Thread: Hardie Plank siding

"This Technical Bulletin is an explanation supporting the announcement made by James Hardie on September 8th, 2008 withdrawing its recommendation on the use of caulk at field butt joints for HardiePlankTM lap siding."

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JP: Though I understood their reasoning all along, the presence of the flashing can simply not be verified after installation. Additionally, any cut butt joints are almost never primed. If they are not caulked, the presence of flashing will not have the effect of sealing them as caulk does.

Originally Posted by Jerry Peck

"This Technical Bulletin is an explanation supporting the announcement made by James Hardie on September 8th, 2008 withdrawing its recommendation on the use of caulk at field butt joints for HardiePlankTM lap siding."

You can still use caulk on the regular lap siding if you wish. It will not void the warranty.

"HardiePlank lap siding Primed - Recommend the use of joint flashing, but the use of caulk will not void the warranty.

You can still use caulk on the regular lap siding if you wish. It will not void the warranty.

TM: True, but that does not speak to my point concerning how one should go about ascertaining the presence of the flashing once the siding is installed. The caulking is optional.

Originally Posted by A.D. Miller

TM: True, but that does not speak to my point concerning how one should go about ascertaining the presence of the flashing once the siding is installed.

I have always been able to find a few joints that are wide enough to look into and see if there is flashing or not.

For awhile, one builder here was not installing flashing or caulking the joints. They did not immediately grasp why that was a problem until after some discussion.

And Jerry, thanks for the updated bulletin. I had not heard that caulk was not allowed with the prepainted siding.

Originally Posted by Lou Collier

For awhile, one builder here was not installing flashing or caulking the joints. They did not immediately grasp why that was a problem until after some discussion.

Obviously not an "expert" at their business.

From that technical bulletin:

Experts across the industry recognize flashings as an effective and responsible method for draining a wall system:

“The fundamental principle of water management is to shed water by layering materials in such a way that water is directed downwards and outwards out of the building or away from the building. The key to this fundamental principle is drainage. The most elegant expression of this concept is a flashing. Flashings are the most under-rated building enclosure component and arguably the most important.”

EEBA (Energy & Environmental Building Association™) Water Management Guide By Joseph W. Lstriburek, Ph.D., P.eng. June 2004.

(Yes, they misspelled Dr. Joe's last name. )

Obviously not an "expert" at their business.

JP: Or, and expert builder from Texas.

Yes, they misspelled Dr. Joe's last name.

JP: That could be pretty easy to do. It is, however, easier than pronouncing it right.

All you have to do to verify flashing at butt joints is to slide your screwdriver in near the joint, twist or pull lightly, shine a flashlight up, and the flashing will be visible.

When is the last time someone saw a large enough gap at butt joints to comply with caulk manufacturers installation instructions? I wonder why the caulk fails quickly?

I usually see caulking at butt joints in my area. As with all installations, the end result has to do with the skill and pride in workmanship of the installer - these days I'm not impressed with either. I discuss the caulking/maintenance issue with buyers, but I sure wish flashing at all butt joints was always the norm - homeowners just do not "Do maintenance", as stupid as that is. Thanks, Jerry for the heads up!

Some contractors make it easy for inspectors to see in the joints.

What is an H section joint cover? Just thinking about it, Im envisioning an H, with the ends of the hardy plan shoved into the open ends (e.g. a horizontal H, with the outer bars kind of acting like a batten. The instructions say you should caulk, prior to putting on the H section joint cover?


I dont think I ever see H section joint covers in these parts.

Oddly enough, my neighbors are just getting hardy plan on the gables of their house last weekend. They are caulking the bejesus out of the ends. The crew doing it looks like the usual suspects hanging out in front of Home Depot in the mornings.

I dont think I ever see H section joint covers in these parts.

They used to use those things on some hardboard siding.

Something similar to figure 2 of this: http://www.variform.com/NapcoWebDocu...stallation.pdf

They look exactly like this:

http://www.tamlyn.com/documents/INSTALLSUGG.pdf

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