See our complete plywood underlayment installation video at www.InstallSurePly.com. For many years, the standard option was lauan plywood, also called Philippine mahogany or luan plywood, which is made with an inexpensive tropical hardwood, and therein lies its problem. For optimal and long-lasting results, consider all three components when installing a new floor. Plywood continuous over two or more spans and face grain perpendicular to supports.Unsupported edges shall be tongue-and-groove or blocked except where nominal 1 / 4-inch-thick wood panel-type underlayment, fiber-cement underlayment or 3 / 4-inch wood finish floor is used.Fiber-cement underlayment shall comply with ASTM C1288 or ISO 8336 Category C. Allowable uniform live load at … For touch-sanded grades such as C-D Plugged, C-C Plugged, UNDERLAYMENT and APA RATED STURD-I-FLOOR (marked PS 1), see Table 2. This will be necessary if you're going to lay down resilient (vinyl) flooring. The addtional underlayment should be glued and screwed down over 3/4 inch thick OSB subfloor to add stability. Do I need to remedy my subfloor before I put down carpet? The sheets are generally 4 x 8 or 4 x 12 feet in size. Sturd-I-Floor® is an APA designation that is a combination subfloor-underlayment produced from OSB or plywood. 1/4" plywood does not add structural integrity to a floor application and does not have the nail holding capacity. A conventional subfloor includes 2×4 sleepers, vapour barrier, 1″-2″ rigid insulation, 15/32″ plywood, and a lot of fastening. The thickness needed for subflooring depends on the type of floor that will go on top and the primary purpose for the subfloor. The two layers together made up the subfloor. The span rating for 1/2 inch plywood is 32/16. I am about to lay 1/2" APA Underlayment rated plywood down as an underlayment over 3/4" plywood subfloor for 1/2 strand woven bamboo. Plywood comes in a variety of thicknesses, beginning at 1/8 inch and increasing to 1 inch. If you intend to put down carpet or hardwood flooring, that won't be necessary. For the plywood, I’d need four 4’x8’ sheets total, and I should have a 4’x2’ piece left over. Removed this floor down to the joists and replaced the 1/2" plywood :bonk: . A 3/4 inch sheet of plywood weighs approximately 75 lbs. Removed all original flooring down to the 1/2" subfloor. 10 Posts . Be careful! This resulted in a ton of edge swell. The right type of plywood for your bathroom's subfloor will vary based on the type of floor you are placing over it. Steps to Install 3/4 Inch Plywood Subfloor. Had water damage under the halfbath floor (1" mudbed). Forgetting to check your work. It was 1-1/8-inch plywood we should have glued to framing but just nailed it. Direction As a sub-floor, I prefer to install the plywood sideways as the finish flooring will be installed lengthwise on top of that. It typically comes in 4 x 8-foot sheets. 16 inch on-center joist spacing with single layer OSB or plywood subfloor; 19.2 inch on-center joist spacing with single layer OSB or plywood subfloors; 24 inch on-center joist spacing with double layer OSB or plywood subfloors; 24 inch on-center joist spacing with single layer OSB or plywood subfloors; Each configuration has specific guidance for: That’s 32” when plywood is sheathing for a roof (not much expected weight on it), and 16 inches as a floor (lots of expected weight on it). Plywood comes in 4-by-8-foot sheets with thicknesses ranging from 1/4 to 1 1/4 inches. Resultant finished height (5/8" + 1/4") does not equate the same strength as a solid piece of material at the stated thickness. Filled a 20 yard dumspter. BTW, 1/2 + 1/4" does NOT equal 3/4", strength wise. Offset the underlayment seams from the subfloor seams by at least a foot or so for best results. Most plywood underlayment is about 1/4 inch thick and has square edges and a smooth, knot-free top face. 9. Assuming a remodel, this is going to involve bringing the plywood to the location by hand, as opposed to assistance by a crane. • Glue-down subfloor: 5/8 -inch plywood panels are glued in a staggered joint pattern directly to the slab. Step 1: Get the plywood to the right level of the house. For hardwood, tongue-and-groove CDX plywood rated AC with a 1/2- to 3/4-inch thickness is ideal; ceramic or porcelain tile does best with 3/4-inch AC plywood; and stone should use 19/32-inch tongue-and-groove plywood. The fasteners should not protrude out of the bottom side of the subfloor. Some people have told me it is not needed, but I want more opinions. When installing engineered, solid or floating floors that are less than 1/2" thick we highly recommended you add an additional layer of 3/8" or 1/2" thick plywood underlayment. The panels should be staggered every 2 feet and spaced 1/8 inch between ends. This provided a nice stiff floor and eliminated my squeak issues. The half inch (actually 15/32 inch) thick plywood that I use, adds another 73.5 lbs to the conversion. I have 1/2 CDX plywood subfloor. Re: 1/2" plywood subfloor Nearly every house I framed in the 70s and early 80s was 1/2" subfloor with 5/8 particle board over in the carpet areas and 5/8" ULCX ply at the vinyl areas. I have 3/4 inch thick plywood screwed to joists already and I am going to add secondary 1/2'' plywood underlayment on top of it for more stiffness because I am going to tile marble floors. Prior to finished floor installation, walk the subfloor to check for squeaks, missing fasteners, improper nailing, etc. The uncoupling membrane is adhered to the surface being tiled using a layer of thinset adhesive applied with a 1/4-inch V-notch trowel. Plywood, or even OSB, has its strength running with its length. The system is designed for use on all of the most commonly used subfloor materials—plywood, OSB, concrete and gypsum-based screed. • Nail-down subfloor: 5/8 -inch or thicker plywood panels are fastened every 12 … Place your plywood pieces so their joints don’t go directly over the joints of your wood subfloor. It is fastened to the subfloor and sits below the finished floor, providing a suitable base that is as smooth and flat as possible. The combined height is between 2-1/4″ and 5-1/4″ compared to 1″ for a DRICORE ® Subfloor R+ panel. A single 1/2" alone isn't good enough regardless of the finish flooring you choose, with the exception of hardwood. I'm going to install tiger wood 3/4 inch hardwood floors in my house. Plywood is the most common type of subflooring. 1-1/8 x 4 x 8 Sturd-I-Floor Tongue & Groove OSB Subfloor (Actual Size 1.069" x 47-1/2" x 95-7/8") Model Number: 1242922 Menards ® SKU: 1242922 Installed 16 sheets (very pricey) of 3/4" sanded plywood directly over the 1/2" subfloor. The floor system is not dependant upon receiving any strength from the hardwood floor to meet this requirement. Additionally as mentioned, drywall screws are not rated for flooring application. However, on one of my very first houses using plywood, we had a giant downpour during construction when the frame was open. Leave a 1/4-inch expansion gap around walls and joints. Step 3: Secure your plywood pieces in place using 1-inch decking screws. Flooring underlayment comes in a variety of different forms, ranging from 1/4-inch plywood to cement board to carpet padding or foam material. Subfloor plywood is extremely strong and can support most floor types including plywood and treated plywood. We’re comfortable slightly exceeding the recommended subfloor spacing. These panels feature a built-in underlayment that allows the convenience of using only Sturd-I-Floor® under certain finish flooring, especially carpet and pad. I am thinking #8 length 1-1/4 inch, but I am really not sure. Table 1 applies to unsanded plywood and is based on APA RATED SHEATH-ING (marked PS 1) grade. Table 3 applies to sanded grades such as A-D and B-D. Do not 1/4 turn the underlayment direction from the subfloor. What size number and length of screws should I use to screw 1/2 plywood underlayment to subfloor? For best results, you'd then apply 1/4 inch lauan underlayment plywood over the repaired subfloor to make it perfectly level. Used 3 boxes of 1 5/8" Deckmate screws. Exposure 1 : Plywood suitable for uses not permanently exposed to the weather. If additional force is needed, always use a block of wood against the groove edge to minimize damage to the panel, and always allow a 1/8-inch gap between panels. When your house was built the subfloor system was 1/2" ply with 5/8" (probably) over it. Make sure you predrill the hole through the 1/4 inch plywood, use a bit the same diameter as the outside thread of the screw. 4 x $40 = $160. Foolishly, the tile guys wanted to mud base over just the 1/2" so the tile wasn't so much higher tha the hallway and bedroom carpets. Hide screw heads below the surface of your plywood pieces to … For screws, a 1 lbs pack of 3 inches long #8 coated screws will cost around $10, I’ll use these for the framing. Panels classified as Exposure 1 are intended to resist the effects of moisture on structural performance as may occur due to construction delays, or other conditions of similar severity. Is the extra 1/4 inch really needed? The manual says you need 3/4 inch CDX plywood subfloor. A plywood subfloor generally uses 1/2-inch to 3/4-inch-thick sheets of plywood that have one rough side (which faces down) and one smooth side, which faces up. I could just have well been parquet. Additionally, underlayment plywood is a middle layer that keeps moisture from reaching the surface. Re: 1/2" SUBFLOOR Bill, If the joist are ok and the 1/2 plywood subfloor is rated 16/32 which it probably is, the it meets the minimum requirements of the code. It should not be so long that it penetrates the combined thickness of the plywood underlayment and subfloor. Tags: installing plywood underlayment, plywood underlayment Your new layer of underlayment needs to be perpendicular to the joists just like the subfloor is. Answer. 3/4 inch pressure treated CDX goes for about $40 each where I am. Discussion Starter • #1 • Apr 25, 2012. If you are using 1/4 inch plywood, and you are going through 3/4 inch subfloor, I would go with a 1-1/2 to 2 inch screw. 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