Building stairs requires careful planning, the right tools and some installation know-how. Good rules of thumb are: When you add the height of a stair riser and tread width, the result should be to 17" to 18". Risers usually rise 7"to 7-3/4 and treads usually run 10". And once the stringers are installed they should sit at about a 35-degree angle. These measurements are somewhat adjustable, to make the stair assembly fit in an opening, for example.

Step 1

Take Measurements

Measure the height (called "rise") from the floor to the landing, where the top of the stairs will go (Image 1).

Divide the measurement by 7 or 7-1/2 to determine the number of risers the stringer needs. Round this to the closest whole number. Re-divide the total rise by this number (Image 2).

Step 2

Mark the Wood

With riser height determined and tread run known (10") fasten brass stair gauges to your framing square (Image 1).

Check your stringer stock. Make sure it is straight. If there is a crown, place the crown facing up (Image 2).

Place the square on the stringer stock. Apply pressure with your thumb to keep it flat and scribe the riser height (Image 3).

Without moving the square, mark the tread run. Keep gentle, even pressure on the square to keep it stable (Image 4).

Step the square down the stringer stock by placing it next to the previous mark. Repeat the process until all stairs are marked (Image 5).

Remove the stair gauges for the last mark so you can mark all the way across the board (Image 6).

Step 3

Cut the Wood

A circular saw (Image 1) is the ideal tool for cutting most of the stringer, however, do not over cut the stringer. Instead, use a hand saw to finish cuts. This ensures the stringer stock (usually 2x12) remains as strong as possible for heavy use.

Using a sharp handsaw to finish circular saw cuts ensures accuracy and ensures the stringer will be as sturdy as possible (Image 2).

Clamp the pattern piece to new stock and trace it (Image 3). This ensures accuracy between stringers, and speeds up the process.

Cut carefully. Make sure you always keep the saw blade on the same side of the line during every cut (Image 4).

When cutting the bottom riser, be sure to cut it one-tread-thickness shorter than all the other risers (Image 5).

Step 4

Attach the Stairs

At the location where the stairs will contact the landing, place riser stock (plywood) to create a connection point for the stringers (Image 1).

Place the stringers in place and on your layout marks. Fasten from behind the riser stock (Image 2).

Install riser material on the stringers. Cut each one exactly the same so the stair is the same width at all points (Image 3).

To really fasten the treads, glue and screw them down (Image 4). This prevents squeaks and makes a permanent bond.

Use screws, rather than nails, to fasten tread stock to the stringers (Image 5). Screws will form a tighter bond with the glue.

Sink screws from behind the riser stock into the edge of the tread (Image 6). This binds everything together into a unit.

Step 5

Attach the Rails

A sturdy rail is an important safety feature of any stair. It is vital that they are built properly and to local building code, to prevent accidents. The newel post should be set plumb and fastened with screws while the rails should follow the exact rise-angle of the stairs (Image 1).

After running the bottom rail along the stair nosings and fastening securely, use a block to transfer the measurement up to the next rail piece (Image 2).

Once you've marked where the next rail segment goes, fasten it to the newel post with screws (Image 3).

Run rail segments long and cut them off, once fastened in place, with a handsaw (Image 4). This saves you from having to calculate angles and lengths.

Step 6

Install the Handrail

Above the last rail, install a handrail. Install all handrail hardware the same distance from the last rail section to maintain the proper angle (Image 1).

Pre-miter and fasten the railing returns. Doing this prior to installation makes installation much easier. Pre-drill each side of the miter and set nails to fasten (Image 2).

Set the railing on the railing hardware and fasten from the bottom side (Image 3). It often helps to pre-drill holes to prevent splitting the wood.

Fastening all parts of the stair together with screws and installing a sturdy railing are the key to safe, sturdy stairs (Image 4).