How To Layout Bottom of Stringer For Concrete

There is one thing you should understand, before you learn how to layout the bottom of the stair stringer for a concrete foundation or pad. If you can avoid it, try to prevent regular construction standard lumber from touching concrete, especially concrete that has the possibility of absorbing moisture.

This wouldn't include treated material, but keep in mind that treated material will rot and disintegrate over time, just like construction standard lumber, if it's in direct contract with moisture.

If you're looking for more information on how to layout the stair stringer, go back a few steps. The steps you're looking for can be found near the bottom of the page.

The illustration above provides us with a stair stringer layout, with all of the treads and risers marked. All that's left is to finish the bottom layout and the stringer will be ready to cut.

At this point, I'm assuming you already understand how to calculate and adjust the first step. If not, go back and revisit this page.

The stair stringer for our example, will be sitting on top of 2 x 4 treated lumber and it will need to be deducted, along with the thickness of the stair tread, from the bottom of the stringer, in order for the first riser, to be the same vertical height as the rest of the risers.

Don't make any mistakes on this calculation and don't forget to double check these measurements, after the stair stringers have been positioned properly, but before they are nailed off permanently.

For our example, we started with a 7 1/2 inch total rise and will need to deduct an inch and a half for the treated lumber and an additional inch or the stair tread.

This leaves us with a distance of 5 1/2 inches between the first step on the stair stringer and the bottom of the stair stringer.

You will need to adjust your stair stringer accordingly, if your measurements are different.

Here's what the stair stringer would look like if rotated into its proper position, but hadn't been cut yet. Illustrations like these often make it easier for some of us to visualize the process in our mind, before we cut our first board.

This is what the stair stringer would look like if it was sitting on top of a concrete pad or foundation, before attaching the treads and risers.

Sometimes a picture is worth a 1,000 words and if that is the case, then I can quit typing right now.

The photograph above provides you with an excellent example of a stair stringer cut out of Douglas fir or construction standard lumber, sitting directly on top of treated lumber that has been attached firmly to a concrete foundation.

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