Pretty much every house I see with a basement has at least one support post helping to hold up a main beam.  This beam often runs the length of the house and it carries the loads from the floor joists.  These support posts hold up an awful lot of weight and so they need to be properly designed and installed.

Sometimes I see a type of support post that’s adjustable by telescoping in or out and then secured with a bolt (or two) in the middle of the post.  It looks like this.

But these posts have a very thin wall and they’re never designed or intended to be a primary permanent installation.  In addition to the thin wall of the post the top and bottom plates are very thin and deform easily, which causes the load to be concentrated over a very small area, and this can deform a wooden beam.  These posts are designed to be only temporary, or to be used only as additional or supplemental support.  If this type of telescoping post is being used as a primary post to support your main beam then you should replace it.

Let’s look at what the manufacturers of these posts have to say.  The Akron Products Company (akronproducts.com) is one big manufacturer of these products, and so is Tiger Brands (they both seem to be part of the same company).  They call their products that telescope in and out “floor jacks” and they’re described as being for “temporary support while making structural repairs” or for “temporary or additional support under stairs, porches, decks, crawl spaces and heavy load areas.”

By contrast, these manufacturers call their solid products “building columns” and describes them as “designed to be a permanent building column” and in compliance with the current building codes.  They look like this in the picture below.  These can be fixed length (on the left) or adjustable over a small range (on the right — adjustment screw at the bottom), typically about four inches.  They’re adjusted via a very large and robust screw threaded in at one end.  So keep in mind that just because a post is adjustable doesn’t mean that it can only be temporary or supplemental.  It’s the thin-walled telescoping type that’s only for temporary or supplemental use, just like the manufacturer says.

What are some situations where these temporary or supplemental floor jacks might be a good solution?  These days it’s pretty common when renovating a kitchen to open up the space and then install a kitchen island in the middle.  An island, including the cabinets and maybe a granite countertop, can be very heavy.  Some supplemental support under the island might be a good idea, and these telescoping floor jacks can be a good solution.  I’ve also seen them in old houses helping to support the stairs and landing down to the basement.  In that kind of situation they’re not carrying much load and would be a fine solution.

These floor jacks can be great for contractors.  Since they can adjust over such a wide length a contractor only needs to carry a couple of them and can still be sure to have one to fit the height he needs.  So they have their place in the home, just not a permanent place under the main beam of your house.

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