# Rainscreen behind T1-11 siding



## maddog1 (Aug 21, 2012)

Some contractors call it a rainscreen. I'm building a small barn (24 x 42) the exterior wall sheathing is OSB which will be finished with 3/8" T 1-11. Here is my question. 

1) I'm thinking of making a air gap or what some contractors call a rainscreen. This is a space between the OSB & the T 1-11 finish panel. Most use 3/4" PT strips to create the moisture drain path between the two panels. Is this absolutely necessary. 

2) If I go with the rainscreen, can I use something other than 3/4" PT fir strips. Can I maybe use several strips of 30 wt. felt paper stacked up to create a very slight drain-air gap. 

I'm here in SC & it can get really hot & humid in the summer & at times we have really heavy rains carried up here from the gulf. Thanks for your opinions.


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## lenaitch (Feb 10, 2014)

I don't think I have ever seen furring strips done in PT but I guess you could. Normally up here it is just 1x lumber. I would think building up layers of felt paper would be an unholy PITA and you might end up with an uneven surface. The goal is to create a space so the two panels are not right together so any water that does get through has a space to run down. Otherwise, it will get trapped in the sandwich and create rot. I would also wrap your osb in housewrap (Tyvek, etc.)


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## maddog1 (Aug 21, 2012)

lenaitch said:


> I don't think I have ever seen furring strips done in PT but I guess you could. Normally up here it is just 1x lumber. I would think building up layers of felt paper would be an unholy PITA and you might end up with an uneven surface. The goal is to create a space so the two panels are not right together so any water that does get through has a space to run down. Otherwise, it will get trapped in the sandwich and create rot. I would also wrap your osb in housewrap (Tyvek, etc.)


Thanks. I will have a house wrap in there as well. I forgot to mention. I've seen it done in your area with plain 1x. But then I came across some people using PT 1x3 or ripping PT plywood into strips. I assume they are trying to avoid rot out if there is a wet condition. I would rather use common 1x fir. And yes trying to do it with a felt paper build up would be a giant PITA> Hey Thanks for your opinion. Good advice.


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## joecaption (Nov 30, 2011)

Never got this new "rain screen thing".
I've worked on homes since i was 14, built at least 10 as well as garages and shed and never once done a "rain shield" never once a call back from rot.
Under durest I've done T-11 many times over OSB or plywood with nothing behind it and never had an issue.
I just despise T-11, there's just some many other ways to go with far less maintaince and chance of rot.


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## lenaitch (Feb 10, 2014)

joecaption said:


> I just despise T-11, there's just some many other ways to go with far less maintaince and chance of rot.


Interesting timing as I was just PM-ing with Pugsy about something I saw way early in his thread. I have to re-side a shed this summer - siding on stud, nothing fancy, so want something fairly thick - and plan to cost out panel (incl. T1-11) vs. shiplap options. The pre-finished shiplap are nice but too expensive. It is, after all, just a shed. Thoughts?


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## maddog1 (Aug 21, 2012)

lenaitch said:


> Interesting timing as I was just PM-ing with Pugsy about something I saw way early in his thread. I have to re-side a shed this summer - siding on stud, nothing fancy, so want something fairly thick - and plan to cost out panel (incl. T1-11) vs. shiplap options. The pre-finished shiplap are nice but too expensive. It is, after all, just a shed. Thoughts?


T 1-11 is less cost than shiplap or clapboard. Also comes in 3/8" & 5/8" thick. for a shed the 5/8" can go directly over studs with no other backing in most cases.


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## maddog1 (Aug 21, 2012)

joecaption said:


> Never got this new "rain screen thing".
> I've worked on homes since i was 14, built at least 10 as well as garages and shed and never once done a "rain shield" never once a call back from rot.
> Under durest I've done T-11 many times over OSB or plywood with nothing behind it and never had an issue.
> I just despise T-11, there's just some many other ways to go with far less maintaince and chance of rot.


Rainscreen is common practice in wet or heavy rain areas. Its done as a added precaution against trapping moisture between exterior walls like OSB & the finished wall. Also it aids a lot in helping to preserve pain finishes because it allows for moisture to leave the panel & air dry. And it prevents a lot of warp & rot issues at the bottom of the panels. Is in necessary to do. I think its a judgement call. In some areas it could be by code, but I don't know the answer to that.


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## Oso954 (Jun 23, 2012)

Various mfgs make plastic furring strips for rainscreen systems. Here is one example.
http://www.cor-a-vent.com/sturdi-strips.cfm
They allow you to use a thinner gap than most wood products.

If I was going 3/4, I'd just use 1x4 battens. PT is not necessary. If there is moisture entering the gap it drains immediately. 

Oregon is one state that mandates the system in new houses. They use 1/8 minimum gap.


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## Windows on Wash (Aug 30, 2011)

Most of your really necessitated rainscreen systems are going to be the Pacific NW and large commercial structures with huge weather facing exposures. 

Done properly, I don't see T1-11 leaking either like Joe said.


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