Caulking for hardi-planking

I recently had hardi-plank installed and the builder has given me conflicting advise. First he said I needed to caulk between each horizontal plank where they lap (seems like overkill) and caulk the horizontal seam where two pieces of hardi-plank meet and where they meet the vertical corner board.

Now he is saying that I only need to caulk the vertical seams and where the board meet the corners, and that caulking its the painter's job (the hardi-plank came pre-primed, but not painted), not the responsibility of the guy who installs the siding.

What's the correct answer?

 

You don't caulk horizontal surfaces. Water has to run somewhere. The vertical surfaces at corners, etc need caulking. Did they put WRB under each connecting seam as they installed it? Best practice. Caulking is usually the job of the painter. Ask Mark, as I believe they don't like others botching up jobs that they have to redo. However, cost is an item, and it may matter to some painters. The ones I deal with forbid me to get out a caulk gun

 

I always prefer to do my own caulking! that way I know it's done right. I couldn't tell you how many times a carpenter has told me "I had a bad joint but I caulked it for you" and I had to remove the caulking so I could get the joint presentable enough to paint. Less work for me if he had left it alone.

Do you have a professional painter coming? or will you be doing the painting?

 

Thanks Chandler and Mark. I don't know what WRB is, but I know they did not install it because I watched put up the hardi-plank. I will be doing the painting (and the caulking)- I painted houses in college during the summers, but any tips you can offer would be appreciated. For example I plan on picking up exterior silicone based caulking....

 

Google is your friend: WRB = Weather-Resistant-Barrier (IE: Tar paper, felt, Tyvek)

 

You don't want to use pure silicone caulk - it's not paintable! You'll want to use something along the line of a siliconized acrylic latex caulk which is paintable. My favorite is White Lightning but there are other good latex caulks that you could use.

 

Check the instructions for your brand of fiber cement online, since there are specific guidelines (ASTM testing) that the caulk should meet. OSI Quad is probably my favorite but it is not a painters caulk that you tool down to nothing.