rainscreen siding

I'm in dire straits. I live in West Seattle in a 1940 home that i purchased 1.5 years ago. I have been having some health problem in the form of an allergic skin condition that i have come to find out is the result of living in a home that has mold. Not toxic black mold but a mold non the less. We aren't sure the exact cause of the mold but one theory is poor roof ventilation. The house has no eves and the thought is that condensation over the years has taken its toll.

How this all came about....i had our home tested and they found high levels of mold in the walls. So i removed the sheet rock on the interior walls to find that the exteroir sheathing on the house was a product calle GYLAP, an exterior sheetrock, which seemed really stupid. It was covered in mold. So then I started to rip off the vinyl siding that was placed over top of the originial cedar lap siding when the house was insulated with that blown newspaper material cybox or something.

So I ripped off the GYLAP to find I need to replace part of the header plate, top plate, corner post and most of the studs.

This all lead to the decision that if we are going to redo the entire exterior of the house and alot of structural framing we should design the second story addtion that would give us the water view.

SO NOW TO MY QUESTIONS I'm trying to design my own house, working drawings and all since we can't afford an architect. I know it sounds crazy

I'm trying to find detailed drawings on how you fur out the windows with a rainscreen application.

Also can you use hardiplank in a rainscreen instead of cedar like i usually see on homes

hardiplank isn't stiff and is that a problem????

i want it to look like this guys siding http://www.blipdesign.com/images/phinney_detail_big.jpg

i have also read of problems with bees nesting in the air cavity and how do you prevent that?

any help in the form of detail drawing that someone could provide would be great and also methods or directions on how to apply this. would be most appreciated.

I have my own graphic and web design company and would be happy to trade services for any one in the seattle area willing to work with me. I have my own web hosting company and can give free hosting in exchange for help.

We are having to pay for all this out of pocket since insurance isn't going to help so any help would be great

David Billinghurst
daveb@puredesigngroup.com
http://www.puredesigngroup.com

Dave,
A few years back the City of Seattle performed an in-depth study of moisture damage in newly constructed buildings, and their results also include recommendations for new construction methods. Here's the link, and I believe you can download the study as a PDF from this page:
http://www.cityofseattle.net/dclu/news/20020926a.asp

I would also suggest you comb through the writings of Joe Lstiburek and others at the BSC page:
http://www.buildingscience.com/resources/resources.htm

His book Builder's Guide to Mixed Climates is worth checking out from that fancy new library you guys have there. I think you'll be able to find good rainscreen/window details among these sources.

I hesitate to make a recommendation just yet on the use of hardiplank in a similar application to your nice photo... but if you go that route then by all means be sure to prime and paint it on all sides. I would guess that you could address the waviness of the siding by placing your furring at 12 on center rather than 16.

Cheers,
JB

Hi David,

darn northwest rain. i'm in portland. it is always a detail challenge. couple of thoughts to get you rolling:

-typically the rainscreen detail is used with wood siding for the purpose of allowing the wood to dry out evenly and completly from the front face and the back of the siding(where the airspace is between the siding and the housewrap on sheathing). It has been said that this is not neccesary for hardi siding because it doesn't soak up moisture like wood.
-if you go with the the rainscreen, the furring strips can be as little as 1/2 wood. with the siding on the furring strips, depending on the type of windows, the siding might just butt up to the window frame. or you can put a thin trim board around the window to allow the siding to butt in to.
-an important detail to pay attention to is flashing the openings. this is where alot of the moisture can enter the wall cavity. take a look at window websites for flashing details (such as www.milgard.com) or window wrap manufacturer such as Vycor by Grace Building Products. Also Tyvek house wrap.

m.o.d.

Wow, that came out all wrong! Thanks for the correction Mark.

so it looks like from the link that eamesdaedelus sent me that you dont have to apply the hardiplank like th e cedar application in my example with the screws and horz spacers. you can apply it as it as norrmal lap siding looks but on the furring strips. i guess the seams have to line up on the furring strips to attach and then caulk?

that PDF was very informative.

but still good to back prime any product cedar or hardi. with an oil based primer. som e of the article mentioned maybe some latex brands that might work. any suggestions??

how do you mount metal cladding onto the rainscreen. i saw a house close by that is underconstruction and it had the a sheet of cdx on the furring strips and then the metal attached to that? why would they do that. wouldn't you just screw to the furring strips? or does it allow you to use more screws to attach to the plywood that are needed???

do you mount the hardi panel (like you see with the corner bolts) the same way on the furring strips??

The building science site had great sample drawings.

but i couldn't find any good flashing details


thanks to both you guys for your info. great stuff.

would would be recommended for building paper? i have read to use 30lb felt?

that GRACE stuff looks good for the flashing. do you need to use metal flashing anywhere on the window top or bottom trim?

sorry so many questions

Dave,
Sorry if I sound pessimistic, but I'm feeling doubtful that you'll get the same detail to work with hardie siding. It seems like the things attracting you to the Blip Design project are the spaced siding (1/2 or so gap between each plank) and also the exposed fasteners. Am I right on this??

Hardie really likes to be nailed and then painted, making the fasteners disappear. I don't think you'd want to screw it on with exposed fasteners, but maybe I'm wrong on this. Also, I'd be surprised if they'd honor the warranty if it was not installed in a traditional lapped siding method... I would go talk to a dealer about this before you get too far into it.

You might also check this [url href=http://www.livemodern.com/forums/dwell/materialsmethods/465562408495?b_start:int=0#758165267318]thread[/url] for more discussion of fiber-cement (aka Hardie)installation in a rainscreen.

Cheers,
JB

you are right jb, i think if i was to use the hardiplank i would apply it in the traditional lapped method but on the furring strips. i didn't realize you could apply it in the rainscreen method like that. the link i got from another post showed me that.

would you caulk just the seams where they meet that you would have to line up on the furring strips?

i did read a thread on this site about someone who mounted hardipanel that he cut into 4x4 squares with bolts. that is where i got the idea. i figured it was easier to use planks then panel i would have to cut.

i think i will try and use some cedar in the spaced fashion on a part of the house along with some metal here and there to give it the look i want

Plus you would probably have to drill the cement board first before you could use the exposed fasterners. and that would take along time

its hard to find out about these modern cooler applications. It seems alot of architects and builders don't have an experience in this type of stuff. So this forum is a really great tool.

Thanks everyone

Dave,
I know you were looking for some flashing details... here's some that are easy to understand:

http://www.apawood.org/bbh_index.cfm

These are not rainscreen specific, but should be helpful nonetheless.

To answer one of your other questions, I would probably caulk at the vertical joints, but if the hardie plank is really installed in a rainscreen method, it is not necessary to caulk all of the horizontal joints.

Cheers,
JB

Thanks for all the info. Great stuff.

I am considering installing HardiPanel on my new house with this rainscreen method in an effort to acheive that modern look of Given that I live in the Pacific Northwest (rain, rain, rain!), I think that the rainscreen makes perfect sense. However, does anyone have an opinion on whether a housewrap such as Tyvek is adequate to protect the house underneath the furring strips, or has anyone considered using a waterproof product such at the Grace Ice Water Shield (typically used as a roof underlayment?)instead of your typical housewrap?

I recently came across this site, http://www.modern-shed.com , that sells prefabricated buildings. They have that gridded look with space gaps and exposed fasteners that I want to replicate. In chatting with the company, they use hardipanel with a rainscreen method over the Grace Water Ice Shield. I asked them about issues of the builidng breathing, but they felt that since the structure was so small, and does not have an interior source that creates moisture, it was not that big a problem for them.

For my own home, I am concerned about trapping moisture in the walls if the house is waterproofed. Would installing a whole house heat exchanger balance this problem out by (ideally) removing moisture from the inside of the house continously?

Thanks!

Sara

Sara,
I can't address your specific situation, but I would do a thorough amount of research before putting IW Shield on your entire building in lieu of a typical tyvek or felt paper building wrap.

If you are really doing a rainscreen, then the airspace alone will provide enormous protection against inward vapor drive, and also provides a nice drainage plane which should eliminate the need for IW Shield. Even in our wet climate, you won't get prolonged wetness in the wall with a true rainscreen. Taking the absorbent siding out of contact with the weather barrier gets you pretty far.

Personally, I think you'll get more mileage in the thermal moisture protection department if you spent that money on an exterior insulation approach instead, but that's another discussion in itself.

I can possibly email you some good literature on this... P.M. me if you want it.
Also, check the links earlier in this thread for some more good info.

Cheers,
JB

Neither the tyvek or the Grace product are made for continuous exposure to UV, and even though very little light comes through the gaps in the rain screen you will be inviting trouble down the line. The tyvek will allow water vapor to pass, but the ice shield will not. You need a vapor permeable water proof barrier that also withstands UV. You want to use something like [url href=http://www.henry-bes.com/airbarriers_perm.asp]Henry Air Bloc 33[/url] which goes on as a liquid. I think you can spray or roll it.

How about the tradional 15 or 30# Tar Paper OVER the typical building wraps of today?

My SIP house will come wrapped with Greenguard (Pactiv) Ultra and I was just going to fasten Tar Paper over that. I would see black between the seams of the rainscreen and... I don't know about tar paper's UV resistance???

this is the same issue I am running into — UV rating for 30lb felt.

UV rating for 30lb felt = BAD. That's why it's always covered by roofing. As I mentioned in another post about rainscreens, if you are going to do it, you really need to look into VaproShield's products. They are designed for rainscreen applications.

www.vaproshield.com

    -R.