Gaps Between Hardi Plank Siding

James hardie recommends the use of caulks and sealants that remain permanently flexible.

Gaps between hardi plank siding.

In contrast caulk manufacturers specify a minimum gap at butt joints which can become more visible as the caulk ages. When james hardie siding products butt into wood based materials a 1 8 gap will allow for expansion and contraction of the wood based product. This is a common mistake and so easy to avid. The boards would shrink a little bit making the gap 3 16 to 3 8 depending on how much moisture was in them and how close the install gap was to 1 8.

But the siding should never hang below the trim. 16 or 24 on center let in bracing weather resistive barrier fastener 1 4 thick lath strip moderate contact or maximum 1 8 gap. When installing the first course make. Flashing installed incorrectly or siding installed without the proper gap between the siding and flashing will both result in water damage and a voided warranty.

Gap between the siding and trim. 3 8 from plank edge leave 1 8 gap between plank and trim then caulk weather resistive barrier plywood or osb sheathing. Always caulk between the siding and the trim. Hardie siding requires a minimum 2 gap from all hard surfaces like decks or rooflines and at least 8 from any soft surfaces like grass dirt or gravel.

Always prime or paint any cut edges that are inserted into a window j channel. It is also difficult to achieve the specified gap in the horizontal overlap. The bottom of the siding should be kept even with the bottom of the trim or if desired the trim may extend below the bottom of the siding. During my time working for james hardie i very rarely got calls from homeowners that wanted to submit a warranty claim for their hardie siding.

James hardie recommends the use of caulks and sealants that remain permanently flexible. James hardie recommends butting field joints together in moderate contact to achieve a continuous looking joint. High moisture at time of installation is going to give gaps. 10 years ago the installation directions called for an 1 8 gap and then caulk.

If siding butt joint gaps are due to shrinkage the central problem is one of shrinkage that occurs principally if the siding was not stored properly prior to installation particularly if it got wet. Remember that most hardie siding problems are caused by improper installation. Double wall construction single wall construction. Leave a 1 8 gap between the siding and the trim or other materials to allow for structural movement.

Vertical trim gap caulking.