Thought I could find this in the achives, but no luck. Installing Hardiplank on my house (first time w/ Hardi), and I think I’m pretty dialed in. Double-checking the Hardi literature it says the distance between the end of a plank and a trim piece should be an “appropriate gap”.
Hmmmmm. Appropriate gap. I’m thinking that, since Hardi end-to-end can be in moderate contact, 1/16″ to 1/8″ would be appropriate. Yes? No? Why? Thanks.
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Replies
Red,
I use an 1/8, it makes sure the caulk gets between the plank and trim. Use a good caulk
Thanks. Do you caulk each course as you go or wait and do the whole wall? I'm thinking of doing each course - overkill?
I carry a few 1 1/4" stainless trim nails and tap one in just above the lap line to set the gap.
A bonus is not having to measure or guess the gap and when hanging solo it is a friction point that holds the end of the board firmly in place against the corner board or previous plank without resorting to homemade or purchased hanging gauges.
I pull and reuse the nails as I go along and if there is an end that won't lay down I have an instant, unobstrusive face nail for the offending corner.
Do one job at a time. Save the caulking until the end.
Edited 10/22/2007 12:55 am ET by RalphWicklund
Ralph, I was liking your idea until you got to the "I pull the nail" part.I guess I'm somewhat hesitant to automatically create a small pinhole, through the secondary water barrier at every joint. Have you considered this and is there some way that you seal these small holes? fka (formerly known as) blue
Note that I said the nail is ABOVE the lap. In the 1 1/4" space that will be covered by the next board.
When I caulk the joint some of the caulk will be forced up under the lap at that point. There is no way water is going to go uphill to find that pinhole.
I did note that you said "above" the lap. And I was envisioning a tiny pinhole in the joint, not exposed to the weather. I also envision no way of definitively sealing the hole unless you seal each pinhole as you pull the nail.I know it's not a lot, nor really a big deal, but with the mold issues what they are....That hole represents to me a direct entry point that driven rain could find. I'm thinking of the capillary action of water running along the horizontal siding. It hits the caulk glob and migrates up behind the joint. Once there it seeks the path of least resistance and finds the open gap of the siding above the glob of caulk. After filling that gap, the water is pulled into the nail hole.Oh my....I'm way too deep into this. It just strikes me as exactly where I wouldn't want a pinhole. Maybe Im just paranoid. fka (formerly known as) blue
Yep. Capillary action. Driven rain. Water migrates up beneath each and every board, collects on top of every lapped board in that 5/16" space that runs the length of the building. Multiply that by the number of boards with a potential for a river of water pooling along each top edge and then seeping, via gravity, wind pressure and CAPILLARY action down behind each board and then finding a nail every 16" or so stuck thru the underlayment.
Yep, you're paraniod.
However, that might be a topic for the building science people to explore. How many pinholes from various sources and at various locations constitute a hazard to the well being of the sheathing and then the building.
To continue, I have a solution to the pinhole which does not involve changing gears to handle a caulk gun after every stick. Every joint is backed with a swatch of felt before the final end nails are driven. If I give each swatch a slight sideways pull when I remove the trim nail the hole will disappear. Likewise, if I put the swatch in after I remove the spacing nail then there is no hole to wick water.
Nah, now I'm paranoid.
Ahaaaaa! The old felt trick! I'm not actually paranoid but I notice that when I'm working I do avoid things like we have just discussed. I wouldn't put that nail in just because it is my nature but I wouldn't ask anyone else to avoid putting the nail in because once I think about it, I'm actually not worried about it! I can't help myself....I admit...I guess I am paranoid after all.fka (formerly known as) blue
Like stated above you want enough of a gap to make sure the caulk can penetrate the gap rather than being just smeared on the surface in a thin film.
BTW - you said >> I'm thinking that, since Hardi end-to-end can be in moderate contact... << I'm aware that is what the instructions say but I wouldn't do that if I were you. 1) again, the caulk needs to penetrate the gap and 2) it leaves no room for expansion. I've seen cement siding jobs where there were no gaps left at the end to end interface, and on a hot day the butt ends of the "boards" were all puckered out (for lack of a better term) and looked like total sheet.
One time, we were doing a frame for a new builder and he had Hardi. Before we started the Hardi work, we checked with him to determine how he wanted the joints....gapped, tight, or backed with something special or whatever....we don't care.He tells us to gap them, because they'll get caulked later by the painters or whoever. Predictably, his superiors come by a couple weeks later and complain about the ugly joints and caulking in them. Thereafter, we were never allowed to gap them again for that builder. When in Rome....fka (formerly known as) blue
I should have gotten a pic on the 'looked like sheet' job...
Over the years, I've learned not to bother.
One of my first experiences with "faux" siding was when we did a LP job. The super wanted us to countersink all our nails and we were face nailing just like we used to with the old"'real wood" lap siding. He even went around after we were done and pointed out several that were only flush and he made us go up a ladder with a nailset to sink them.
He told us that the painter was going to fill them all before rolling it.
A year later we were back there for some reason and the house was done and there wasn't a single nail hole filled!
Like I said, over the years, I've learned to not even thing about it. If a builder wants something goofy, we'll do it.fka (formerly known as) blue