How to Line Up Deck Stringers

Align one of the stringers with the edge of the decking, making sure that the top of the stringer is level with the top of the deck surface. Rest a builder's level along one of the tread cuts in the stringer and adjust the stringer position until the tread is horizontal and parallel to the deck top.

Attach the first stringer to the deck framework using the method recommended by the deck manufacturer or specified in your own designs. This may be achieved by attaching it to a joist holder or by bolting or screwing it to the deck framework.

Check the position of the stringer while you attach it, and make any fine alterations to the positioning. Once the treads are horizontal and the stringer hangs precisely vertically, tighten all the fastenings to their maximum extent.

Offer the second stringer up to the deck on the opposite side of the stairs. Position it by eye, attempting to match the level of the treads with those of the first stringer. Attach it loosely to the deck framework using the same technique you used in step 2.

Measure the distance between the inner edges of the stringers at the top where they join the decking. Use this measurement to check, and adjust if necessary, the distance between the bottoms of the stringers. When finished, the distance between the stringers should be identical at the top and at the bottom.

Rest a builder's level between the stringers, spanning the gap between the tread slots on both sides of the stairs. Adjust the height of the second stringer until the builder's level indicates that the tread slots on both stringers are perfectly level.

Fasten the second stringer in place securely. Check the width and level repeatedly as you secure the stringer, making any fine adjustments as required to keep the stringers correctly positioned.