A 10d box nail can be used to gauge the ⅛" gap between panel ends. You will need to allow a 3mm gap between all the edges of the OSB deck to allow for thermal expansion and contraction. The roofing company and building inspector were both pleased with the gaping between the sheets. Figure 1. For that reason, any subfloor filler you use does not have to be particularly elastic. Avoid Butting OSB Panels Tightly. Where traffic is not a … In the past we have cut grooves into noisy GRP flat roofs, then backfilled with an expansion joint. This effect is covered in the design of the structure by using sufficient expansion gaps. Expansion gaps allow the boards to expand unrestricted before reaching the equilibrium moisture, which is likely to happen if the panels are not conditioned to the end-use climate before being installed. Is that OK and is it due to an expansion gap already being present in the T&G? If the gaps are filled, whether with sawdust, other debris, or an intentional sealant, then their ability to absorb expansion will be compromised. By the most conservative estimates of global OSB Sheathing market size (most likely outcome) will be a year-over-year revenue growth rate of XX% in 2020, from US$ 9588.7 million in 2019. or width. The builder has built a new side extension and we left the decking open ready to lay a new [...], This gives an idea as to what we were up against. This has certainly improved the situation, but reports back from customers have been fixed some have reported that the banging noise has gon away some say its got slightly better. You will need to allow a 3mm gap between all the edges of the OSB deck to allow for thermal expansion and contraction. Plywood and oriented strand board (OSB), like all wood products, will expand or shrink slightly with changes in moisture content. Ideally, gaps around penetrations are first sealed with tape on the outer side of the OSB, and then canned foam was sprayed from the inner side of the sheathing. This website uses cookies to improve your experience. or width. An expansion gap of 1/8 inch was used and the areas I felt were too tight I ran the skillsaw along the seam with the blade set at 3/4 inch. Expansion and contraction in OSB is not a problem (I think) As far a s I know, no gaps needed in 18mm T+G OSB the expansion is built-in. Nobody seems to know if this is because of how the boards have been fitted or if its because the GRP is too rigid. Good point, Tom. If the floor system is exposed to the elements and bulk water is present, sweep it … A permanently elastic expansion gap of 10mm provided every 10m of continuous sheathing (roof, wall). A 10d box nail can be used to gauge the ⅛" gap between panel ends. These spacing recommendations may not be adequate for buildings over 80' in length . We'll assume you're ok with this, but you can opt-out if you wish. HELPFUL HINTS FOR PROPER OSB INSTALLATION. we always leave a perimeter gape of 10 mm and push the bards together lightly; some never go tight as the edges are fragile and brake and bind. OSB and Ply gaps – Leave a 3mm gap between all edges of any 8 x 4 board If the roof is very large or unusually long, check that you don’t need expansion breaks as well. Use a 16d sinker nail for this purpose. The shaft of the nail is slightly larger than 1/8 inch. I would guess that OSB dries out from the face without the wax coating (to keep sheets from sticking to each other in manufacturing), and at the ends, edges. Step 1: Measure the board’s width. The expansion per meter if it gets damp is recorded at.03mm so it’s not much They constantly complain about the banging noise that comes from the contraction and expansion. Leave a 3 mm (1/8 inch) gap between the OSB panels to allow for expansion. Then as it dries out, shrinking, leaving gaps underneath for air to pass there. Also if I use normal boards, without the T&G and I put the 3mm expansion gap between all the boards, what happens over the joints when the rubber goes on. Install 23/32-inch or thicker OSB panels in the proper orientation, that is, with the side marked "This Side Down" facing down. Shop Blue Hawk Black 48-Pack Installation Spacers in the Laminate Flooring Accessories department at Lowe's.com. He has come across just about every type of flat roof in existence. Avoid Nailing or Stapling Edges of OSB Panels. Let panels dry before adding roof decking or siding. Ensure that the OSB panels are adequately spaced with the required 1/8” spacing at panel ends. Water does the most damage to OSB. See . Leave a gap of 1/32 inches between panels to accommodate the potential swelling of panels as their moisture content changes. Avoid Butting OSB Panels Tightly. We said it earlier, but it is worth repeating. That can mean costly, time-consuming callbacks. Ideally, gaps around penetrations are first sealed with tape on the outer side of the OSB, and then canned foam was sprayed from the inner side of the sheathing. Gaps between the sheets are specified by the manufacturer because the gap allows for a bit of movement - expansion, in particular - to be absorbed without causing any buckling in the roof deck. I know they are moving over to a new under T+G soon, but that’s all I know. OSB manufacturers require a 1/8-inch gap between the vertical panel joints to allow limited expansion of the panels. Subfloor materials including plywood, oriented strand board and, to a lesser degree, particleboard, are fairly stable, and any gaps that might develop between sheets are unlikely to widen. Know that wider boards expand and contract more than narrower ones. If the sheathing panels are butted flat together with no gap, the panels will not only buckle between the studs, but will crush along the edges causing a small ridge line. Stagger the panels over the roof with 2 supports between panel ends. Virtually every one recommends that you, your carpenter or builder create a 1/8 inch gap around all edges when installing plywood. Figure 1. If you have any questions or need any advice, feel free to drop a comment below and he will endeavour to reply. Save my name, e-mail, and website in this browser for the next time I comment. Here’s how to find them. Like any wood product, OSB will expand and contract after installation; without a small gap between panel ends, the expansion could cause buckling. I know they are moving over to a new under T+G soon, but that’s all I know. These spacing recommendations may not be adequate for buildings over 80' in length . tween 6-12%. Gaps between the sheets are specified by the manufacturer because the gap allows for a bit of movement - expansion, in particular - to be absorbed without causing any buckling in the roof deck. By sealing these seams, moisture, insects, dust and air can't permeate into a home. Installing without an expansion gap – Best practice is to leave a minimum of 1/8″ space between panels on the vertical and horizontal edges to allow them to expand. APA recommends a 1/8-inch space between panel edge and end joints. The lower part of the T+G this doesn’t meet the other side; however, the top use so I don’t understand how that works! For some premium subfloors, 1/16 inch may be enough along panel edges, so refer to the installation instructions. rogerk101, Oct 6, 2020 #3 Installing without an expansion gap – Best practice is to leave a minimum of 1/8″ space between panels on the vertical and horizontal edges to allow them to expand. An expansion gap of 2-3mm provided between all adjoining boards when fixing to supports; the gap must be continuous on all 4 edges of each panel, An expansion gap of 25mm left from the floor when fixing the boards to studwork, for wall sheathing. Recommended expansion gap is 2mm per metre run. See the recommendations for installing temporary Expansion Joints for Floors in Large Buildings on page 3. Video 2 of 3 on Liquid Rubber Flat Roofing, Video 1 of 3 on Liquid Rubber EPDM Flat Roofing Membrane, New Kemper Flat Roof in Shepherds Bush W12, New Flat Roofing – Kemper System Over Plastic Roof, What Can Happen if You Don’t Get the Vapour Barrier in the Correct Place. Required fields are marked *. Yes, in order to avoid dilation stress on the board edges. https://en.wikipedia.org/wiki/Oriented_strand_board. According to this latest study, the 2020 growth of OSB Sheathing will have significant change from previous year. If you have watched video 1, you would have seen the [...], Ply decking with torch on felt being applied over the top, ready for liquid rubber coating. OSB panels typically arrive to the jobsite at low moisture content (e.g., 5%). Blue Hawk expansion gap spacers are used to create a gap between the laminate or wood flooring and the wall before installing a wall base or quarter round. OSB comes in 4-by-8-foot sheets, as does plywood, but the manufacturing process allows the production of longer and wider ones. Expansion joints for commercial use are 0.2 to 0.3 inches wide and filled with permanently flexible filler like neoprene, urethane or polysulfide for flooring applications in high traffic areas (sealants in high traffic areas must have a shore hardness of 35). Most manufacturers recommend 1/8 inch at panel ends and edges. To avoid nail pops, pullouts, and shiners (nails that barely hit the joist), all of which … If you have any more questions, check out our decking guide or speak with … Photos of Insulation being laid over Old Decking. As any other wood product, OSB exhibits mild dimensional changes (shrinkage or dilatation in length/width) when exposed to changes in moisture and temperature of the surrounding environment. See the recommendations for installing temporary Expansion Joints for Floors in Large Buildings on page 3. Using T&G OSB this will not be possible. Although the roof is leaking and needs changing, [...], The roof has been stripped and the insulation has already been taken up the scaffolding, ready to go down. Especially if the studs, plates or OSB was damp or wet during/before construction. I’ve tried reading the BS EN 1995-1-1:2004+A1:2008 Eurocode 5: ( 145 pages but went to sleep), Tongue and groove do I leave expansion joints. An expansion gap of 1/8 inch was used and the areas I felt were too tight I ran the skillsaw along the seam with the blade set at 3/4 inch. internal partitions, door thresholds or pillars. Not Always Required But A Good Idea Box Gutter Being Lined With EPDM Single Ply Rubber, Parapet Wall Chimney Pots Being Dressed With EPDM Single Ply Rubber. It’s still unknown if an expansion joint was placed between the boards, would this still happen, theoretically the ridged GRP would hold the bards other solidly, so expansion or no expansion joint the area is still too big and solid. Steven has been working on London's flat roofs for over 30 years. Proper installation is H-clips provide additional stiffness between bearing points for the unsupported edges of wood panel (plywood or OSB) roof sheathing, along with the necessary 1/8” gap for expansion, as shown below illustrated on a bag of Simpson H-clips. I agree that they should be glued all round, but some of them clearly call for a 5mm expansion gap all round, so there you should only glue and screw to the rafters, leaving edges of each board to expand and contract as the weather and seasons change. Some older H-clips do not provide a built-in gap. If the expansion of the panel exceeds the provided gap, the panels are prone to … See . Letting Water Sit. Expansion gaps are narrow distances that must be provided at the panel joints when fixing the straight-edge OSB boards on supports. If the wood structural panels are tightly butted, there is no room for expansion and buckling can occur. APA recommends a 1/8-inchspace between panel edge and end joints. gaps the edges as the floor is assembled. Good question – I’m asked this all the time! Please consider the following factors: Do I need to leave expansion gaps with OSB? 5. When a roof is abutting a wall at the perimeter of the roof, allow 2mm per meter for the distance that the roof protrudes from the wall, for expansion purposes. Where the decking comes into contact with a wall allow a gap of 25mm. If the OSB is T&G all round then you don't have to join on a rafter. I’ve covered roofs over 100 m² and never had a problem, that said we don’t put rigid roofing material on the roof its normally rubber. [...], Liquid rubber being laid over ply and felt. Expansion gaps are narrow distances that must be provided at the panel joints when fixing the straight-edge OSB boards on supports. Where the decking comes into contact with a wall allow a gap of 25mm. Our specification for this new flat roof was [...], This is a skylight in an old three layer felt roof. Builders must allow ample space for OSB expansion and avoid buckling. Stagger the panels over the roof with 2 supports between panel ends. The lower part of the T+G this doesn’t meet the other side; however, the top use so I don’t understand how that works! Been reading that a 3mm expansion gap should be kept between the boards. Plywood used as a subfloor, wall underlayment or roof sheathing needs to have the seams sealed with caulk. If the gaps are filled, whether with sawdust, other debris, or an intentional sealant, then their ability to absorb expansion will be compromised. The usual practice is to leave this gap at the perimeter so it can be covered by skirting boards. London Flat Roofing. 154c Fleet Road, Hampstead, London NW3 2QX, Expansion and contraction in OSB is not a problem ( I think), As far as I know, no gaps needed in 18mm T+G OSB the expansion is built-in. It takes 36' (nine 4' panels, 8 gaps) of wall before the panel creep has moved a full inch, which is probably the absolute limit. A 2mm gap must also be provided at any abutments, i.e. Your e-mail address will not be published. Unsealed seams diminish the effectiveness of the cooling and heating systems of a home which can adversely affect utility costs. If you have any more questions, check out our decking guide or speak with … gaps the edges as the floor is assembled. The roofing company and building inspector were both pleased with the gaping between the sheets. Your e-mail address will not be published. 5. sheathing gaps for expansion RJT | Posted in Construction Techniques on September 5, 2003 05:53am If I leave an 1/8″ gap for expansion, I’d have to cut that much off each 4×8 otherwise before a couple of joists I’m off center. Keep a 1/8″ gap spacing between the roof panels and wall. When the sheets do expand and the gaps are filled with a hard filler there is no place for that filler to go but up. In my opinion gapping sheet goods then filling the gaps with a rigid filler especially concrete patch is just plain not the way to do it. Expansion gaps allow the boards to expand unrestricted before reaching the equilibrium moisture, which is likely to happen if the panels are not conditioned to the end-use climate before being installed. Luckily getting ahead of the material and calculating wood shrinkage and expansion is fairly easy – all you need to do is multiply three numbers together. When dry, I [...], What is EPDM Rubber? SMARTPLY OSB/3 • Panels junctions to be aligned centrally on timber stud framing • Screws to be inserted ≥ 10mm from panel edge • 3mm expansion joint to be left between all panel to panel connections • Equal gap maintained for full length of connections • … Using OSB. This gap allows for expansion due to changes in moisture conditions and … Avoid Nailing or Stapling Edges of OSB Panels. Failure to implement correct panel spacing may result in uneven flooring and buckling. Improper nailing. The intentional gapping is intended to allow for some expansion. If sheathing the wall starting with the first panel in the middle rather than at one end, it should be just possible to sheath a 36' length of wall without having to trim a panel to keep the end panels sufficiently over the studs for nailing. EPDM is a manmade rubber that [...], The Kemper system is laid wet into a fleece, as you can see we’ve even covered the internal surfaces [...], London Flat Roofing investigated a leak caused by two old joined leaking roofs of different materials – plastic and [...], One thing’s for sure, all the insulation on the roof will have to come out and we will have [...]. This gap will minimize or totally eliminate any puckering caused by swelling. Wood movement can ruin a seemingly well-constructed project. I get lots of complaints from people that have had GRP glass reinforced plastic flat roofs installed. If the sheathing panels are butted flat together with no gap, the panels will not only buckle between the studs, but will crush along the edges causing a small ridge line. Leave a span of 10 mm (3/8 inch) in from the edge of each panel when nailing or stapling to prevent fraying. Because OSB, like solid wood, will expand as its moisture content increases, it is recommended that the OSB panels be acclimated to their surrounding environment prior to in-stallation, or installed with a gap between panels to allow for expansion. Leave a span of 10 mm (3/8 inch) in from the edge of each panel when nailing or stapling to prevent fraying. Leave a 3 mm (1/8 inch) gap between the OSB panels to allow for expansion. From asphalt to zinc. OSB Expansion and contraction do I leave a gap.