Housewrap/strapping with board and batten siding
Hello. I am thinking about using vertical pine board and batten on the exterior of my new house. This will require horizontal strapping which I initially thought should be placed over the house wrap. I then began to think about where the water will go when (not if) it finds it’s way behind the boards. Does the horizontal strapping impede on the water’s ability to drain down? Will it soak the strapping and eventually cause issues? Maybe I should place the house wrap over the strapping so that the water has a place to go, not interfering with the strapping? Any thoughts? Is there a house wrap/drainage surface that would work best in this application?
Thanks in advance. Matt.
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Matthew,
My own opinion is that you shouldn't worry. The small volume of water that gets past your siding will evaporate before it causes any problems.
If you are skeptical of my answer and still worried about this issue, most roofing supply houses sell notched battens that will allow for drainage when installed horizontally.
Fine Homebuilding's Project House shows a solution that's a bit time consuming but can solve this problem with cross-hatched strapping - apply your WRB, then vertical strapping, then horizontal strapping, then the vertical cladding. The linked image shows this pattern:
http://www.finehomebuilding.com/item/20808/sneak-peek-at-a-project-house-wall-section
Martin,
When you say "notched battens", do you mean notched strapping? My board and batten will be vertical.
While I have you, have you heard of mold or rot issues with the pine boards that have an air space behind them (this application)? I have been told that I need to prime the back side of the board for moisture protection. Really don't want to do all that labor if it's really not necessary.
One more thing. The wood I am getting will be green. When putting up the pine boards, what's your suggestion of how much of a gap I should leave? I was thinking 1/8". Batten will obviously cover expansion and contraction of the joint behind it.
Thanks.
Matthew,
I was thinking of your horizontal furring strips. But actually, a batten = a furring strip = strapping. These are just different words for what amounts to a 1x3 or 1x4.
Here is a photo -- not exactly what I had in mind, but it gives you an idea how these are used by roofers. I couldn't find a photo showing the exact type of batten I'm talking about.
.
Matthew,
I wouldn't worry about mold or rot. This type of assembly should dry readily to the exterior.
If you are installing green boards, you can butt them tightly to each other. They'll shrink. Fasten your battens with a single nail in the middle of the batten, aiming for the crack between the boards. That way your fasteners won't bind the boards (or cause splitting) as the boards shrink. If any of the battens curl, you can come back later with stainless-steel screws and correct the curling.
I understand that they will shrink, however, if I butt them up tightly together, they will never swell beyond that size? Thanks.
Matthew,
Trust me -- if you are putting them up green, they will shrink. They won't swell.
You could take a skill saw and make shallow cuts on the back of the strapping, for drainage if you are concerned. These could be whacked out in a short time, -eyeballing the distance in between.
Back priming is an upgrade choice as is rainscreening.
3/4" space will be nice critter condo. There are alternatives.
For the perpetually worried, installing the furring with 1/4" of slope per foot, in segments of 4-8 feet with a 1/4" gap between segments would guarantee pretty good drainage even while cleaning the siding with a pressure washer.
At 1/4"/foot there would be a 2" vertical offset at 8', an offset that can be restored in the next segment if you want all of your board & batten fasteners to line up in a level horizontal line. At 4' it's a 1" offset.
you can install a "drain wrap" under the strapping which has minute channels which will allow water to drain. I agree with Martin that it is unlikely that the strapping will rot, but this adds some insurance.
There are two main functions to rain screens: To provide a capillary break, and to vent the cavity to facilitate drying. While sloping the horizontal strapping or cutting drainage notches might deal with any intrusion of bulk water that gets past the siding, it doesn't allow any ventilation of the space. I guess it depends on your climate whether the drying to the exterior through the siding is sufficient.
AJ Builder, can u else orate on ways to keep out the bugs/critters from behind the 3/4" air space? I'm considering a similar application of b&b siding.
*elaborate
Rick, drain wrap leaves a less usable space for critters. Where I build back priming is enough, rain screening is not done most of the time depending..... much depends.... who what and desires... and cost.
Rick,
You might want to read this article: All About Rainscreens.