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Diagonal rainscreen

James Kelly | Posted in General Questions on

Hello Again,

I have framed my house in climate zone 6 and now planing for my exterior insulation/ rain screen/ and cladding choices.  So far this is my assembly from inside out.

5/8 Drywall
2×6 wood studs 16″ oc
Stud cavity insulated with damp spray cellulose
1/2″ osb sheathing w/ taped seams
Tyvek house wrap
The windows are installed as outie windows and their bucks sit 2 3/4″ proud of the sheathing

I have also purchased enough 2″ Rockwool Comfortboard 80 to cover the exterior.

My original plan was to put vertical 1×4  furring over the rockwool to create my rainscreen and side with LP Smartside Lap Siding.  

(** Side note – I posted another question about this assembly back in December and Michael Maines alluded to the fact that lp required 2×4 furring over mineral wool.  I thought I found a work around by using 3/4″ southern yellow pine as stated in LP’s technical note 18.  However, after more research recently, that is only acceptable over “rigid foam insulation” and does not allow 1×4 over mineral wool insulation.  Thanks Michael, I should have listened to you sooner.)

Now my beautiful bride wants the look of board and batten for our house.  I have read as much as I can about rainscreens (mostly on this site).   So I looked into horizontal rainscreens.  There have been some comments asking about running the rainscreen diagonally to allow for vertical siding while still having the benifits of vertical rainscreen.   So here are my questions and remember i must achieve 2 3/4″ thickness for insulation and rainscreen for my windows and doors.

1.  Does anyone have any good information on running a rainscreen diagonally?

2.  If running the rainscreen horizontally is there a fastening schedule for going over 2″ of mineral wool? (all fastening schedules I have found for rainscreens over insulation have them running vertically)

3.  Is there any way to detail this in which lp would approve of or do I need to find another cladding?

4.  Is there any product other than wood that is 3/4″ thick that I could use?

Thank you in advance for your help,
Jim

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Replies

  1. Expert Member
    Akos | | #1

    You have pretty much designed yourself into a corner.

    If you are using their 16" wide siding, with the 16oc spacing, you can just go with vertical 2x4 on flat and extend your window trim a bit to make up for the gap.

    Hardie siding can be installed over 3/8 or 3/4 strapping but depends on the style and wind load. You'll have to check the design manual for the style you want.

    I've done budget semi metal board and batten by getting galvanized sheets sheared to width, nail up, paint in situ, finish with cement board battens. There will be some oil canning, so it all depends on how picky one is.

  2. GBA Editor
    Brian Pontolilo | | #2

    Hi James,

    I have seen builders install furring strips lattice-style to create a rainscreen for vertical siding. The first strips go on vertically and a second horizontal layer is installed on top of the vertical furring strips. This way, the horizontal furring doesn't inhibit drainage. I'd have a professional advise you on that to make sure that you are using sufficient fasteners, an acceptable fastening schedule, etc. Unless there is something I'm not understanding about your assembly, if you were to install horizontal or diagonal furring, the only possible fastening schedule would be to hit every stud.

  3. James Kelly | | #3

    Thanks Akos and Brian,

    Yes, I have pretty much designed myself into a corner.

    To clarify on the fastening schedule question this is more of what I'm looking for either for horizontal or diagonal.

    1. Spacing of strips
    2. Size of fastener
    3. With a 1x4 running horizontal or diagonal there would be enough space for 2 screws per stud. Overkill? But would create somewhat of a truss effect.

    Thanks again,
    Jim

    1. Expert Member
      Malcolm Taylor | | #5

      Jim,

      Why not use Hardi panels and trim for board & batten? that way you can use vertical strapping.

  4. GBA Editor
    Brian Pontolilo | | #4

    Hi James,

    This is not something I would advise you on. As I said in my first response, I think you should consult an engineer. You can also look at the IRC (you can read it here for free: https://codes.iccsafe.org/category/I-Codes). I believe there is a fastening schedule for furring strips, at least for wood siding. For manufactured siding, I think it says that you should follow manufacturers' specs.

  5. Expert Member
    Akos | | #6

    You won't find board and batten installs over horizontal/diagonal screens because it is not a stable substrate. This is similar why they don't allow runs across multiple stories.

    If you want to install LP B&B, then you need:
    -engineer to spec horizontal strapping size and fastening schedule
    -engineer to spec fastener schedule for attaching the 2x on flat vertical strapping
    -install siding per manufacturers spec on this "approved substrate"

    I think the simplest is to go with a siding that can be installed over 16" oc vertical strapping and call it a day.

    More expensive, but many standing seam metal panels can be installed over horizontal strapping.

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