Fiber cement siding from the 40's & 50's did contain asbestsos but Hardi plank siding of today does not, it is made up of portland cement mixed with ground sand, cellulose fiber, and other additives.

I can not speak to moisture issues, but have not heard of that problem before unless there were a lot of other water issues not related to the siding.

I strongly suspect the moisture issues would have arisen regardless of the type of siding. We shouldn't blame Hardie or vinyl or anything else if the installation wasn't done properly, and if you read all posts you'll see that improper window installation [allowing leaks and condensation] is closely followed by improper underlayment installation.

Cement siding and stucco finishes are indeed quite different from wood, and the installers must know the proper underlayment procedures. That said, Hardie/Certainteed (and similar products) have fairly precise instructions for "how-to" installation which should be followed closely to maintain warranty validation. The problem arises that even when directions are understood [and they often aren't], there seems to be an attitude among some crews that "close enough is okay" and "so what" about rips and tears... which means you are dependent on someone else to oversee the quality of every step of the installation.

I can't reassure you that you'll find a good and knowledgeable crew, but I would certainly suggest that you look closely at their past work, especially those houses that are 3 or more years old. But never forget that mold and mildew issues are usually reflective of water leakage caused/permitted by something other than the type of siding.

I have seen many houses in my area where the hardie cement siding has discolored - from the roadside it does look like mold. We had some mold growth on our hardie siding and in the spring we powerwashed it. I cannot believe that "cement" would mold.....perhaps it was the paint (it was painted on site). I do live in a "humid" area. I am debating on whether to use it on our new home.

It doesn't have asbestos. But if you cut it with a saw, the dust is nasty (the silica is considered carcinogenic). There are several tools out there intended to cut w/o generating dust (fiber cement shears, etc). Or you can use an appropriate respirator when cutting.

Any type of siding will mold in the right climate, especially on the shady side(s) of the house.

(How do you find your way in a Florida cookie cutter subdivision? It's easy. The mildew grows on the north sides of the houses.)

I should have been more clear.

The mold (I am told) is between the cement and the structure of the house. Unlike brick I am told, there is no/little/less air circulation area between the cement and the structure. I was also told that the cement does not allow the moisture to escape as well or like vinyl/brick/etc. Therefore, I was told that mold and rotting structures (between the cement and the interior walls are now becoming a problem?????

It is very important to seal vindow/door/joints/etc. when doing maintenance. Maybe the mold/rotting wood is a result of owners/builders not doing correct maintenance on their homes???

Heartland has produced literature that details why they (a vinyl company) believes that cement siding is not a good choice. I am sure that if you took any literature from any product and dissect the details it would seem more disturbing. I have attached a link to the literature that Heartland has produced.

I love the look but.....I plan to do further reserach. Take a look at the literature and I would love to hear your thoughts before I make my decision! Thanks, this is such a great place to find out from the experienced what you think!

Thanks!

Here is a link that might be useful: The Real Story About Fiber Cement

When a product manufacturer devotes the majority of his advertising space to slamming a competitor, it reminds me of the slimy politicians that do the same thing.

Some of the stuff they point out is ridiculous. Of course the siding manufacturer isn't going to warranty someone else's paint. Of course transparent and semi-transparent stains fade. That's a limitation of stain. It has nothing to do with the siding.

The only thing that brochure has done is to convince me not to use Heartland products.

It's not so much the cement not allowing the moisture to escape, but rather holding the moisture not allowing to dry. This is true with wood sidings as well and is the reason back priming and sealing all cuts are important. I was recently informed on another thread that certainteed fiber advises not to back prime fiber cement sidings. I think i would re-think that. The proper install is to install the siding on strapping over the underlayments/flashing in order to leave a drainage plane and as mentioned above, allow air circulation. This allows moisture to run down and out. In california, the strapping technique is not allowed as the strapping must have an upper and lower horizontal "plate" for fire stop reasons. On Rollie's bog, the delores house, i believe the strapping technique is explained in detail. Here's a past thread on the subject that has links to the delores site as well as others:

Here is a link that might be useful: rain screen

If the fungus is occurring in the wood structural wall behind the weather resistant barrier (underlayment) is probably due to a faulty wall design and not whether the siding is fiber-cement, wood, or vinyl. You are most likely hearing stories from the competitors of fiber-cement siding which is a testament to how well it is doing in the general market.

Fiber-cement is a moisture reservoir material but it isn't anything like brick. Such materials are a problem because in a humid climate, in the sun after a rain, moisture is driven back into the house. In these conditions the wall is usually designed to dry to the interior (no interior vapor barrier).

In more northern climates, as a precaution, I would recommend putting Hardie products on strapping or a draining wrap and using capped nails and taping the wrap at ALL joints like the instructions say. Even better would be sheathing with a factory or field applied liquid breathable weather resistant barrier.

If you are installing this product yourself be sure to wear a good mask and read Hardie's recommendations about HEPA filters for the saw or figure out how to make their score & snap system work for you.

The strapping method could also benefit dry/hot climates combating heat gain. Strapping over radiant barrier kraft backed underlayment would restrict the heat gain to the air space between the siding and the radiant. The heat travels up and out the soffit/ridgee venting. This would have to coincide with the proper install of radiant barrier in attic and cathedral ceiling areas for a complete envelope.

Unfortunately, even in very hot climates radiant barriers on walls do not pay for themselves very fast but they can't hurt.

There are a lot of discussions on the internet about applying fiber-cement over strapping.

This is not exactly on-topic but close enough that I think you all will be interested.

I recently learned that one of the big things causing mold is improperly installed house-wrap. It isn't rocket science to put up Tyvek or other air/moisture barriers properly but apparently a lot of builders don't pay any attention to the house-wrap specs. They just slap the stuff up and put siding over it and the owner is no wiser... until they start having mold problems.

Dupont - who makes Tyvek - has gone to the effort of making "housewrap specialists" available in all areas who will come out to your build-site for free and advise on exactly HOW to properly install Tyvek.

I know this because when my builder's sub put the Tyvek wrap up, it didn't look right to me - way too many staples and those that were used looked too small, lots of patched together pieces, lower sections over the top of upper sections so that water would be funneled between the layers of Tyvek, vertical seams with no taping, etc. etc. etc. So I went to the Dupont website and pulled up the specs for Tyvek house-wrap and read them.

Needless to say, this precipitated a major fight between me and my builder who insisted that his sub had put Tyvek on "hundreds of homes" and that "he knows what he is doing" and "there is more than one right way to put it up" and "I'm the builder, you should trust me to know what I'm doing" etc.

In desperation, I contacted Dupont and they gave me the phone number of their house-wrap specialist in my area. I called him at 4:30 PM and he told me he would meet me at my house at 8:30 the next morning. He arrived and took one look, and immediately told my builder "this will NOT do, your installation voids our warranties and if you slap hardiplank over this mess, it'll be a wonder if the homeowner doesn't have mold problems inside of three years." Since my contract requires my builder to follow the specs of manufactured products so as to not void any manufacturer's warranty, that gave me the clout I needed to get my builder to make his sub do it right!

The Dupont house-wrap specialist stayed at my site about 3 hours that morning advising the subcontractor and his workers on exactly what needed to be done to fix the job. He then made 2 more trips to out to inspect and finally sign off on the Tyvek installation.

Since he had to travel nearly 40 miles (one way) to reach my house, I figure he put in close to a full day assisting with my build. And it cost me nothing so I know there is no way Dupont could have made any profit whatsoever on the house-wrap that went into my house.

On his third trip, I asked him WHY Dupont would bother. His response was that it wasn't just my house that was affected but potentially every house that my builder and that sub and even any of his crew worked on in the future and that Dupont saw educating these people as the only way they could protect the integrity of their product.

I have to say, I was impressed and wanted to share the information. I'm now reading the installation specs on every product that goes into my house and watching to see that they are followed and, if they're not, I'm going to be calling the manufacturer pronto.

Thanks for all the comments...more to think about. cpate, very interesting comment. Unfortuately in rural communities we do not have as much access to representatives from some of the companies we use. That's why this website has been so helpful to me as we just begin to build!

Thank you for posting that. It is scary and reassuring at the same time, but is good to know.

Our builder has been using the "hardie/cement siding" for years and swears by the product. I think it is the Certainteed siding that he will be using on our house. He did make a comment on the right way to apply the house wrap and the siding so I could see how if those two things were not put up correctly there would be a chance for moisture to get between the surfaces. I would have to agree with frog_hopper about Heartland slamming the competition; that is just bad advertising IMO.

sallen2008 ~ don't discount the availability of manufacturer's help just because a build is 'rural'. 96% of the USA is rural, and I doubt distance will hinder a reputable manufacturer!

As pointed out by the Dupont rep, it isn't just your house, but every other house built using their product which will be affected by the knowledge [or lack of]. Word-of-mouth is important and word-of-web is influential too; the best of the manufacturers are willing to go quite a distance because they know how important it is to build and keep their reputation. OTOH, we as the builders have to be willing to make the effort to get the manufacturer involved.

meldy nva, how right you are!

Top-notch builders make sure their sub know the right way to use manufactured and that they are uding them properly. Unfortunately for homeowners, there are too many builders out there who blindly trust that their subs know what they're doing and then expect the owners to trust them to make sure it is right. Talk about the blind leading the blind.

The homeowner is the one who will ultimately be harmed so the HO needs to be reading specs for him/herself. You don't have to get to where you understand everything but you do have to get to the point where you understand enought to spot the glaring mistakes - and find them before they get covered over with the next layer!

Or, as I told a cousin: I can't hammer a nail worth a d4m, but I know which ones are supposed to go where.

It's probably safe to say that no sub and no contractor is going to be as concerned about your house as you will be, and few of them will take the time to study the specs, so you had better do it. You don't have to turn the screws, but you should know which ones need to be turned.