Stair stringers should always land on a level and well drained surface.
Attaching deck stairs to concrete pad.
If the stairs are resting on a concrete slab or a patio then the slab or patio should also be built with a similar foundation to resist frost movement.
As a bonus he details a rock solid method of attaching the bottom railing posts to the stairs.
This will be used to fasten the stairs to the concrete pad.
The fine homebuilding article stronger smarter deck stairs by steven baczek and mike brussard issue 258 april may 2016 offered a number of great suggestions.
Concrete slab or patio landings.
A concrete pad does not require the footings to rise above grade like other landing types.
Several building manufacturers make hangers that you can use to fasten stair stringers to concrete.
To cover the ends of the sleepers install deck fascia board.
These hangers are adjustable to fit most types of wood structured stairs.
Place the board between the stringers and attach to stringers with 3 galvanized deck screws.
However if you are landing on the yard you may want to install paver blocks or fill the area with compacted gravel to promote drainage.
When the lower floor is made of concrete you will need a special fastener to attach the wood to it unless one has already been embedded for this purpose.
Determine what type of landing you are going to have.
Each tread is made of two lengths of 2x6 board.
In order for a wooden stairway to be safe the stringers support boards should be securely fastened to both the upper and lower floors.
If you are landing on a concrete pad or a patio this should not be a problem.
The hangers are fitted to the back edge of the stringer and then bent to contour to the bottom edge.
Attaching deck stairs to footings.
A typical pad has a 4 inch layer of gravel underneath and about 4 inches of concrete on top.
When building a landing for deck stairs typical codes require the pad to extend beyond the steps about 36 inches behind the steps about 12 inches and on the sides of the steps about 6 inches.
Guertin also explains how he pours a concrete stair landing pad and how he attaches the bottom of the stairs to that.
If you attach the bottom end of your stringers directly to the concrete footing pad that long stretch of open wood grain will absorb water and rot even with.
One of the easiest ways to attach deck stair footings to concrete is through the base plate.
Attach the 2x6 board to concrete pad with masonry anchors.
If no concrete pier is used the post should bear on the footing and stringers should bear on 2x4 blocking fastened to 4x4 posts with 8x3 1 2 screws or 16d nails.
