is usually the most practical because of its thin profile, but it is more expensive than batt insulation. 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. For instance, there are ⅜” panels rated for 24” rafter spacing. 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. 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. The function of sheathing is to provide a smooth, flat, and solid surface for the roofing material to attach to with nails or screws. The requirement became effective on October 1, 2007. The two basic types of sheathing are solid sheathing and open sheathing. The materials used for sheathing are typically oriented strand board (OSB), plywood, or composite. Even you have a ⅜” thick piece of strand board and the same for plywood, they may likely be rated for different spans. 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. There are several approaches that can be employed, each of which will lead to unique detailing specific to the situation. The number beneath the grade is the span rating. You’ll find that the performance of the OSB will be more than adequate for your shed’s needs. Metal and tile roofing may be applied to either solid or open sheathing. When an exposed ceiling is desired, solid sheathing may also be constructed of solid-wood tongue-and-groove boards. Choose an exterior C/D grade. The adhesives that bond the strand board are also waterproof. live load and 10-lb. Insulation requirements will vary with climate and with roofing material. Spacer-type panel edge clips may also be used for roof sheathing applications. In making this choice, the primary factor will be the appearance of the eave—especially its thickness. in most cases (see the table). Open sheathing, also called skip sheathing, is composed of boards spaced apart. The system provides a structural diaphragm and is appropriate for all but wood shingle or shake roofing, which requires ventilation. T&G sheathing (decking) is most often used for exposed ceiling applications. This bracing must be engineered in seismic or high-wind zones or for very large roofs. A thicker panel may be required for 24” compared to 16”, so if you have larger gaps between the framing, consider a thicker substrate. Thicker panels will result in a more solid roof deck and resist bowing between the rafters or trusses. Often you can see the outline of the rafters or trusses beneath the shingles. recommended for roof sheathing attachment in high-wind areas. If you are concerned about moisture getting into your sheathing, then plywood may be a better option. ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATHING. SPAN (inches) … Each of these factors plays a role in determining how many nails you'll need to use per board during roof sheathing application. Check with local codes and with roofers for accepted local practices. 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. You lose all of that if you opt for battens. or for floor sheathing over supports spaced up to 16 inches o.c. I'm building a the roof (hip) for a small addition (8x11) and am finally ready to sheath. o.c. And if you are looking for a deal, it may pay to hesitate before you go cheap and purchase ⅜” panels. Projecting the eave from the insulative layer has the advantages of both raising its height and having more control over the thickness. Metal, tile, and shingle roofing may also be applied to solid sheathing. 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. In very windy areas, solid sheathing is often used. Roof sheathing attaches to the surface of the rafters or trusses to form the structural skin of the roof. 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. Install ⅜ inch in from the edges and follow the building code or panel manufacturer’s spacing instructions. If your deck is thicker, then you’d want #12 wood screws at 2” long. A complete resource that includes the best materials and the right techniques to build a sturdy, leak-free, attractive roof on any house. Combinations, of course, are also possible and often appropriate. If your rafters or shed trusses are widely spaced, or uneven (if it’s an old shed) then the tongue and groove give the edges additional strength, particularly if they aren’t supported by framing at every edge. 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”. 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. in the field for supports at 48 in. Where the sheathing thickness is greater than 15/32 inches, roof sheathing is required to be fastened with ASTM F1667 RSRS-03 (2 ½" × 0.131") nails or ASTM F1667 RSRS-04 (3" × 0.120") nails. This can be done with a straight piece of lumber (6 … Consult with local codes and builders for the accepted practice. 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. Roof sheathing is the solid surface below your exterior material, whether it’s shingles, metal, or another type of covering. The minimum requirement for roof sheathing is ⅜” thick. dead load, the minimum rated by the APA—The Engineered Wood Association. Roof sheathing is one area where it pays to spend a little more money. 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. Preformed metal roofing is lightweight and runs continuously in the direction of the rafters. 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. There are many different types of roof sheathing, the main ones are: Today the most common types of sheathing are plywood or strand board. The table is for comparison and approximating purposes only. 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. 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. The roofing material is heavy, so 1×6 or 1×8 or 2×4 open sheathing is practical. What Size of Roofing Nails for Roof Sheathing? 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 The thickness of the insulation above the sheathing can also be an aesthetic challenge, especially at the eave. That minimum number refers to either OSB or plywood. Panel Selection, Handling and Storage Table 2. Why? Sheathing a shed roof is no different. The roofing material is heavy, so 1×6 or 1×8 or 2×4 open sheathing is practical. is adequate. 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 for an exposed ceiling must be located above the sheathing. Alternative methods of providing lateral stability, such as diagonal bracing, must be used with open sheathing. 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. ... Another factor is how far apart your trusses or rafters are spaced. Wood shingles or shakes require spacing equal to the exposure of the shingles or shakes—usually about 5 in. What is the Minimum Thickness of Roof Sheathing? 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. Fastener Spacing It is extremely important to have proper fastener spacing on all panels. © 2021 The Taunton Press, Inc. All rights reserved. After laying down No. In some regions, the common practice is to place a moisture barrier over open sheathing to keep out wind-driven rain. or for floor sheathing over supports spaced up to 16 inches o.c. It is important to note that there is no “standard” sheathing thickness, at least officially. The following are common panel thicknesses recommended… A board that stays wet longer is prone to sagging, which is why strand board tends to sag over time on many homes. spacing in inches for roof sheathing. Sheathing should be a minimum of 19/32-inch thick. in the field (6 in. It takes water longer to penetrate it, but once it gets into the sheet then it takes a much longer time to dry. It is most often OSB – a type of particle board – or plywood. At that thickness, you can economically sheath your shed while still getting an extremely solid roof substrate that will stand the test of time. Since there are so many layers in OSB it is somewhat heavier than plywood. A panel marked 32/16 may be used for roof sheathing over supports spaced up to 32 inches o.c. OSB is the better option for roof decking because it is cheaper and comes in a wider variety of larger sizes than plywood. Thickness allowed depends on how far apart rafters or trusses are spaced and the rating of your roof decking. For example, solid sheathing at exposed overhangs may be combined with open sheathing on the rest of the roof. Plywood is more expensive but slightly stronger. RSRS-01 is ring shank roof sheathing nail meeting the specifications in ASTM F1667. 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. What’s Better for Roofing: OSB or Plywood? Is there any reason that I would want to use 3/4" sheathing? There won’t be any condensation issues, so your roof deck is liable to stay dry. 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. These ratings are minimum. Finally, code requirements do not differentiate between types of roof decks. I wish you luck on your roof project. o.c.). The table assumes a 30-lb. Because the APA – the Engineered Wood Association – creates labels for every piece of lumber they certify, OSB or plywood. Probably, but the key is not to sheath using the minimum thickness. 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. Therefore, there are many options available. One of the difficult parts about figuring out roof coverings for your shed or house are all the options. 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. Drawings should be checked to verify the required spacing; closer spacing may be required at corners, edges, and ridges. Shingle and shake roofs may also be applied to solid sheathing at exposed eaves and rakes and similar locations. For plywood, which is slightly stronger than strand board, ½” thick is appropriate. o.c. The rafter spacing is 14"OC and unless there's a good reason to use 3/4. Make sure they are 1.5” long, which would work for ½” thick panels. 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. 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. Preformed metal roofing is lightweight and runs continuously in the direction of the rafters. 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. Save money by using a strand board, then use that savings to up the thickness a little bit. 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. Bracing may sometimes be omitted on hip roofs because the shape of the roof provides the bracing. o.c. The second number is the maximum o.c. Verify span with panel rating. Plywood particle board or wafer-board roof sheathing is most commonly used, being low in cost and easy to apply. Battens Over Solid Sheathing Improve Wood Roof Venting. Eugene has been a DIY enthusiast for most of his life and especially loves being creative while inspiring creativity in others. 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. Description - These are framing videos of an Oakland County Homes Near Birmingham which was designed and built by Hunter Roberts Homes. for shingles to 10 in. This can be done with a straight piece of lumber … The strand board, besides being cheaper, also works extremely well with tar paper. 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. Sagging roofs are very common – and visible – and are easily rectified at the time of install. This … 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. Less bowing means a more secure surface for roofing material, improving the longevity of your roof. However, it is considered good practice to leave a 1/8" gap between sheets, and that is … Standard roof sheathing thickness is ½” to ⅝” thick. 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. 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. for shakes. in wet weather conditions. Sheathing is installed once the roof structure is built. Rafters are spaced at wide centers since the decking will span more than 24 in. 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 Don’ts of Sheathing Your Roof. The second number is the maximum span when the panel is used for floor sheathing. 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. A panel marked 32/16 may be used for roof sheathing over supports spaced up to 32 inches o.c. 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. The span rating on FLOOR SPAN panels appears as a single Many metal roofing dealers specify minimum of 7/16" sheathing. Plywood dries much faster than OSB because it is not as dense. Use two clips for spans of 48 in. 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 RSRS designation 24” and 16” are the most common spacing, and you’ll often find 16” standard for rafters and 24” standard for trusses. This provides the full benefit of spaced sheathing on top of a solid roof deck. 30 felt underlayment, install vertical 2x battens lined up with the rafters beneath for solid nailing. Spacing Hint: Use a 10d box nail to gauge 1/8-inch spacing between panels. If you are using OSB for your roof deck, then ⅝” is the recommended thickness.