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Battens for both strapping foam and nailing siding

brooksbend | Posted in General Questions on

Hi, I’m retrofiting an old timber frame barn to be insulated with radiant concrete slab, using techniques outlined on this website.

I’m detailing the siding now, and I’d like to keep the New England barn look and have rough cut vertical pine boards as the siding. The current siding, reverse board and batten with 1/4″ battens and 1″ boards, will become the “sheathing” that two layers of 2.5″ foil-faced polyiso will be fastened to.

For fastening, my thinking is to use vertical rough-cut (actual) 1″x3″ timberlocked through the existing siding to 4″x4″ nailers that are fastened in between the posts of the barn on the interior. What I’d like to do is use those as the battens for the siding as well, 1″x10″. This means I would put the 1″x3″ strapping every 10″ on center, and then nail the 1″x10″ vertical boards to the strapping.

The trouble that I see with this detail is expansion and contraction of the battens and (especially, given the width) the boards. Ideally the battens are screwed down and the boards are screwed next to the battens into sheathing to allow for expansion and concraction of the two layers of wood. I can’t do that here because I am using those battens to fasten the siding.

Judging by all the barn siding I’ve seen in the area and the many screws/nails in boards and the fact that they are not cracked or warped, and given that I’m going for an exterior appearance of a classic barn in this area (Western Massachusetts) I’m not too concerned about it. But theoretically I am concerned, so wanted to see what y’all think. If I follow this detail will I have problems with cracked and warped boards down the road?

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  1. ohioandy | | #1

    Having done the timberlok-through-batten-through-thick-foam thing, the first thing that comes to mind with your plan is that you'll see every single giant screw head from a hundred yards away. The narrowness of a 1x3 forces you to place the screw in the center, which would be visible between the 1x10 boards. What about going with a wider batten to allow the big screws to be off-center (out of sight) and give you more bearing surface for the wide boards?

  2. brooksbend | | #2

    ohioandy, I should have clarified that I'll be butting the boards against each other. I guess the classic reverse board and batten has a gap between the board where you can see the batten behind. I am going for it to look like vertical boards against each other, the batten acting as weather protection, and in this case strapping for the rigid foam.

    I also forgot to include context that the reason I'm trying to double the function here is to avoid having the get shiplap siding, which would cost twice as much as the square edge boards. I may just have to do it the "standard" way and have a grid of vertical straping, horizontal nailers, and then shiplap boards.

  3. Expert Member
    Michael Maines | | #3

    That's more or less what we did on this outbuilding: I chose 6" boards partly to minimize movement (and partly because we wanted to use white cedar which tends to be narrow boards).

    A few years ago I remodeled a house built in the 1970s with 5/4x8 white pine reverse board and batten. I was impressed that it had held up very well. I wouldn't try 1x10 reverse board and batten but I would use 5/4x8 and might consider 5/4x10.

  4. brooksbend | | #4

    Michael, thanks for the reply. Can you help me understand how the extra 1/4" thickness helps in this case? And we're talking actual not nominal dimensions, correct? Are you still okay with 1" for the battens or would you bump those out to 5/4 as well (to consider both movement and strapping issues)? And 3" wide okay? If I bump to 4" then I'd have a ratio of 1/3 batten to 2/3 vent gap, which is why I like 3" wide battens instead, just afraid of them splitting. So maybe the 5/4x3 would take care of that concern.

    1. Expert Member
      Michael Maines | | #5

      The thicker the board, the less chance it will cup, just like the narrower the board, the less chance it will cup. The project I worked on had rough-sawn 5/4 but smooth-planed would work as well. 5/4 is usually about 1 1/4" when rough and 1 1/8" when smooth-planed, but it can be anywhere from 1" to 1 3/16" when smooth-planed. (aka S4S) Generally speaking, when using quotation marks, the lumber is the actual size stated, but without quotation marks it's the nominal size, before planing.

      Yes any thickness of batten should work.

  5. tjanson | | #6

    Double the cost for shiplap? Ouch. Sawmill I use in Northern VT is $0.25 / BF for custom planing, such as shiplap. 0.85 for rough cut 1x6 before planing. Well, those are the 2022 prices. I buy green hemlock shiplap 1x6. Maybe find a different mill?

    Oh, and I only use horizontal strapping (1/2" ply) with a beveled top edge to drain anything to the siding plane. Green shiplap siding will shrink enough to open up gaps on to allow for drainage, though it won't allow for the same level of ventilation that cross strapping provides. Not saying it's right, but I decided it was good enough for me.

    1. brooksbend | | #7

      We have a sawmill on the farm, my friend owns it. He does .90/BF for rough cut. Our friend who does it for a living (logs with horses as well) does 1.25/bf for anything over 12'. The place that will dress boards is doing 1.80/BF for 10" shiplap, planed on one side.

      Those are prices for good quality boards in our area. Happy to pay for good work, but want to be smart about it. Seems like I'll give the battens doubling as strapping a try, with .75"x3.5" battens and 1.25"x10" boards.

  6. user-6623302 | | #8

    Have you considered using SIPs? You can even attach drywall to the frame before the SIPS if you are using drywall or plaster. Simple and quick. Are you confident the frame is good? There is an old This Old House using this technique. Strip all the siding and start clean.

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