Fiber Cement Board Installation Help

I am currently in the process of designing a new modern home in the St. Louis market for myself. For the exterior cladding, I am looking into using 4' x 8' fiber cement panels along with brick. The look that I am going for is obviously the panel look where the panels are butt jointed. I have looked at the installation methods proposed on James Hardie's website and they suggested attaching the panels to the 2' x 4' structure (on top of the sheathing and wrap) and then caulking the joints. Being a developer and knowing the what it means to have caulk as your first line of defense against moisture infiltration, I am concerned that this method is vulnerable to leaking.

Has anyone had any experience in installing fiber cement panels using this technique? Any other suggestions on how to install these panels and get the panelized look? What about moisture penetration where the fiber cement board is fastened? Thanks in advance for any insight.

You need to flash each joint. This gives you the metal exposed at each joint but that can look good as well. Look at some of the close up photos of the Glide House as this kind of cladding is used on portions of it.

Thanks for the information. I checked out the detail on their website. I assume that you only need to flash the horizontal joints and can just caulk the vertical joints. The horizontal flashing should also allow water that leaks through the fasteners to weep out as well.

When I was looking at this kind of system I did find several materials that can be put between the concrete panels (or stucco) and the waterproof layer. It is a pressed-flat tangle of polymer strings that provides multiple pathways for any moisture that gets past the concrete or joints to pass downward to an exit point. I seem to have misplaced some of my bookmarks for this stuff but I will keep digging.

here is one: http://www.dryvit.com/specs.asp?country_id=1

I always thought the rainscreen concept was how most all these fiberboard panel installs were done... as I plan on doing the same.

Rainscreen (as far as I've been able to understand) is merely providing a gap between the exterior sheathing with either the old method of furring strips or newer products. The strips are fastened through some wrap to the structural sheathing. THe furring is vertical and the panels are fastened to them. All panels require some gap for expansion/contraction, but HOW the seams are sealed is always the question.

Flashing seems obvious, but I've never been found of that flashing all over the place... especially JUST horizontal. I HAVE seen many a house clad with CFB, BUT NOT use flashing at the seems. No where has this been explained to me. Maybe some of you architects can share your thoughts?

The gap is for breathing/ventilation so the sheathing does not rot (if it was traditional wood). I guess this is region-dependent. Seeing as how I'm in MI with climate extremes I chose to go this route - ventilation. Any moisture/rain would have air space to evaporate or trickle down to ground in the gap and no rot. Because my house will be SIP, I figure reducing the chances of rotting the SIP sheathing (OSB) is important, too.

Here is my thoughts on LACK of flashing. Please clue me in on how stupid I may be:

If I leave a gap (up to ~1/4 depending on my cedar or CFB siding) the rain or snow could get into the gap space, but then the gap of 1 (furring strip thickness) should be enough to let moisture trickle down or evaporate up. THe rainscreen is decorative and protective (but protective to a certain degree). Even my cedar siding (horizontal) will have gaps in between planks as I'd rather not get the TG stuff.

SHouldn't the building wrap (tar paper or etc.) be enough protection for the SIP sheathing against moisture?

My biggest concern is bugs. I figure NO method is ever tight enough to prevent bugs from getting inside the gap IF they want to get in, so why bother? COuld I treat the gap space with insecticide or something? I know the top and bottom of gap can have those products that allow moisture/air travel, but block bugs of a certain size.

They never mention insects when they talk of the benefits of a rainscreen. I have t and g cedar on my house now and the carpenter bees love it. I shutter to think at what they would do if they could get in behind a rainscreen.

uncleho - I would look into getting your property treated anually by Orkin or one of those companies if you are worried about it.

Eegs,

Thanks. I just wished most mags would get into the DETAILS of construction instead of the esthetic generalities, because I always see these rainscreen facades of cedar or CFB or whatever and they look like any insect could build a Condo in them.

I got kids and wonder how sensible Orkin'ing the entire house every year would add to their health risks.

What do you do about the bees? Insecticide?

[quote:uncleho format=text/plain]Eegs,

Thanks. I just wished most mags would get into the DETAILS of construction instead of the esthetic generalities, because I always see these rainscreen facades of cedar or CFB or whatever and they look like any insect could build a Condo in them.

I got kids and wonder how sensible Orkin'ing the entire house every year would add to their health risks.

What do you do about the bees? Insecticide?

[/quote]


Yeah, I get it sprayed. I hear you on the risks. I didn't really have any other options at the time though. I am in a high alert area, so they claim as far as pests go. My lot is heavily wooded and there are tons of carpenter bees and ants in my neighborhood.

My plan is to take out some of the damaged trees and get rid of all the wood on my house. I'd like to replace the cedar with hardi and replace all the soffits and fascia with vinyl:disgust: or something and coil. When I get that finished I'll stop with the pest treatments and see how it goes.

Hardi makes soffit panel as well - you may like it better than the vinyl.

i had heard that before, but had never seen it. i'll check out the website.
thanks greg.

Since we're on the cement board subject:

I'm having a hard time sourcing Z channel for flashing because I'm not sure who would typically supply it. I want something with a longer exterior face, say maybe 1.5-2.
What kind of supplier or who can I go to and get just X number of lf of this? Or does it need to be custom bent? By whom?

A reasonably well-equipped sheet metal fabricator (one who does duct work, for example) should be able to custom fabricate Z flashing from flat strip.

One thing I've never satisfactorily resolved with the combination of fiber cement panels and flashing is what metal to use. Both zinc (as in galvanized steel) and aluminum have reactivity issues when in close contact with Portland cement-containing materials. Stainless steel would be fine, but it's quite a bit more expensive than the others.

-Steve

If you're not remodeling why not have the real thing. Concrete walls. I've always loved the look but couldn't come up with a good way to easily include insuslation. The other day someone sent me some info on T-mass. It's used mostly in tild up warehouses but seems to be catching on for residential. Concrete walls, Insulation, no bugs! and LOTS of thermal mass that according to newer research cuts utility bills. See what you think.
http://www.dow.com/styrofoam/na/news/t_mass.htm
http://www.thermomass.com/
http://www.dow.com/styrofoam/na/pouredinplace/index.htm
http://sitecast.ca/content/tilt_up_construction/tilt_up_energy.php
http://www.long-visio.com/
Good Luck!

Previously Splatgirl wrote:

Since we're on the cement board subject:

I'm having a hard time sourcing Z channel for flashing because I'm not sure who would typically supply it. I want something with a longer exterior face, say maybe 1.5-2.
What kind of supplier or who can I go to and get just X number of lf of this? Or does it need to be custom bent? By whom?

Take a look at www.fibercementproducts.com they offer the highest quality of fiber cement products and substrate systems at the best prices on the market.

Cheers,

Jeff

you dont need any flashing. use rainscreen concept with open joints. looks great, makes healthy facades. apply layer of vaproshield, and attach hardie (or other panels) over vertical strips. i am doing same on my house. absolutelly recommend this system over flashing at each joint.