“Why do you home inspectors always pick on those jacks?”
“This house needs those posts with screw thingys at the top because it settles every year. How can I adjust the floor without them?”
“I installed them for additional support.”
“Why do they make them if I’m not supposed to use them?”
And one of my favorite explanations from contractors: “I’ve always used ‘em and have never had a problem.”
What exactly is a “telescopic adjustable column” or a “split type” adjustable post? It is hollow steel tubing which comes in two or more sections that slide inside each other and are assembled on the job site. These tubes have holes drilled in them and a pin is used to set the starting length of the assembly. Inside the top of the smallest diameter tube is a threaded insert which acts as a nut. This nut works in conjunction with a threaded rod to allow for small adjustments in length. These types of columns are not intended for permanent installation. Yes, they are often found being used as permanent structural support, but unless they have been analyzed by a licensed engineer or have been specifically listed as suitable for permanent support, they should only be used for temporary support.
As a home inspector, my job is to inform my client about conditions which could have a significant adverse effect on the value of property, significantly impair the health or safety of future occupants of the property, or if not repaired, removed or replaced, significantly shorten the expected normal life of the premises. An improperly installed support has the potential to kick out at the top or bottom, which could cause injury to anyone in the immediate vicinity. An undersized support could fail and result in the beam or joist it is supporting to fail, possibly causing injury and could be costly to repair. Depending upon the loading conditions, the failure of a load bearing column could shorten the expected life of the structure through a multi-story failure.
Back to the question of: “Why do you inspectors always pick on those jacks”?
First and foremost, these telescoping columns are not intended for permanent installation. Also, not all home owners and contractors understand the implications of improper selection and installation of columns. All too often these adjustable supports are used and installed improperly. They are not intended to be used for the initial lifting (jacking) of the structure. A hydraulic jack or screw jack should be used to elevate the structure, then the adjustable steel column is inserted. Once in place, it can be used to make small adjustments in elevation with the screw jack portion. Plates of proper material and thickness are required at the top and bottom of each steel column so as to prevent the cylindrical ends of the columns from punching through a wood beam or joist at the top, or into the floor at the bottom. The load rating of an adjustable column is based it being installed plumb (i.e., perfectly vertical). If the column is even slightly out of plumb, there is serious risk of injury or death as weight from above can force the post to kick out, either from the bottom or the top. Another item to consider is the elevation of the threaded portion should be reduced as much as possible because this adversely affects the support’s strength.
As an engineer, when I see a support column I ask myself if the column is capable of transferring the load from the structure above to the soil below. Of course, in order to answer this question many more questions must be answered: what is the actual load being transferred to the column, what is the material of the column, is there a footer installed, how thick is the footer, what is the bearing capacity of the material below the footer, and what is used to prevent kick-out at the top and bottom, to name a few. While performing load calculations may be fun, a home inspector does not, and should not, delve into this area.
As a home inspector, when I see a support column an “if-then” scenario comes to mind. To make the evaluation process easier, I created a flow chart which leads the user through some simple questions and ends with what to write on the home inspection report.
While not intended for permanent installation, adjustable supports are an important tool. They are used during construction while the support called for by the structural engineer is being installed. While renovating or remodeling a building, they are used when a load-bearing wall is being replaced with a beam. They are also used to temporarily support beams and headers when columns and walls need to be repaired or if a sagging or damaged joist requires the installation of a permanent support.
One just needs to remember that unless the column is of the correct type and is properly installed, it should be used for temporary installation only.