I am doing my siding on my new house myself. I am quite capable of doing it. I was told that
I would need 2 cases of caulking cause you have to leave a 1/8 space at each joint and fill it with caulking. Then I was told to nail it solid to a stud every 16". If it were going to move shouldn't you have nail it like vinyl. I took a drive and even walked around other houses and seen that the nicer jobs seem to be tighter joints. Not saying there isn't any caulking but you don't need 2 cases per job.

Don't know who told you that but there wrong. You need to make your joints up tight, caulking is for painters not carpenters. Hardi board doesn't move, its concrete.

Glavine's correct, wood may expand and contract but Hardieboard is very stable. When we use Hardiebacker for bathroom floors and walls we butt the sheets tight.

I have used 2" fiberglass mess tape on the seams of Hardibacker on both shower and bathroom floors, but the sheets of Hardibacker were butted up against each other with no gap whatsoever.

I think you are speaking of two different products here. Hardiboard siding and hardibacker underlayment.

Harold, you are correct but both are made by the James Hardie Company, same material characteristics.

Some people like to caulk the cut seams and then they should be pushed tightly together. As it helps to repel water and keep it from getting behind the planks. But I don't think you have to if you have proper house wrap.
However, the Hardieplank or similar product technical documents would give you the proper information if you're so inclined.

I just watched This Old House guys working down in New Orleans. They did butter the ends of each plank with caulk and then butted them tight. I've heard Norm says he likes to do this or it's a best practice.

Thanks Bob,

I didn't know that. My sister's house has Hardiboard siding. I knew that it was composition board but didn't know it was same as underlayment.

Bob,
If Hardiboard doesn't expand and contract, how come juthrow over on the Exterior Home Improvement is having such a hard time with caulking?

EVERYTHING expands and contracts with changes in temperatures, even metals and concrete and fibreglass.

But it's not wood and it doesn't have grain. So it would expand all around not just the seams. It's possible it might only expand very minimal amount. But why doesn't he read the technical documentation on the site? Or call Hardie for a definite answer?

He could have issues because of when he's doing the caulking and what he's using. It should be manufacturer recommended and at the correct temperatures.

And both Hardiboard and Hardibacker use a fibreglass cloth to hold the concrete together during curing. They are possibly different mixtures. One to cope with extremes of cold and heat. While the other is more useful for a temperate controlled climate.

Harold, I had not read about that guys so I went there and asked a few questions.

We installed certainteed siding last year. Its like hardieplank but with a nicer grain.

Here is a cut and paste from the installation directions:

FiberTect-sealed lap siding with factory ends should be installed with joints
Butted in moderate contact. Caulking is not necessary. Cut ends can be
Sealed or painted, butted in moderate contact, and NOT caulked. If you
Prefer not to seal or paint the cut ends, gap the joints 1/8" and caulk.

So it appears you can do either... we choose butt joints and no caulking for the reasons that glavine gave earlier.

Hey Eric - if you're doing it yourself, you should buy a pneumatic siding nailer. It's beefier than a finishing nailer but a lot lighter than a framing nailer. I got the bostitch coil siding nailer - but I think just about all tool mfg's makes one.

We used the superduper extra hot dipped galvanized siding nails... but if you have any time at all, you may want to search around for stainless nails. I could not find them easily in the local stores, but they are available on the internet if you have time to order them. I can't think of anyting worse than looking at rust stains from crappy nails on my siding in 15 years!

Oh - a few more things. You'll still need one or two helpers. Its like trying to lift wet spaghetti and it will break if you give it half a chance by holding it the wrong way. We had three people: one cutting & passing up pieces, with two holding and nailing from scaffolds. Dust masks are mandatory when cutting & make sure you close all windows/ cover outdoor furniture etc.

Thanks for all the tips... I bought the Siding holders and they work great. Like having another guy on the end. Unfortunately I am doing it by myself so is a little harder. I have 6 sections of scaffold and 5 planks so I have a good working platform. It's slow but it's for myself and looks good. I don't mind taking the time if the result is positive.