[scot patterson]

I have read several of the postings here about installing hardie plank siding. Here is some information you may find interesting.

For those of you who have been tracking it, Hardie Plank recently changed their recommendations regarding field seams. Two years ago, they advised spacing field seams 1/8" apart, now they are saying "moderate contact." I emailed their customer service department and asked if they had any data regarding expansion and contraction of Hardie Plank siding due to temperature and moisture. They responded that their siding was dimensionally stable compared with other siding products, they had no data. How can this be? How can you say the product is comparable when you have no data? Perhaps more importantly, why doesn't Hardie Plank have any data?

Being resourceful, as contractors are known to be, I took some 12 ft. siding to a commercial walk-in freezer. I froze the siding down to -10 degrees, removed it from the freezer, and blocked both ends on a backing board. It was a warm day, about 95 degrees. When the siding warmed up to air temperature it had buckled off the backing board by and inch and a half! It had expanded approx. 1/16"+. This suggests that their recommendation of moderate contact with field seams is problematic, particularly if the siding is installed cold. We found similar expansion when the siding was exposed to moisture.

Don't get me wrong, I think Hardie Plank is a great product. I installed it on my own house. But why are they giving contractors such poor information? Haven't there been enough law suits over failed siding?

One other note. I think you should always predrill the corners at the end of each piece of siding. I have heard of failed siding jobs due to the corners cracking. Just use a standard drill bit. When it gets dull, break a piece off the tip. A broken bit actually works best.

Hope this is useful.

 

[enforcer]

Scott
are you saying the 1/8 " seam should still prevail?

 

[NormW]

Nice post, gives me something to think about. Wondering what the expansion would be if the original temp was in the low 20s. Next time I use it during the winter, I'll be sure to gap the seams, and caulk the corners.

Best thing about this post, is I have a good excuse not to install hardi-plank in sub-zero temps! :thumbup: I do work all winter long, and I often wonder how the work I do in winter compares with fair weather stuff. On the converse I find azek that I put on in during summer months with gaps so large, I can see them from the road when I drive by. :shutup: Yes, I use the glue...

I moan about the problem to customers everytime I'm asked to use azek... so they've been warned.

 

[Kenm]

Good eye to catch the change! You bet they have the data, just not willing to share. I think you will find the moderate contact instructions are geared towards Colorplus Hardie which requires slip sheets behind the joints. Here in Florida I have yet to see any problem with contraction and expansion.
Predrilling the corners? Not needed if you hold the nails off the edge as recommended.

 

[MJW]

The data will come out if they have warranty claims to cover their butt.

Like I've said before, this stuff just isn't what it's all cracked up to be. pun intended.........

In the south it may work better, but that's a risk someone else can take, not me or my customers.

 

[jumbo]

Good post. I've been installing Hardi all 12 months for years, I've never had a problem with expansion. But certainly doesn't mean I wont in the future. I too pre-nail all my ends and hand nail. Pretty tough to follow their setbacks and still hit stud. The vast majority of repairs on cement we do is what looks to be from breaking of ends. That being said, I've always wondered if it happened from poor nailing or from expansion and contraction.

 

[ApgarNJ]

It also depends on the moisture content at the time of install. I did a job this past summer using prepainted 8.25 hardie. the pallets/bundles were prewrapped with hardie's plastic etc. I had a tarp over it at all times, and we installed with very minimal spacing. It dried once hung on the walls and the gaps are even bigger now. the HO is not complaining but I wasn't happy with it. If it's cold out the I will leave a small space but for spring and summer, I'm going to butt them tight. I guess the pieces we used on that job were too moist and dried after we installed. I also know a guy who installs them tight to corners, windows etc. and has never had an issue and he's been doing it for years this way. it cuts down on how much caulk you need as well. They changed their tune from the earlier days of saying leave 1/16 gap at each end, including butt seams in the field.

 

[Tom Struble]

i gotta agree with that,i think moisture has maybe more affect on hardi shrinking issues than temperature