Huge siding gaps

I’m doing an inspection of a brand new home with engineered wood lap siding not fiber cement. The gaps are the biggest I’ve ever seen 1/4" with a flashing strip behind the gaps. Is this a new way to install this??

This has been the required/approved (Manufacturer) method of install for a long time. Key here is the materials the siding is manufactured from.


Oh, I’ve just never seen the gap that big. Every time I’ve seen the style of siding in last many years they have had an external auto 1" wide piece of metal covering the seam.

Hardy board siding of something similar uses an approved flashing behind those gaps. Ment to deter warping when the siding expands in warm weather. Not an issue unless the flashing was not used.


Do you know the manufacturer? That is where all the answers are typically found.

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I don’t.

I’ve seen the gaps with flashing in hardie fiber cement but never the engineered wood.

Here is LP smart siding installation instructions. You can jump to page four for gap treatment. I will often use verbiage such as; The siding was consistent with engineered wood siding, I was not provided any additional information. Typical engineered wood siding manufacturers require or recommend blah blah blah.

I see the minimum gap is 3/16" but it says nothing about maximum gap.



As others have said the manufacturer’s specs are what you need. With flashing strips behind the joints it’s very unlikely to ever be a problem but is kind of ugly and will likely come up on future inspections. I ran into this once with Hardie Plank on a new build and ended up talking to the local rep. He basically said yeah, it’s ugly but I’m confident it won’t ever be a problem with the metal flashing plates in place. As an HI just call it out as “abnormal” or whatever term you want to use and recommend consultation with the manufacturer, builder, etc.

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