David Asks: Are there industry standards for the horizontal alignment of cedar siding boards? We had a home remodel and new cedar siding had to be installed on some of the exterior walls. The horizontal siding aligns evenly at the bottom of two adjoining walls however part way up on one wall, they decreased the overlap of each board and now the horizontal siding on one wall is out of alignment with the siding on the adjoining wall by as much as 3/4” to 1-1/4”. Even though we have wood corner boards on each corner, this is very noticeable. I was told that the contractor was cutting corners by not replacing all the siding on the one wall, and the decrease in the vertical overlap was needed in order to meet up properly with the old siding they did not want to replace. Therefore I am wondering if there are industry guidelines and best practices that cover this type of situation?
Steve Bliss, of BuildingAdvisor.com. responds:
The standard practice is for each course of horizontal siding to match the next and for boards to line up at inside and outside corners. Sometimes, in remodeling, it is necessary to fudge this a little to “match existing” or to blend old and new. However, where the contractor must improvise a solution, he should discuss the options first with the owner – especially where the variance will be readily observable.
Also if he is decreasing the overlap below the recommended minimum, you will be risking excessive intrusion of water at the overlap from windblown rain and capillary action. The recommended overlaps for different siding profiles are shown in the attached siding manuals.
In the building industry, most industry guidelines for the installation of materials come from trade associations and manufacturers. Building codes, on the other hand, cover safety and structural standards, but have little to say about the quality of the workmanship.
The main industry guideline for wood siding installation is the WWPA’s Natural Wood Siding. A similar guide How to Install Western Red Cedar Siding (by Western Red Cedar Lumber Association), is largely based on the WWPA guidelines. While these guides don’t specifically address the alignment of siding, they both show details for corner installations, with and without corner boards, which clearly show the two sides lining up at the corner. These guidelines are attached.
The National Assoc. of Home Builders (NAHB) publishes a general set of quality standards called the Residential Construction Performance Guidelines . These are consensus standards among members of the homebuilding industry and should be considered minimum standards for workmanship. The guide states, on page 30:
5–1–3 Observation: Siding is not parallel with the course above or below. Performance Guideline: A piece of siding may not be more than ½ inch off parallel with contiguous courses in any 20-foot measurement. Remodeling Specific Guideline: The contractor and consumer may agree to install siding to match existing conditions on the existing structure and to disregard the performance guideline for this item. If the contractor and consumer have agreed that the floor of an addition is to be on a different plane from an existing floor (e.g., out of level), the siding on the addition may not be parallel and in line with the existing siding.
I can’t say specifically why your contractor took the approach he did, but your explanation is certainly plausible. I’d suggest asking him – and if you are not satisfied with the answer – request that the work be redone correctly before making the final payment. If he claims that the work meets normal industry standards, then you might want to share this material with him.