Cement Board Siding Seams

Pretty much all trim joints need to be sealed.

Cement board siding seams.

This has proven problematic over time as caulking the joint results in unsightly surface appearances due to the different textures as well as resulted in failure of the caulk joint and associated ongoing maintenance. Weatherside fiber cement siding is the 1 and weatherside fiber cement siding is the 1 and only solution for replacing or repairing old asbestos siding shingles. James hardie believes it is good building practice to seal the joints to prevent moisture such as wind driven rain and snow from penetrating the wall cavity. In this video i show you how to tape cement board joints.

Buckled fiber cement siding is most likely to occur because the installer failed to give the recommended gap between the ends of the fiber cement boards and abutting vertical trim at corners windows doors etc. This article series includes field reports of fiber cement board lap siding butt joint gap. Traditionally board and batten siding starts with wide vertical planks boards which are then joined together by thin vertical strips battens to cover the seams. Some manufacturers do not require the metal flashing therefore we caulk the butt joint to keep the pieces together and also prevent moisture.

It is a very simple process and i used some fibatape and thinset mortar to seal the cement board j. Hardieplank the classic flagship james hardie product is a simple 5 16 inch thick by 12 foot long lap siding in widths ranging from 5 1 4 inch to 8 1 4 inch. We only caulk butt joints on cedar siding if previously caulked. Homesteaders and farmers would use sawmills to cut the long boards and the battens were put in place to make the structure as airtight as possible.

James hardie 8 25 in x 144 in hz10 hardieplank cedarmill fiber cement lap siding. Manufacturers caulk and sealant recommendation sheet s 100b issued july 2000 application. For pricing and availability. Fiber cement boards are caulked only when there is no metal flashing behind them.

We can see a hard dried layer of caulk that was a bit under 1 8 inch wide inside of the now wide open butt joint between two siding boards. Trim boards wood windows. Our siding close up photo at page top illustrates what may be another clue in the history of a failed installation. It does nothing else but produce fiber cement siding and cement backer boards.

A common problem with cement board siding products and some other types of horizontal lap siding is that older installation guidelines called for caulking the joint instead of flashing the joint.