installing fiber cement siding over rigid foam sheathing

[dgbldr]

Re: installing fiber cement siding over rigid foam sheathing

Mark, how did you shoot those 16d nails through Hardie? Predrill and hand nail?

[Mark G]

Re: installing fiber cement siding over rigid foam sheathing

Hitachi framer with a Big Foot Flush Drive tip I got at a JLC Live.

[Ted S.]

Re: installing fiber cement siding over rigid foam sheathing

I think the Hardie instructions only allow for 1" foam like sailboat said, sounds like Mark's house is just fine however. Things are going to get interesting when IECC 2012 is adopted which requires exterior foam Zones 6 and up. These discussions will be quite common.

[jerrie]

Re: installing fiber cement siding over rigid foam sheathing

Hitachi framer with a Big Foot Flush Drive tip I got at a JLC Live.

Interesting insights on hardi over rigid foam sheathing. My dilema mirrors Mark G's situation the most. I have to redo aging (1983) vertical channel cedar siding (woodpeckers have become a real nuisance each spring). The cedar boards were attached onto horizontal strappings which were in turn screwed through the tar paper and the 2 inch rigid foam and into the 2X6 studs (16 oc) I believe they used a 4 inch deck screw of some kind to anchor it. There is no wood sheathing under the rigid foam just more insulation between the studs.Also between the strappings is a bit of bat pink. The home has been super energy efficient and rates up there with todays new builds, however, everyone who comes to look at the residing project either shys off or has a different idea. One hardi installer suggested I go right over my old siding which I didn't like that idea plus I've already got my new windows and don't think I could do that. Several have said strip everything down to the studs, apply wood sheathing and start all over again. That seems to be fixing a cart that's not broken (after all this is not about making my home more energy efficient). I even got a stucco guy in to take a look and he said wasn't sure if he could do even acrylic stucco just on top of the present rigid foam (might work but no warranty) Plus he was saying that the acrylic stucco woodpeckers kinda like (A+ for honesty). Sooo. I am thinking very carefully remove the siding and don't damage the underlying foam, repair any issues including the strapping....then I was thinking using a Hardie panel (cedermill) for a board and batton look. That way I can use the some of the existing strappings.The 4X8 panels would fit onto my existing 16 inch on centre studs. Again would likely have to use a very strong long screw to secure? I know it is not with Hardi's best practices but I don't have much choice. What do you think of that Mark G or anyone else?? PS I forgot to mention the studs are braced with 2X4s and metal diagnoal cross braces for added stability.

[Mark Parlee]

Re: installing fiber cement siding over rigid foam sheathing

Jerrie

Email me some pictures of your home.
You are getting ready to go down that long road of opinion and you might be swayed by one that doesn't work.

How are the old windows installed and how are the new ones to be installed. This detail could make or break the integrity of the entire job.

[Mark G]

Re: installing fiber cement siding over rigid foam sheathing

You'll get the best advice from Mark Parlee.

[ThingOfBeauty]

Re: installing fiber cement siding over rigid foam sheathing

Hardie can be attached to strapping. You have a lot of other things to figure out though.

[jerrie]

Re: installing fiber cement siding over rigid foam sheathing

I just wasted my morning waiting for a siding contractor to not show up (gee that irks me) Sorry no pics guys I don't think I can keep the old cedar on (and do a FC reside over wood siding). The old vertical cedar siding looks to be nailed into horizontal strapping (3/4"X 3.5" I believe). It looks like those strappings are every 16" (also into 16"oc studs). Sometimes the nailing pattern is something other that 16 but that could be that those nails go right into studs. The plan is to take off some of the old siding and see how the guts look. Also going to remove some around a window and see how that was done. The original builder and homeowner has offered to send me his old slides he took while the house went up. He apparently did some presentations on building with rigid foam sheathing etc. I should get those slides in the next couple days so I hope this will tell me a lot. My window guy really thinks I should gut the whole thing down to the studs and do wood sheathing and redo the rigid foam and VB. He is afraid of the weight of the FC into studs and strapping and the reliability of being able to hit those same anchors. I really hope we don't have to go to all that trouble. I was reading about FastenMaster HeadLok Screws for such applications. I was
thinking that a 5" one of these fasteners would work (thru siding 5/16", strapping 3/4", foam 2") into the 2X6 studs every 12". I will make more comments after I get those slides and remove some of the old boards. PS I'm thinking of 4X8 panels. Would you use the Hardie, MaxiTile or Certainteed??

[Mark Parlee]

Re: installing fiber cement siding over rigid foam sheathing

Jerrie
Without actually seeing the project all we can go on is your description.
Without this being what we would consider a conventional installation there are a lot of details that are tough to give advice on. I do agree with removing some of the existing assembly to view what is underneath. I really tend to go with your siding guys thoughts. If he is good at what he does and has experience you ought to put some faith in what he has to say. He is there and looking at the job, we are not. That is why I wanted to see some pictures, to familiarize myself with what you are dealing with.
If you are going to remove some of the siding take plenty of pictures and send them along.
Best way to do this is an elevation shot then close up of the area then a close up of the details. I do a lot of email and online consulting of moisture intrusion, construction defects and reconstructive remediation. This is the format I use with these projects. This takes some time and dedication to the process by both you and me, and I offered to help you out if you want to go this route.
It is really tough to give you any advice as how you should go about the process until we really know what you are dealing with. Once you get the slides have them all printed to digital images and send them along with the pictures of the home and the areas you tear apart. You can email them directly to me and I will direct you where to take more detailed photos.

I would not use Hardie, Maxtile, or CertainTeed on this project based on what you have explained so far.

[jerrie]

Re: installing fiber cement siding over rigid foam sheathing

I will get those slides digitized asap. That sample area of siding won't get pulled off until the last week of March so I may send them along before then. Thanks for your time and patience. I'm an amateur trying to get it done right. Yes I do trust my window guy and ultimately I know he won't do anything he doesn't feel is right. You wouldn't use any of the cement fibreboards?? Or you would but only if it had the wood sheathing?

[Mark Parlee]

Re: installing fiber cement siding over rigid foam sheathing

Jerrie

After I have the photos I will go into all of the details.

[Albion]

Re: installing fiber cement siding over rigid foam sheathing

I have completed several projects that use foil-faced polyiso as the exterior rigid insulation board. I install 1x furring strips vertically over the foam to support fiber cement lap siding. The furring strips are attached to the studs with 4" screws at 6" to 8" o.c. I do not use the foam as the drainage plane however. The foam is installed over a continuous rubber membrane which is installed over a 1/2" CDX plywood sheathing.

As mentioned the air space increases the r-value slightly, the foil facing gives me a radiant barrier (a benefit here in Austin) and a ventilated siding will maintain it's finish over time better than an unventilated siding.

Good luck with the project.

Howdy, am interested in using Tyvek® DrainWrap™ over OSB then foam & a rain screen with cement lap siding. Can you elaborate more about what & why the rubber membrane in your projects?

[Lavrans]

Re: installing fiber cement siding over rigid foam sheathing

Howdy, am interested in using Tyvek® DrainWrap™ over OSB then foam & a rain screen with cement lap siding. Can you elaborate more about what & why the rubber membrane in your projects?

Double that- I am curious about the what & why also.

[parrotcam]

Re: installing fiber cement siding over rigid foam sheathing

Hi,

I did a modest remodel that took on a life of its own on my Oregon bungalow. I eventually replaced over 60% of the house.

It is all done with sealed and taped 1" T & G XPS over 15 lb felt. That was followed with 1 1/2" X 1/2" PT ply vertical strapping with screened vents top and bottom and finally sheathed with Hardie plank. I used screws with cutting tips and ribbed heads to apply the siding.

I found two screw versions that both worked well but one had a proprietary head socket that firmly gripped the matching driver. The other was standard torx drive. I ended up with a (rather laborious) procedure that involved driving the screw until the head seated flush, then backing out slightly to remove the slight compression of the foam and finally driving to flush again.

All of the original wooden windows needed work so they were removed, rebuilt and fitted with glued and screwed 1/2" PT ply flanges to match the plane of the furring strips. The inside edge of each PT flange was extended with a strip of fir for incorporating into the final trim detail.

The XPS came flush with the RO and was taped bottom and sides with Flexwrap and Straightwrap respectively from the foam into the RO. The bottom of the RO was sloped for drainage before the Flexwrap was applied.

The windows were then installed with screws after applying sealant to the back of the top and sides of the flanges. The windows were held about 1/4" away from the bottom of the RO. Then wrap tape (another foam compatible brand I can't recall the name of) was applied to the flanges beginning at the bottom with the tape adhered to the flange and a 12" tall strip of 15 lb felt which covered, but did not seal the gap at the bottom of the window. The tape was then applied across the side flanges onto the foam and finally to the top flanges and onto the foam. A custom drip edge was screwed to the substrate above the upper flange. A shallow 90 degree inward bend at the top of the drip edge was let into a shallow groove in the foam before being taped. The horizontal vents were attached at the top and bottom of the window and brought out to the first vertical furring strip on either side.

A part of the house that ended up with rebuilt walls and new windows was treated the same except for using the factory supplied flanges.

I designed and had made a custom drip edge for the bottom of the wall that went on before the felt. Felt and foam overlapped the metal whose shape bent 90 degrees across the bottom of the foam for insect protection and then straight down (to allow the horizontal vents to lap the foam and the metal) before bending back out at an angle to terminate just inside the plane of the siding at a drip edge.

The Hardie was then applied as described above with only the factory primer and no paint on the backs.

All of the walls have blown in cellulose insulation which was chosen as part of the overall moisture management program for the walls. All of my thinking was informed by the notion that water can and will find its way into the wall.

I've written all this from memory so I could have fogotten something. I hope your powers of visualization are better than my description. But I did end up with numerous 3 ring binders, books, pdfs and notes from chats like this one that served as my original research material. The research was quite confusing since there adamant opinions to support a wide variety of approaches. As just a few examples of my approach I used software to determine dew points in the wall, research that claims that inside wall moisture barriers are a waste of time in the NW marine climate, and various other sources that assisted in choosing 1" XPS as optimum for its particular combination of R-value and vapor permeability in the marine climate scenario.

Finally, I am not a building professional. Just an amateur who got a bit obsessed and finally made a decision after battling months of confusion over all of these issues. There are a lot of photographs of the project. Time will tell if it all works as planned.

[tom struble]

Re: installing fiber cement siding over rigid foam sheathing

hopefully you will post some