The costs of building materials continue to rise and environmental concerns make some products less desirable. If you’re building a home, cottage, cabin, shed, garage, or other structure, consider T1-11 siding installation. It looks like board and batten siding, so provides the outside finish, plus it saves on the sheathing cost in both materials and labor since it is sheathing as well.
T1-11 siding installation is easy. Wrap and staple Type-1 tar paper or house wrap to 16” o.c. framing and cut window and door openings with a utility knife. Fasten the T1-11 siding to the studs with galvanized nails or exterior grade screws. Use a router or saw to cut openings, and finish it with a good quality stain or paint.
In this guide, we explain what T1-11 siding is, some pros and cons, and whether it should be installed over Tyvek or plywood. We also discuss the type of fasteners to use, what pattern, and where, plus a step-by-step guide for installation. Additionally, we look at whether T1-11 panels can be installed horizontally, the cost of T1-11 siding, some problems you might encounter, and some alternatives to consider. All the best on your project!
- What Is T1-11 Siding?
- T1-11 Siding Pros and Cons
- Do I Need Tyvek Under T1-11 Siding?
- Do You Need Plywood Under T1-11 Siding?
- Is It Better to Screw or Nail T1-11 Panels?
- Do You Nail T1-11 in the Grooves?
- T1-11 Siding Nailing Pattern
- T1-11 Siding Installation
- How Do You Install T1-11 Plywood Siding on a Shed?
- Can You Install T1-11 Panels Horizontally?
- T1-11 Siding Installation Cost
- T1-11 Siding Problems
- T1-11 Alternatives
What Is T1-11 Siding?
T1-11 siding is an engineered all-wood panel that has been around since the 1960s. It was the go-to choice for home siding into the 80s until it was displaced by vinyl siding and other composite options. Although T1-11 is rated for 20-years, it’s still going strong on many of the early structures it was used on. T-1 continues to be used and is available at most wood stores and home centers.
T1-11 siding is structural 4×8 or 4×10 exterior wood panels that have one side textured with grooves or channels, hence T1. The textured side may be sanded smooth with the grooves or roughly textured with grooves for a more rustic look and feel. The grooves are typically 4” or 8” apart and cut into the outer wood layers. The panels come in 3/8”, 5/8”, and 3/4” thicknesses of plywood or OSB (Oriented Strand Board).
The plywood is made of thin layers of veneer glued together under high pressure and heat to fuse the layers. OSB is made of wood strands soaked in resin glue and arranged in alternating layers which are then heated and pressed to fuse them into a panel or sheet of wood. Once fused together, both types of panels are trimmed to size, and the grooves cut before being sanded.
T1-11 Siding Pros and Cons
Like any siding or product, there are pros and cons to consider. T1-11 isn’t without its share of both, however, if it is properly maintained – like most anything – it will last for years. The truth be told, in many exterior home applications, it has already lasted for 30 to 50 plus years.
T1-11 plywood or OSB siding panels are made in North America from a renewable product – wood – making them more eco-friendly than other siding choices. The multilayers make it lighter than solid wood, stronger than wood of the same thickness, and more resistant to cracking or splitting too. The large 4×8 or 4×10 foot sheets are easy to transport, work with, install, and they cover 32 to 40 square feet in one piece. Plus, they’re less expensive than other siding options!
T-1 siding is available in board-and-batten and shiplap profiles and can be stained or painted any color, or sealed and left natural. The panels are flexible, so can follow curved surfaces, have a natural wood grain, and can be cut, trimmed, and oriented in different ways for a variety of looks. Cut-offs and leftover siding can be used for other projects, recycled, or chipped into compost.
Whether you’re a DIYer or pro, T1-11 siding offers a quick, easy, and inexpensive way to sheath and side homes or outbuildings. Wood won’t fade, dent, or mark like plastic, vinyl, or metal sidings, and offers a smaller carbon footprint too. Properly maintained and stained every 3 to 5 years, or painted with a quality exterior paint every 10 to 15 years, it can last a lifetime.
Proper maintenance, however, is a necessity. Untreated wood is susceptible to moisture damage and rot, so it is necessary to reapply stain, sealer, or paint on a regular schedule. Additionally, unlike steel, aluminum, or stucco, wood is flammable and susceptible to insect damage, but it won’t melt or give off poisonous fumes like plastics or vinyl. Cuts and joints also need to be sealed or treated to prevent swelling, flaking, or layer separation, which can add to the installation time.
Do I Need Tyvek Under T1-11 Siding?T1-11 is both a siding and a sheathing and can be fastened directly to the exterior face of the studs. House wrap like Tyvek or tar paper provides a wind and moisture barrier which can be beneficial depending on the purpose of the structure it is used on. The big concern is that the wrap can be damaged while awaiting the T1 panel installation.
Tyvek is a wind and moisture or weather barrier but is permeable to water vapor, so it will allow the vapor to move through. A good rule of thumb when deciding on whether to use Tyvek or another house wrap is: If the structure will be heated or air-conditioned, it should be wrapped. The wrap helps to keep the weather out while allowing interior water vapor generated from showers and cooking to escape.
It is always recommended to check the local building codes. The IRC (International Residential Building Code) addresses both water resistance (R703.1.1) and wind resistance (R703.1.2) barrier requirements. Under IRC-2021, a continuous water-resistive barrier (R703.2) is now required over the studs or sheathing, so it is under the exterior wall covering.
Do You Need Plywood Under T1-11 Siding?
Structurally rated 7/16” or thicker T1-11 siding can be fastened directly to the exterior face of studs at 16” centers and can act as both sheathing and siding in one. T1-11 siding 3/8” or less in thickness isn’t rated as structural and will require sheathing underneath it. The purpose of the structure and its location, though, may be a determining factor on whether to use plywood underneath T1-11 panels.
It is best to check the local building code to determine if plywood sheathing is required. Even though it may not be considered necessary, many builders feel it is best to use plywood under T1 siding if the structure will be used for human habitation. All joints and seams need to occur at studs or horizontal bracing or plates to ensure there is solid backing. Having plywood under T1-11 allows for greater seam and joint placement flexibility and support too.
Is It Better to Screw or Nail T1-11 Panels?
The decision to use nails or screws to fasten T1-11 siding often comes down to preference. Some do everything with nails and others only use screws. Nails are more difficult to remove than screws, but once installed, T1 should last for decades if properly maintained and shouldn’t need to be replaced. An added bonus with T1 is that it acts as both sheathing and siding, so if you get tired of the maintenance and look, you can just cover it with a different siding.
Attaching T1-11 to studs at 16 o.c. should be done with hot-dipped or electro-galvanized nails or other approved and treated fasteners. Galvanized or treated fasteners prevent corrosion which can lead to rot and other issues. Stainless steel is even better but more expensive. Some building codes, though, require stainless steel fasteners to be used within 15 to 50 miles of bodies of salt water to prevent corrosion.
The IRC-2021 recommends a minimum of 2”x0.099” (6d) siding nails be used to fasten exterior grade 3/8” to 1/2″ wood structural panels like T1-11. It further requires that the fasteners penetrate at least 1-1/2” into the stud, so T1 panels thicker than 1/2″ would require longer 2-1/2” or 8D nails. It is important to note that the building codes set the minimal requirements, which means fasteners with greater substance or length are acceptable too.
Box nails and common nails would work too, but large heads will show up more, and thicker nails can split wood near the edges. Ring and spiral-shank nails have excellent holding power and are a good alternative.
Nail guns with coils or strips of nails can be used to fasten T1 panels, however, the collating plastic, paper, or metal can become caught and need to be picked out of the wood. Additionally, the nail gun may drive the head into the wood and require filling to hide and protect exposed wood. Loose nails may take longer initially but are less expensive, so pick which works best for you.
Exterior grade or treated screws can be used to fasten T1-11 panels provided they meet the minimum code requirements. A #8 1-7/8” screw is equivalent to a 6d nail, and #8 2-1/2” screws are an alternative to 8D nails. The problem with using screws is that they are thicker than nails, have larger heads that are more visible, and the head needs to be set into the wood, which can cause it to split. Plus, screws take longer to drive and are more expensive than nails.
Despite the problems with screws though, many contractors prefer screws over nails to secure T1-11 panels in place. The screws are easier to control, pull the panel tighter to the studs or sub-sheathing, and are easier to remove if necessary. Additionally, decking screws come in several different colors which may blend better with the desired wall finish.
Do You Nail T1-11 in the Grooves?
Some T1-11 panels are milled to have a shiplap on the long edge, which means the edge of one sheet will overlap the edge of the adjacent panel. Other panels are designed to be butt joined on the long side. T1 can also have several different profiles with grooves spaced every 4”, 6”, 8”, or even 12” apart.
When nailing or screwing T1-11 panels to studs spaced 16” o.c., the location of the groove may or may not align with a stud. The shiplap edge is the same thickness as the groove, so it is acceptable to fasten into the grooves if they align with the stud, otherwise, nail or screw through the thicker wood where it rests against a stud. Setting a nail flush with the base of the groove, however, may be difficult and require a nail-set, so using screws may prove easier.
T1-11 Siding Nailing Pattern
The typical nailing pattern for T1-11 siding is similar to that of fastening any type of plywood panel. Every 6” on the sides and every 12” on the studs located in between, the edges at the sill and top plate should be nailed every 4” to seal tight against insects and air.
On ship-lapped edges, some prefer nailing the overlapped edge seam once the two panels are in place. It reduces the number of nails going into the bottom piece’s edge and still provides solid fastening.
T1-11 Siding Installation
T1-11 siding is made of wood and will provide a wood-look and finish to any structure. Like any wood though, it should not be installed where it will touch the ground. Additionally, plants, shrubs, and other vegetation should be kept at least a foot away from the wood so it can breathe and dry.
T1 panels come in 4×8 and 4×10 foot sheets in standard thicknesses of 3/8”, 5/8”, and 3/4”. There may be other thicknesses available depending on your location. Thin sheets typically are used over another sheathing, or for small structures like dog houses. The thicker 5/8” and 3/4” panels are used to sheath and side homes, cabins, shed, garages, and other structures.
Pro Note: Structures used for human habitation or with an HVAC system should be wrapped with a moisture barrier such as Tyvek prior to installing T1-11 sheathing and siding.
Depending on the stud spacing and the wall height, the edges of the T1 should align with and fasten to studs, top plate, and cover the sill or bottom plate. The type of T1, the size of the structure, elevations above the ground, and help available all affect installation.
When working alone, I’ve often fastened a temporary 2×4 to the rim plate to support the bottom of the plywood sheet at the correct height so I can place and fasten it more easily.
Here are the typical steps to fastening T1-11 siding to a stud structure framed at 16” centers.
Select the size of T1 paneling that will best fit the wall height. The bottom should cover the sill plate and if possible, overlap the rim joist or foundation by 1/4″ to 1/2” to cover the seam. If there is an exposed sub-floor edge, it too should be covered. Wall heights of 8’ to 10’ can be covered with one sheet, taller walls will need a seam and require backing for nailing where the upper panels meet the lower ones.
Select the fasteners you prefer. Whether 8D nails or #8 screws, they should be long enough to penetrate 1-1/2” into the studs and be galvanized or coated to prevent corrosion. Make sure you have enough to do the job too.
Mark the location of all studs on the top plate and rim plate or foundation so they are easier to find once the plywood is in place.
Depending on the wall height to be covered and the length of the T1-11 being used, the length may need to be trimmed. Trim one sheet and ensure it fits prior to cutting more. Only cut what you need, as once cut, it can’t be returned.
Start at a corner. Orient the panel so the outside shiplap (if the long edges are lapped) is flush with the edge of the corner stud. Align the bottom so it covers as mentioned in Step 1.
The outer edge should align with the center of a stud 4’ from the corner. If it doesn’t, move the panel back toward the corner until it does, and mark the sheet at the corner for cutting, and cut. Alternatively, check the stud spacing at another corner and start there.
Once you know it will fit, place and hold the first sheet against the studs. Drive a nail or screw about 1/2″ to 3/4″ down from the center top edge of the panel and into the top plate, so it is tacked in place.
Check the alignment of the panel edges. Back out the screw or nail and adjust if necessary. Once aligned, fasten the corner edge every 8”. Use a string or chalk line or another straight edge to identify where the next stud is using the marks on the top and rim plates. Nail the panel to the middle studs every 12” from top to bottom or bottom to top. Screws or nails should be driven flush with the wood panel surface.
Leave the outside stud edge unnailed if it is shiplapped, otherwise, fasten it every 8”.
Nail or screw the top and bottom edges every 4”. Keep the fasteners 1/2″ to 3/4″ from the panel edges.
Place the next T1 panel in place so the edge butts tight to the previous one, or the outside lap overlays the inside one. Align the top and bottom, and ensure the outside edge centers on a stud. Tack it into place as in Step 3. Some pros recommend caulking the lap joint prior to fastening it, so you may wish to do so. Then fasten as in Steps 4 and 5.
Repeat Steps 3 through 6 until the structure is sheathed and sided.
Once everything is installed, treat or seal all cut edges and the exposed surface to prevent moisture damage.
Pro Note: Window, door, and other openings can be cut out prior to fastening or once the sheets are installed using a sawzall, router, or another device. Ensure the edges of the openings are fastened every 4” to 6”.
How Do You Install T1-11 Plywood Siding on a Shed?
T1-11 siding can be nailed directly to the studs of the shed framework and act as both sheathing and siding. Start at a corner, align the first sheet with the edge at the corner and the other edge centered on a stud. The top should cover all or half the top plate depending on the structure’s elevations, and the bottom covering the sill or bottom plate and any exposed subfloor edge.
Using treated 8D nails or #8 deck screws of the appropriate length, fasten the panel sides to the studs every 6” and the inside to the studs every 12”. The top and bottom should be fastened every 4”. To prevent rot and mildew, the plywood should be installed so it will not touch the ground. Follow the 7 Steps above to install T1-11 siding on a shed.
Can You Install T1-11 Panels Horizontally?
Modern shiplap T1-11 siding can be installed vertically or horizontally. The inside layers of current T1 plywood have no open voids that can be exposed when the grooves are milled. So, once sealed, stained, or painted, moisture won’t find pockets or openings between layers exposed by the grooves.
Panels are 8’ or 10’ long, and the upper layer lap covers over the lower layer lap, helping to seal out the weather. The butt ends of the panels should be caulked or sealed to prevent moisture damage, and are also often covered with 1-by strapping for additional protection.
Depending on the climate and roof overhang, horizontally applied T1-11 may require more frequent maintenance and reapplication of stain or paint. With proper care though, horizontally aligned T1-11 panels will last for decades. Before installing, check with the local building department for any restrictions.
T1-11 Siding Installation Cost
A 4×8 sheet of T1-11 plywood will vary in price depending on the type (plywood vs OSB), thickness (3/8” to 3/4″), profile, shiplap or not, and finish, with prices ranging from $34 to $56 USD. The size, shape, and elevations of the structure also will impact the cost of materials. Installation often includes labor plus nails or screws, trim, and flashing. However, if you’re doing the work yourself, you’ll save 50% to 80% of what a pro would charge for the job.
To determine the base cost of T1-11, measure the perimeter of the structure and multiply it by the height for the square footage to be covered. Divide that value by 32 (the area one 4×8 sheet covers). Round up and that’s the number of sheets required.
A 24’x36’ cabin with a hip roof (no gable ends) has a perimeter of 120’. Multiplied by a wall height of 8’, and that’s 960sqft. Divide that by 32, and you’ll need 30 full sheets. If we pick $40 for the cost of our T1-11, that’s $1,200 for the plywood alone. Screws or nails plus any flashing adds between $20 and $200 for a max of $1,400.
While the cost of materials may be $1,400 or $1.46 a square foot if you do it yourself, most contractors charge by the hour or job. It’s their labor cost that will hurt, hence, if you can do it yourself, you save a lot.
Hiring someone to do the work can add between $2.00 and $5.75 or more a square foot to the material costs, so between $3.50 and $7.25 a square foot for materials and installation. This means siding that little cabin in our example with T1-11 would cost between $3,360 and $6,960 if handled by a pro.
T1-11 Siding Problems
As with any siding, T1-11 does have its share of problems. Its greatest weakness is its susceptibility to moisture damage which can cause swelling, flaking, layer separation, warping, mold, mildew, and rot. However, proper installation, care, regular maintenance, and the use of a good quality paint every 10 to 15 years or stain every 3 to 5, can protect T1 from moisture. If you want maintenance free though, don’t pick T1-11.
Some other T1-11 problems are related to all wood products. Splinters and chipping can occur at cuts during installation but can be sanded and sealed with paint or stain. Plywood and OSB both contain resins or glues which produce off-gassing that may be irritating to some.
Termites and carpenter ants can also be an issue too, depending on your location. Last but not least, wood is flammable, so you may wish to choose a less flammable siding if you live in an area susceptible to wildfires.
Alternatives to T1-11 siding depend on what you are looking for, personal preference, and budget. You could choose vinyl, plastic, aluminum, or steel siding, stucco, brick, or stone, all of which are commonly installed over plywood sheathing. If you don’t want those options, but want a natural and renewable siding and sheathing all-in-one like T1-11, there are some choices.
One option is using exterior grade plywood to sheath the structure. Once sheathed, fasten 1×2 furring strips or strips ripped from 2-by material vertically to the plywood covered wall. The strips can be spaced every 6”, 8”, or 10”. They could even be lined up with the studs adding protection to the screws or nail holding the sheathing in place, and an intermediate strip placed equidistant between to give a board and batten appearance.
LP SmartSide is another choice. An OSB plywood with a similar profile to T1-11, but with the addition of a protective outer coating. SmartSide is also chemically treated to resist insects, including termites. It requires less maintenance than T1-11 or the previous option.
A final option is HardieBoard or HardiePanel vertical siding. It’s made of cement, sand, and wood or cellulose fibers and finished in different wood-look profiles, including one like T1. Installation is similar to other wood panels. Due to its composition though, it is more resistant to moisture, fire, insects, and requires less maintenance than T1 or the other alternatives – it is also, however, more expensive.
T1-11 siding is easy to install for the DIYer or pro and can be used as an all-in-one sheathing and siding for homes, garages, cabins, sheds, and even the dog house. When used for structures that will be heated or cooled, a moisture barrier should be stapled to the stud framework prior to installing T1.
To protect the wood siding from moisture and insect damage, it should be sealed, stained, or painted with a good quality product and regularly maintained. Hopefully, you have a better understanding of the installation process for T1-11 siding and are ready for your project.