The second method is to install the IronPly ® plywood underlayment with an expansion joint and using a seam filler. I am laying a new plywood subfloor onto existing joists using 8' x 4' sheets. Also, any tips on explaining this to my contractor? Sand all joints with a belt or floor sander until level and smooth. When installed with staples, the underlayment sheets are fastened every 2 inches along the edges of the sheet and every 4 inches in the field area. Malcolm, Also, what about the expansion gap around the perimetre of all laid areas. Moldings are needed to cover the expansion gaps along the walls, and when the floor edges transition to other floor coverings (carpet, tile, etc.) The distance of the gap can be maintained by inserting spacers made of off-cut timber. The second layer is there because I plan to tile the floor and want to minimise flex. You found a document that confirms it -- so thanks. Just as important is to make sure you have an adequate gap around the outside for the hardwood, follow … Thank you to everyone who has posted and responded to related questions and gotten me to the point where I can more or less ask this question in an intelligible manner. Virtually every one recommends that you, your carpenter or builder create a 1/8 inch gap around all edges when installing plywood. I suspected that was true for some brands of OSB and plywood, but was unable to confirm my hunch in my own search. I would prefer to butt each sheet against its neighbour and leave no gap. Not allowing the seam filler to dry sufficiently, Not sanding the seam filler smooth and even with the plywood underlayment, Too high moisture content in flooring environment, Placing the fasteners more than 1/2" from the edges of the panels, Inconsistent fastener depth and blow-through along the edges of the panels. I have a second story floor that was carpet over plywood subfloor. If this subflooring is going directly on joists use an adhesive like PL400 to glue it down, then either nail with ring shanked nails or screw it down to the joists. The gap itself will need to be around the whole perimeter of the room, including doorways, walls, fireplaces and radiator pipes. Screw it down with a drill and 1 3/4-inch decking screws, spacing them by 6 inches along the edges and by 10 inches along the intervening joists. • Offset panels edges from the subfloor edges by the minimum of 12”. The plywood goes down so the groove is away from the wall, that way, after the row is finished, or at least when you decide to start the next row, a 2X4 can be placed across the joists at the edge of the next row and drive, with a sledgehammer, the second run into the first. Thank you for responding, Malcolm. Do not oversand or "cup" the joints. * Note: You may leave an expansion joint without seam filler when IronPly® plywood underlayment is used under carpet, engineered floors, or wood floors. the thickness of a nickel, between each panel. Call Us (336) 299-7755 or Email Us for sales and technical information. I appreciate all the help. Stagger your joints by 1/2 sheet. For whatever reason, the contractor left gaps between each piece, 1/8" to 1/4" wide. That can mean costly, time-consuming callbacks. CoreLuxe is waterproof. Taping seams of tongue and groove sheathing,, Residential PV Installations in Florida Remain Strong. The contractor is opposed to taping the seams on the plywood because of expansion and contraction. 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. If so, how big should the gap be? The standard gap is 1/8". Mr. HandyAndy - Really Return to the starting corner and fasten the 4' edge at 2" on center - 1/2" from the edge of the panel. Do not force panels together, but do not leave a gap. An easy way to keep it consistent is to space the sheets with a common framing nail. Assuming that plywood expands and contracts enough to make this an issue (and please correct me on that if it is an incorrect assumption), should I leave a gap between the sheets of plywood to account for expansion and contraction? • Maintain a minimum 1/4” gap along all walls and vertical surfaces for expansion. The install instructions for Hardibacker call for a "dry-set" morter between the plywood and backerboard. Before moving or positioning any heavy object across the floor (such as a large appliance), place a minimum of 1/4" plywood on top of the completed floor to prevent point overloading. Leave an Expansion Gap Along the Walls. Do not "floor-mix" seam fillers on top of the. Improper nailing. Do not use any adhesive on the subfloor beneath, We recommend a pneumatic fastener tool that incorporates an adjustable depth-drive control to prevent fastener "blow-through" or "over-driving." Note that the same procedure is used as well for the offset sheet which would start the next row of underlayment. Cut plywood underlayment panels as necessary and lay out factory edges to factory edges. Use a 16d sinker nail for this purpose. Return to starting corner and fasten the "field" of the panel every 4" on center working in a diagonal direction across the face of the. If this feature is not available, adjust the air pressure on the compressor to an appropriate level to avoid fastener "over-driving" or "blow-through.". Leave a small gap between the underlayment and showers or tubs to avoid squeaks. Lightly butt plywood underlayment panel edges together. After sanding, the seam filler should fill the seams and be flush with the edges of the. Screws and nails may be spaced farther apart. Arrange the plywood on the floor so the joints of this layer do not align with the subfloor joints below. Stand on the panel to ensure flush contact with the structural subfloor and do not overdrive the fasteners. I am remodeling a 1920s colonial revival one-story, conventional foundation home in central Mississippi. Grip the top panel edge with one hand and firmly place the palm of your other hand against the face of the panel. Plywood used as a subfloor, wall underlayment or roof sheathing needs to have the seams sealed with caulk. Unsealed seams diminish the effectiveness of the cooling and heating systems of a home which can adversely affect utility costs. 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. He is a smart guy with lots of experience, and he cares about his work, but he does not like doing things differently than he normally does. Asked differently, the tape will maintain its grip even as there is expansion and contraction? Any "crackling" or "popping" noises indicate debris is underneath the panel. Leave a minimum gap of 1/4" and a maximum gap of 1/2" between the plywood underlayment panel edges and the walls for expansion. Anyhow, there are 8 joints about 20' long that I want to fill in. Do this by multiplying the room’s length by its width. After reading Martin’s article entitled Backyard Tape Test, I am considering Siga Wigluv, Pro Clima, and 3M tapes. Thoroughly vacuum the entire area to remove all debris before installing the floor covering. Thoroughly scrape, sweep, and vacuum the entire surface and strip any wax from the existing vinyl. Nothing to add, except expansion gap is not as crucial on ply as it is cross-bonded and is not as susceptible to expanding/contracting as natural grain wood. I understand I’m supposed to leave a 10mm expansion gap around the room edges of the plywood, but there is a tiled fireplace surround which won’t have skirting boards to cover up the expansion gap. Insert shims to create about a 1/4-inch to 3/8-inch gap between the flooring and the walls. Are holes in exterior plywood sheathing necessary? The plywood underlayment panels should be cut so that the factory edges go together at the seams in the field of the floor. Plywood and oriented strand board (OSB), like all wood products, will expand or shrink slightly with changes in moisture content. Select a corner of the room from which to start that is as square as possible, but leave expansion gaps of 10mm-15mm (about 1/2in) between the edge of the board and the skirting. The gap should be 1/8" between ends. Hopefully others will chime in. Some framers "creep" their layout to compensate. For that reason, any subfloor filler you use does not have to be particularly elastic. Joel, Much of the diagonal sheathing is still intact and in good shape, but for the master addition that is replacing an old 1960s add on, and for the garage (new slab on grade), we will be using plywood sheathing and Tyvek CommercialWrap D house wrap. 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. Fasten the 8' edge first at 2" on center - 1/2" from edge - starting from the corner of the room. joist spacing, single layer OSB or plywood subfloor Areas of Application over any even and structurally sound OSB or plywood subfloor with 16" (406 mm) o.c. You should leave a gap of between 12 – 15mm. For the subfloor, I am going to use two layers of 18mm (3/4 inch) plywood. The walls will be insulated with NuWool cellulose, and the siding will be Hardie Board. By sealing these seams, moisture, insects, dust and air can't permeate into a home. On a building this small, is it necessary to allow expansion gaps between the plywood sheets (I'm using 8' x 4' sheets so will use approx 2.5 sheets per layer) or can I just lay them tight? Before you install your plywood subfloor, first calculate the room’s square footage to find out how much flooring you’ll need to buy. The "plywood underlayment,subfloor sandwich" that you mentioned having to have the "movement joint" -you are talking about the second layer of plywood and not the sub floor, right? In our 50 plus years of experience, the majority of underlayment flooring failures are due to telegraphing seams and fastener blow-through. However, in the event of a flood or significant water leaks, the planks should be removed to allow the subfloor … Some cut 3/8" off every few panels - and some slam them tight and hope for the best. Plywood manufacturers are aware of these problems. Does the subfloor need the expansion joint as well? Once the panels are fastened, apply the seam filler and allow it to dry completely in accordance with the manufacturer's instructions. Sheets can be butted together (just touching, not forced tightly together) or they can be gapped about 1/8 inch, or so. • DO NOT four-corner fasten panel first. ... 16 inch on-center joist spacing with single layer OSB or plywood subfloor; ... Leave a 1/4″ gap between walls and the bathtub. This gap will minimize or totally eliminate any puckering caused by swelling. The key to a beautiful, long-lasting hardwood or laminate floor is a well-prepared subfloor. Hold this position during inspection. Return to the starting corner and fasten the diagonal at 4" on center to the opposing corner. Start from a panel corner and fasten row by row to the opposite side. Plywood underlayment panels should be laid in an offset pattern as shown in the Flooring Diagram so that four corners never directly intersect. My shop has 3/4" PT plywood for floor. 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. All structural panels/underlayment must be installed sealed-side down, and provide minimum 3/4" perimeter spacing. All fasteners should be slightly countersunk below the surface of the new underlayment. Fasten the remaining 4' edge 2" on center - 1/2" from the edge of the panel. In the rare instance that you find such an imperfection, do not use the panel. As for expansion gaps, since the floor is indoors and the material is plywood, you can use a 1/8 inch gap between the sheets with no problem. I understand that I should install a plywood layer over the original lay in order to enable the planks to be installed lengthwise. For a SurePly ® plywood underlayment installation without an expansion joint, lightly butt the panels together without applying any pressure so they barely touch at the joints.The second method is to install the SurePly ® plywood underlayment panel with an expansion joint and using a seam filler. Set it aside and contact Patriot Timber Products immediately for a resolution. Nick, Nothing short of physical plywood failure such as delamination will be warranted with regard to telegraphing seams. Ensure that the panels are installed with any grade stamps facing down to avoid the possibility of inks bleeding through the finished flooring. Begin by laying out the floor in a corner of the room where you can get the greatest amount of coverage without having to cut the. Become a GBA Prime member and get full access to GBA articles, enyclopedia, videos, CAD library, and more. Stand the panel vertically with its 4' edge on the floor and the panel face towards you (the staple/nail pattern will be facing you). As you install the pieces, move them away from the wall and tighten the joints out “in the field.” When the pieces fit and the joints are tight, tack them in place with a ring-shank nail or with the staple gun. Single layer of plywood or OSB Joists, I-joists, or trusses 16" (406 mm) o.c. To the best of my knowledge, based on many reports from the field, any one of the three tapes you listed -- Siga Wigluv, Pro Clima tape, or 3M All Weather flashing tape -- will be able to handle the small amount of expansion and contraction seen at sheathing joints. Subfloor is wood floorboards and and I’m going to put plywood boards down first to make sure floor is level. Please review these instructions to maximize the performance and appearance of your next flooring installation using IronPly® Premium Plywood Underlayment. Allow 1/4-inch gap along the walls and between the joints for expansion. If the wood structural panels are tightly butted, there is no room for expansion and buckling can occur. You must be a magazine subscriber to access this feature. These are the most common: Fastener blow-through is caused by not properly adjusting the drive depth or air pressure in your staple or nail gun, which can result in shooting the fastener completely through the underlayment. Joel, Square-edged or non tongue and grooved panels used as a subfloor will require a minimum 1/8" (3 mm) expansion space placed between all plywood seams. There are many factors that can cause telegraphing seams. Do carpenters have to shave off a bit from some sheets due to this? Store all panels on their 8' edge (separately if possible) to allow equal air flow over the face and back of the material. Thanks for the link to the LP specifications. These can be removed and the gaps filled in later with small strips of cork. I am expecting to receive my 11 rolls of Pro Clima Tascon Vana tomorrow. Not sure what's best to do? APA recommends a 1/8-inch space between panel edge and end joints. Leave an expansion joint of 1/8" to 1/4" between the panel and the edge of the walls. Allow all materials used in your flooring installation to acclimate to the heated home environment, approximately 70°F, for 24 to 48 hours prior to use. This won't delete the articles you've saved, just the list. Finish the sheet by fastening the remaining 8' edge 2" on center - 1/2" from the edge of the panel. Sorry, I only answered half your question - and I don't have enough experience with tape to answer the other half. Some additional application, drying time, and sanding may be necessary to smooth high or low spots. This reminds me of something I've wondered for a while... if the sheathing is exactly 4'x8' and the studs are spaced exactly 16" or 24" OC, then don't the 1/8" gaps accumulate after a few sheets and cause them to stop aligning with the center of the studs? They are not caused by panel failure. This feature has been temporarily disabled during the beta site preview. joist spacing interior dry or wet areas Limitations minimum 2" … If you do not leave an expansion gap, your floor will try to expand but will have no space, resulting in it warping or lifting up. If you choose to install the IronPly ® plywood underlayment with a seam filler, leave a 5/64" gap, approx. The floor joists run lengthwise to the room, and we want to install a floating laminate floor. Leave a gap of 1/32 inches between panels to accommodate the potential swelling of panels as their moisture content changes. To avoid nail pops, pullouts, and shiners (nails that barely hit the joist), all of which … Hand sanding is not sufficient. So the tape doesn't have a problem dealing with contraction and expansion? Not only that, but fixing down prevents this too. Definitely no gaps between sheets. Then fill the seams according to the seam filler manufacturer's instructions. ... To prevent that, you could cover the subfloor with a layer of 1/4-inch underlayment to raise the height of the entire floor. © 2020 The Taunton Press, Inc. All rights reserved. Right side up. • Use full body weight over the area with the subfloor. 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. Unfortunately, the APA video (below) doesn't answer the stud-spacing question. Stand on each plywood underlayment panel during fastening to ensure full contact with the subfloor. Allow sufficient curing time to completely dry the seam filler. Telegraphing seams and fastener blow-through are always the result of incorrect installation. With the plywood underlayment panel in this flexed position, thoroughly inspect the entire panel surface for imperfections, which will look like "bubbles" or "creases." Probably because this part of the house is in the 100 yr floor plain. Pull the panel down approximately 4” - 8" with your top hand while simultaneously pressing forward with the palm of your other hand approximately 4” - 8" until a noticeable curve is in the panel. Hand cut exterior edges for installation next to the walls. Probably the best way to explain it to your contractor is to tell him it's the recommendation of the APA and most building codes. For full dimension sheet goods there a number of strategies. On the flat ends, you can use a 1/8" gap to take into consideration expansion and contraction. FAQ: Why Do Some Builders Avoid Foam Insulation. Flooring contractors and installers depend on IronPly® Premium Plywood Underlayment from Patriot Timber Products for its consistent quality, durability, and dependability. Would a 2mm expansion gap be best around each board to allow for plywood expansion? Patriot Timber Products, Inc.117 S Westgate DriveGreensboro, NC 27407Fax: 336-299-4050, Better Alternative than Lauan and Meranti Plywood, Meranti Plywood / Lauan / Luan vs. RevolutionPly®. Most sheathing panels now come 1/8" undersized. Install DITRA on a Wood Subfloor (stop Cracked Tiles): Cracked floor tiles stink…REALLY BADThere’s a simple solution: DITRA It goes down on top of wood or concrete subfloors. Thanks Martin and Malcom. Should this occur, stop the installation, remove and discard the panel, then scrape, sweep, and vacuum the subfloor again until all debris is removed.