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Why T1-11 Siding Sucks

Rotten T1-11 siding

If you’ve ever been to the sheetgoods section of a big box store you’ve probably seen the sheets of T1-11 siding lurking about. This bargain basement siding has been ubiquitous on cheap remodels and “budget friendly” structures for years.

To be clear my issues with T1-11 siding don’t come from a snooty, greater than thou, point of view. Rather, my issues come based on basic building science. Let me explain below the issues with this atrocious form of siding and why you should stay away from it at all costs.

What is T1-11 Siding?

T1-11 siding

Sometimes referred to simply as “plywood siding”, T1-11 siding is sold in 3/4” thick 4’x8’ sheets. It comes in a plywood version which is bad and an OSB version which is even worse. They come with a 3/8” lap joint on the sides so that each sheet can be tied into the next sheet and keep water from entering the wall structure.

One of the reasons this siding has been some popular is because it is soooooo cheap. At the time of this writing you can get a sheet of T1-11 siding for only $38. Since the sheet is 32 SF you can side a whole building for $1.18 per SF which is far cheaper than almost any other option on the market. Not to mention that installation is extremely fast so that keeps labor costs down below most other wood sidings.

T1-11 siding is typically installed vertically to give a look reminiscent of board and batten siding, but it can be install horizontally though that is rarely done.

What is the Problem with T1-11 Siding?

It’s really pretty simple why I’m diametrically opposed to T1-11 siding, it’s called building science. On most structures we use plywood or OSB as sheathing and cover it with building wrap to protect it from the elements. Major damage can occur to this sheathing if the building wrap is applied improperly or if water gets through the exterior cladding so we take great strides to protect it from exposure.

Problem #1 Exposure

With T1-11 siding, which is made the same way as these plywood and OSB sheathings we leave it exposed. It’s the same wood that is prone to the same damage if exposed to the elements, yet with T1-11 siding we proudly display our plywood or OSB siding to the elements. Yes we paint it, but that is the only protection we provide.

Thin strands of wood held together by glue and other binders are left exposed to the elements to degrade as they inevitably will. Rather than installing plywood sheathing, building wrap, and wood siding builders using T1-11 essentially stop at the sheathing point and paint it. Not a good idea if you want siding that lasts.

Problem #2 Edges Issues

Whether you are using the plywood or OSB versions of T1-11 the edges are almost always a problem. OSB has been shown to have a high moisture absorption rate on its edges after being installed. And plywood, just like any wood, pulls moisture into its end grain like water through a straw. The basic design of wood is to facilitate waters movement up through its structure to feed the tree. So end grain is very good at drawing water up into the body of the wood just like when that plywood was a living tree.

This capillary action is a particular problem for T1-11 since it is installed vertically with the bottom edge inches from the ground or actually in contact with the ground. The end grain is often overlooked in the painting process and is left untreated causing high moisture levels in the wood which inevitably leads to swelling, wood rot, and mold.

Problem #3 Unrealistic Maintenance Expectations

Without the building wrap and siding to protect it T1-11 relies heavily on homeowners to keep it painted every 3-5 years otherwise you risk major failure of your siding. If you forget to paint wood siding often enough it gets exposed to the elements and turns grey which can be sanded and repainted.

T1-11 is different because it is being held together with glues and binders that don’t perform well when exposed to the elements over time. The siding begins to delaminate or swell and structural failure is not far off when it’s left bare or goes too long between paint jobs.

Think of it like buying a car that needs an oil change every 300 miles instead of every 3,000 miles. Chances are you won’t keep up with that burdensome schedule of oil changes due to the business of life and your car won’t last.

Real Wood Siding

If you’re going to go with a wood siding, which I would strongly recommend, then stay away from T1-11 siding and choose a solid wood material that is made from rot resistant wood. You have a product that requires far less maintenance and can literally last hundreds of years with a little maintenance.

There is no such thing as a zero maintenance product and T1-11 is probably the furthest thing from low maintenance that you can find. Steer clear and you’ll avoid the trap that Benjamin’s Franklin spoke of centuries ago. “The sweet taste of low price is forgotten long after the bitterness of poor quality remains.”

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17 thoughts on “Why T1-11 Siding Sucks

  1. My mother built her house in Kodiak, Alaska back in the early 1980s. T1-11 was used down to the crawl space level. Kodiak is known for it’s stormy, wet weather. Never had a problem with the T1-11. In the 20 yrs she lived there, it was painted twice-in the beginning when built and the about 15 yrs later. It was sold after she passed and the new owners have repainted. that was in 2001. No problems with it.

  2. I have T1-11 siding on my house.. it’s been there for 40 years.
    Now I know that ‘things’ were made better in the day and just recently discovered some rotting wood.
    I’m replacing some of the siding with T1-11
    again and will use a good paint to protect the wood.
    Michigan woman

    1. Me, too. Mine has been on my house 44 years, in Michigan as well, and is still in great shape. It is not in contact with the ground. My neighbor replaced a sheet on his house, once, but his has held up, too.

  3. T1-11 is fine. Just paint it and keep it covered. Like all things exposed to the elements, it needs protection.
    Unlike redwood and cedar (rot resistant-not proof), T-1-11 is literally $30k-50k cheaper for the average ranch home of 1500 sq ft. and you’ll need to treat those ship lap options too with painting or staining.

  4. My shed is 17 years old and looks great! Painted it twice no problem at all. Use a good paint and it will be fine

  5. I have a 120sf backyard shed that was built a couple years ago with T1-11 siding. It’s 16+” off the ground (skirted crawl underneath, no ground contact)and is painted with a good quality house paint. I’m kind of stuck with it for the foreseeable future. Is there anything else I should consider doing to preserve it as long as possible?

    1. NO. YOU’re all good. Keep it painted in good condition. You’re all set. If you insulate you’re shed on the inside, it’ll be even better.

  6. Hi Scott,
    I look forward to your weekly newsletters with valuable comments, hints & tips.
    My sideline work in Sydney Australia is being a Handyman all rounder.
    It’s not the quoted price for a job, it’s the finished quality that my clients appreciate.
    I quite often go the extra mile and time for free. Word of mouth has paid off.
    Keep up the informative newsletters. No one knows everything, i’m still learning.
    Thank you.
    Kind regards
    Howard Armstrong

    1. Howard,
      Thank you for sharing your story. It sounds like you put great care into your work.
      And it’s nice to hear that word of mouth is still going strong in this industry!
      Kind regards,
      The Craftsman Blog Team

  7. I have an old house with a post on beam foundation. While it has good clapboard siding above, from the floor down to the dirt the siding is plywood covered in some sort of thin fiber cement board. I needed to replace one section of this siding. The plywood that is in contact with the dirt is rotting. What would you replace this with?

    1. Replace it with treated plywood if its ground contact.
      Cement board works great if you can stand the rough finish.

      Finish with primer&paint or stain on wood. P&P on cement board.

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