HardiePlank caulk at butt joints failed -what to replace it with
We chose HardiePlank primed siding for a house we had built in 2006 in Virginia. The builder left a small gap between the butt joints and caulked the space, which apparently was an acceptable practice at that time. although Hardie has since changed their mind and recommends butting the joints. The caulk in the joints is now failing, so I’m trying to educate myself on the issues before I meet the painter. Hardie says the caulk should be elastomeric ASTM c920 class 25 or better but they don’t recommend any particular product. So I’m looking for some recommendations on the best brands currently on the market. Sherwin Williams has one called Shermax that is Class 35 and there’s one called Thermax 920 that is a commercial product with a Class of 100/50. I’m inclined to go for the product with the most elasticity, assuming that will result in the longest life-is that right?
Also, I’ve seen references to the need to have a “bond breaker” so that the caulk doesn’t adhere to the material behind the plank-is this the case?
Many thanks in advance for any help you can provide.
Replies
Your bond breaker would be "Backer Rod", sized according to your gap. You want it tight to put in, but not too tight to fight it.
If you used urethane caulk it would last a very very long time. Might be too messy for this application. Titebond makes a whole line of caulks in many colors. Weathermaster sealant. Meets your 920/cl-25. Good stuff. If you could get the color close-you'd be marginally ahead of the game.
Hardie's Technical Help doesn't help
An addendum to my first post. I called Hardie's technical people and they said they use OSI's Quad Color sealant. But the OSI website specifically states the product should not be used for butt joints http://www.osipro.com/products.pl?id=QUAD . Hardie's tech rep seemed to not believe me and simply restated that ANY C920 elastomeric product will work. Maybe I'm overthinking this ....but I've been burned once. Ha, ha.
Makes me all the more glad that we used metal joints when we resided.
http://www.wlcaulk.com/products/acrylic_latex_caulks_and_sealants/megalastic_super_elastic_sealant/index.html
Nancy,
I am the architectural and application manager for Henkel Corp., the manufacturer of OSI Quad Sealant. Quad is a sealant that is designed for use on all exterior residential siding and claddings. However we do not recommend caulking butt joints.
Although the want to caulk these joints is there, it is not necessary to do so. Aesthetically caulking butt joints looks good for the short term, but over time as you now realize, sealants have a difficult time perfroming in these tight gaps. Weather protection wise, it is not entirely necessary to caulk or seal the butt joints. Water will get behind the siding in many areas besides these butt joints, so to worry about them is not necessary. The weather resitive barrier, if installed correctly, should deflect the water out to the exterior between the sheething and the exterior cladding. In your case Hardie siding.
You are correct in suggesting a backer rod to prevent the sealant from adhering to the sheathing or WRB. These joints are not designed to adequately accept backer rod or sealant. The recommended 1/8" gap between butting joints is not big enought to insert the backer rod or allow for the recommended sealant bead size of 1/4" to 3/8" bead size.
I would recommend leaving the joints uncaulked and simply paint the siding.
-Bill
Just read your post and wanted to tell you about my experience with this product. I used it on a storage barn I built six years ago. I have since found it is VERY sensitive to moisture. If any prt of this siding is subjected to sustained moisture, (like maybe water collecting at butt joints) it will fail. My experience was that my barn had a water table at the bottom of the siding and the builder installed the hardiboard in such a way that it rested on the watertable flashing. Within three years the bottom course of siding was delaminating and had to be replaced! My advice would be to make sure whatever caulk you choose, monitor these areas to make sure moisture is not penetrationg the joint.
What I did with my house, was ...in addition to the paper behind the siding , I shingle fashioned littler strips of roofing paper under the joints.
As Bill said this alone should be enough to turn water and not have any issues with water.
I feel it is inportant to caulk the gaps where the siding buts up against the window/door trim.
I did go ahead and caulk the siding butt joints as well.
I used PL polyurethane and it has held up pretty well for 9 years now. Obviously there are some joints that I had to redo, after a few years.
I could of tried another caulk that streetchs better, but then I felt I might have a paint adhereation problem and the paint might peel at those spots.
So I liked the fact that the caulk I used is paintable ( actually I used a real heavy pigment solid stain). And comes in several colors...we were able to match the color of oue Stain, pretty close.
If NP1 is paintable I'd look into it, that caulk is just plan the most awesome caulk I have ever used.
As far as bond breaker, if your siding subs put in the strips behind the siding joints ( which Is a recommended practice) then that will serve that purpose. But idf the gaps are only 1/8" , I don't think you need to worry about bond breakers...as you shouldn't be jamming in that much caulk in those littler seams.
What kind of paint did they use and how is the paint holding up on the siding and how is it holding up on the joints?
Are you looking to have the house repainted?
Just another voice
I am a hardi products installer and the OSI Quad Sealant product is what is used with Hardi installation. It comes in exact colors that match Hardi products.
Secondly, you can just butt your plank ends as the water envelope behind will shed the water off the wall. Every effort is made to make the siding water tight, but it just ain't so, thats where the envelope (black paper, Tyvek, etc) does it's job.
You MUST chalk where the planks meet trim (window, door, corner, etc).
And Hardi themselves suggest putting small pieces of paper behind the butt joints to help keep water out.