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Open rainscreen subsurface

snmhanson | Posted in General Questions on

I am working on two 10’x10′ open Ipe rain screens.  The Ipe will run horizontally with 1/2″ gaps.  The area that I am installing was prepped for a stucco finish that was never completed but does have the scratch coat applied.  I am trying to figure out the best way to move forward with the rain screens.

I was initially thinking of installing a self-adhering wrap such as Delta Fasade or Invisiwrap over the scratch boat but I’m not sure it would stick – and I’m having problems finding it.  Additionally, when I talked to a rep he said he thinks a rain screen specific wrap would be overkill since the wall should already be water proof.  So now I am thinking a paint on membrane or maybe even just a UV stable paint should do the trick.  I wouldn’t mind some sort of a membrane over regular paint just as an additional layer of water resistance.  In any case, does anyone know of a commonly available product that would work for this application?  I live in a small town and the supply stores don’t have any rain screen specific products.  There is a Home Depot about 30 minutes away, or my local stores would have basic paints and such.  Also, any advice on what would work for battens assuming I can’t find rain screen specific products there either?  Since it is an open rain screen I need everything to be black and UV stable.

Thanks for any advice,

Matt

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Replies

  1. Expert Member
    Malcolm Taylor | | #1

    snmhanson,

    I would use an elastomeric stucco paint applied after the battens were installed.
    This one is available at HD: https://www.homedepot.com/p/BEHR-Premium-5-gal-Elastomeric-Masonry-Stucco-and-Brick-Exterior-Paint-06805/100158685?modalType=drawer

  2. Expert Member
    Akos | | #2

    For battens, I usually paint pressure treated wood black.

    You can also rip some of the dark composite deck boards and use it as strapping if you are looking for something more durable.

  3. snmhanson | | #3

    Thanks for the replies. I am off to Home Depot to grab some of the Behr Stucco paint linked above. I'll also try to find a material that will work for the battens - maybe a piece of synthetic decking to rip down as suggested, though I'd rather not have to do any major cutting if possible.

    One additional question - what is the thinnest I could reasonably go with for the battens? One area that I'm doing has a couple of windows that are only about 1/4" proud of the substrate material so I'd like to go with as thin of rainscreen as possible for that area to not have the windows sunk back too far behind the Ipe face. This area is well protected and would very rarely be exposed to rain or sun. I will flash the top of the windows to control any moisture that does happen to find it's way there. I would love to just do 1/8" battens in that area if possible.

    Thanks,

    Matt

    1. Expert Member
      Malcolm Taylor | | #4

      Matt,

      With an open-cladding and a smooth substrate, I don't see why 1/8" battens wouldn't work. The downside is that with thicker battens you could rely on just fastening the Ipe to the battens. With only 1/8" to bite into, the fasteners are going to have to penetrate through the stucco into the sheathing behind. If it were me I'd build out the window frames and use something like 3/4" for battens.

    2. Deleted | | #5

      Deleted

  4. snmhanson | | #6

    Thanks for the advice on the batten thickness. I ended up finding some plastic trim pieces that should work well for the battens. I got 1/4" thick for the wall without the windows and 1/8" for the wall with the windows. In both cases I'll pre-drill and just screw through the stucco and into the plywood sheathing under that. I'll try to hit a stud if it works out (which it should at least on the ends), otherwise hopefully the sheathing will have enough holding power. Of course, this brings up a couple other questions.

    First, with the Ipe will two screws on each of the ends and two in the middle be enough or should I add one or two additional attachment points? Ideally I'd like the least amount of screws showing as possible.

    Second, is it recommended to run the batten all the way up and down or can I just cut the battens into ~5" long strips and then put a strip behind each board where I am screwing it in? Doing that would help hide the batten and also require a bit less material. The plastic I got is white in color and I will paint it black, but I still wouldn't mind keeping it out of sight.

    Thanks again for all of the help.

    Matt

    1. Expert Member
      Malcolm Taylor | | #7

      Matt,

      Open cladding shouldn't be considered a rain-screen, and needs more careful detailing of the layers underneath the siding.

      The vulnerable points when the wall is all finished will be the screw holes through the stucco. That's why I suggested fastening the battens before coating both the stucco and battens with the elastomeric paint. Small strips of plastic behind each board will have moisture running down the wall behind them. Depending on your climate that might not be the big of an issue. Here in the PNW I could almost guarantee water intrusion into the wall with that detail.

      Have you considered using trim-head screws for the cladding?

  5. snmhanson | | #8

    Thanks for the help on this Malcolm. Yes, I am planning on using trim head screws. However, I may need to rethink things a bit based on your last post. We live in the PNW as well - the Columbia Gorge more specifically. One of the walls is exposed to very consistent high winds and sometimes rain along with the wind. Construction wise, the builder put a good house wrap on before the stucco guy came and did his work up to the scratch coat before bailing. So that's where we are now.

    I have no problem installing the battens before painting, however, I was unable to get the elastometric paint in a dark color so I ended up just buying regular brick and mortar paint in black. I suppose I could go buy some of the elastometric paint and do a couple layers of that and then the regular black paint over that if it would make a difference. I'm not worried about water getting through the wall as it stands now, but if the screws will allow water through I need to deal with that.

    I've attached a picture to better illustrate what I'm dealing with. Seemed simply enough when I started this, but like everything it's getting more complicated as I go.

    Any additional advice would be great.

    Thanks!

    Matt

    1. Expert Member
      Malcolm Taylor | | #9

      Matt,

      It depends on how finicky you are willing to be. The small strips would work as long as there was a way to stop intrusion at the top. Something like a a dap of caulking to bed the top of each strip in could be fine. Hiding the strips makes sense if they are plastic. it would be really annoying to try and re-cover them if the black paint started to come off once everything was installed.

      I missed your question about spacing of the supports. Typically you wouldn't want to go further that 2 ft oc, but with Ipe you might stretch that to one at each end and two intermediate ones. Going a full 5 ft might turn out pretty wavy, and with only a 1/8" cavity risks closing it off in spots.

      Form the photo I think the open cladding will look great there.

  6. snmhanson | | #10

    I'm back with another question. I've got the battens ready to go and will be able to install the wood soon. The battens are plastic mouldings that I painted black and then wrapped with black UV stable tape. I also applied weather stripping to the backs of them which will hopefully create a water tight seal between them and the house once fastened down.

    I have been locating the studs as I was placing each batten over a stud and then using 3" screws through the Ipe, batten and sheathing and fasten 1"+ into a stud. As it turns out, the studs are not at ideal locations. There are no studs that I can hit at the ends of the boards and the nearest stud to each end is about 16" in. Since there are no studs at the ends all of the connecting points will be pushed in more towards the middle and they will be off-center/non-symmetrical as well. I can deal with the off center issue, but I do think it is probably important to have connecting points within 6" or so of the ends of the boards. So, my only easy solution is to rely on the plywood sheathing to fasten the Ipe to. Will this be strong enough or do I risk the screws ripping out of the sheathing if the boards flax or warp? Or even worse, the Ipe boards flexing and pulling the sheathing off the studs in places. If the sheathing is strong enough that will solve all of my problems. If not I'm going to have to take a step back and think about an alternate way of doing this.

    Thanks for any input!

    Matt

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