BCAB #1462 - Wood Columns Below Grade & Support of Sidewalk, Article 18.104.22.168.
April 14, 1998
Re: Wood Columns Below Grade & Support of Sidewalk, Article 22.214.171.124.
The project in question is a new single family dwelling. Stucco-clad wood posts supporting an open sundeck sit on concrete foundations which are below finished ground level. The top of the concrete is about one foot below the grade level concrete patio which is below the sundeck. The untreated wood posts project through the patio to the footing. Posts supporting the roof above the main entrance are supported in a similar way.
There is a concrete sidewalk adjacent to the house that is pinned to the house foundation. Settlement of the ground adjacent to the house has caused the sidewalk to drop at the outside edge but the pins keep the sidewalk at its original elevation next to the foundation.
Reason for Appeal
Article 126.96.36.199. requires foundation walls to be extend not less than 150 mm above finished ground level. Article 188.8.131.52. requires untreated wood framing members supported on concrete to be separated from the concrete by polyethylene or roll roofing unless the wood is at least 150 mm above the ground. Article 184.108.40.206. requires stucco to be at least 200 mm above finished ground level.
The appellant considers the below ground wood columns to be unacceptable and potentially dangerous. The wood will deteriorate in contact with the ground and the deck could collapse. The stucco near the base of the column has already cracked because of the wood expanding due to moisture absorption.
The appellant also considers the attachment of the sidewalk to the foundation wall to be detrimental to the building structure because the concrete resting on the ground is subjected to different movements than the structure supported on the foundation (due to freeze-thaw cycles).
Building Official's Position
The building official agrees that the untreated wood posts being below finished ground does not comply with the code. However, the official is prepared to accept a preserved wood post conforming to CAN3-S406, "Construction of Preserved Wood Foundations," as referenced in Sentence 220.127.116.11.(3). This provides the simplest solution and still meets the requirements of Article 18.104.22.168. for lateral movement and uplift restraint.
The code does not address the design or construction of residential sidewalks and neither requires nor prohibits their attachment to the building foundation.
Appeal Board Decision #1462
It is the determination of the Board that the proposed solution of using treated wood posts conforming to CAN3-S406 does not conform to the code. Article 22.214.171.124. is not applicable to this situation because the wood post is not a foundation. CAN3-S406 describes the construction of a wood foundation system and includes much more than just the use of treated wood. The Board considers that Articles 126.96.36.199. and 188.8.131.52. are applicable to the sundeck support posts.
The Board does not consider the exterior sidewalk or patio to be regulated by the code. The effect of the sidewalk's connection to the foundation wall would be regulated by Article 184.108.40.206. unless it can be shown that the connection has no structural effect on the foundation wall.
George R. Humphrey, Chair