« Inspector Committee Update | Home | SOP Update Files »
Installing Sill Plates and Posts at Exposed Columns
By Edward Robinson | July 25, 2008
A common occurrence in new construction is improper installation of column details in exposed areas of front and rear porches. I frequently find wood columns or column assemblies at exposed locations that rest directly on the surface of concrete porches or patios at the foundation, or worse, those in this configuration that will be surrounded with brick siding. Brick siding does not provide protection from moisture, and in many cases, the brick will hold moisture at the base of the column assemblies.
The bases of columns constructed so that they rest on exposed concrete surfaces in my area are subjected to frequent wetting and may deteriorate prematurely. Most plans call for the use of a curb of concrete and, where brick exists, require the use of a brick ledge to hold the structure above surfaces that will be wet; however, this is normally considered too much trouble by most builders. In areas where there are wind load considerations, galvanized anchors that also hold the structure above the surface of wet surfaces may be an acceptable substitute for curbs. With regard to constructing curbs to support columns, I have been told by more than one builder on job sites that it is too much trouble or that they don’t build them that way. This translates to “we don’t build quality.”
Where wood is allowed to rest directly on the surface of the concrete and at such locations that will be kept wet by the surrounding brick, the wood plate used at the base of a column or wall is often borate treated wood commonly used for the protected sill plate of the remainder of the structure, likely because it is more readily available than copper treated wood products. Borate treated lumber is not intended for wet service, and this restriction is normally printed on the data tags stapled to the end of the sill plate lumber. If treated lumber is to be used at this location, it should be rated for frequent wetting, such as many of the ACQ treated lumber products, or better yet, the building should be properly constructed so that wetting of the framing is not likely to occur. This is normally detailed in the plans and ignored by many builders.
Topics: New Construction |