How Do I Fasten The Lower Section of The Stairway To A Concrete Foundation?

The picture above shows two 4 x 12 stair stringers sitting on top of a concrete pad, with an L bracket attached to each one on the inside. This is an excellent way to attach the bottom of larger stair stringers like these, to a concrete foundation.

Here's a closer look at the L bracket. There are two lag bolts going into the stair stringer and two going into the concrete foundation.

The lag bolts should be pre-drilled, otherwise larger lag screws like these can and often do crack the stair stringer. The two screws or bolts going into the concrete, would require some type of anchoring system, like lead or plastic sleeves, along with a predrilled hole in the concrete.

You could also use some type of anchor bolt epoxy system, but the most difficult part of this process, will be to drill the holes in the concrete. This usually requires a hammer drill and the exact sized drill bit, to match either the epoxy system you're going to use or the lead anchors.

This is the most common way to attach conventional framed stairways to a building foundation. Stair stringers will sit directly on top of treated lumber base plates and will be fastened securely with some type of shot and pin anchoring tool.

Here is a close-up of the stair stringer sitting on top of three pieces of treated 2 x 4. Some stairways will only require two pieces, while others might require four.

If you're not sure how many boards you need under the bottom of your stair stringer, then take the more is better attitude. Four it is always going to be better than three and three is always going to be better than two.

The arrows in the picture above or pointing to the pins that are driven with a specialized tool into the concrete foundation.

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