How to Square a Partition Wall

Select an existin wall as your reference point and take all measurements from there. Starting at the wall, measure along the room to the point at which the bottom plate of the partition wall will be installed. Mark the floor at these points. When finished there will be a mark on each side of the room, representing the position of the bottom plate.

Attach one end of a chalk line to one of the marks -- using a tack nail or self-adhesive putty -- and stretch the chalk line across the room to the opposite mark. Pull the line taut, lift it between your finger and thumb, then allow it to snap back into place. The result is a chalk line imprinted on the floor, forming a straight line across the room.

Measure the distances determined in Step 1, starting at the wall and moving along the ceiling in the direction of the bottom plate. Mark the ceiling at the appropriate distances. The result is two marks on the ceiling directly above the two ends of the bottom plate.

Hold a plumb line against the ceiling above the chalk line. Carefully adjust its position until it hangs directly over the line. Mark the position of the top of the plumb line on the ceiling. Repeat three or four times across the width of the room, taking care to align the plumb line directly over the floor line every time.

Attach the bottom plate to the floor as instructed by the builder's plans and any relevant building codes. Ensure that it is situated directly along the chalk line.

Attach the top plate to the ceiling, using the marks as a guide line. Use only one attachment point at each side of the room. Check the position of the top plate. Hold the plumb line against the side of the top plate and observe the position of the plumb bob hanging directly below it. The top and bottom plates are square if the plumb bob hangs directly over the edge of the bottom plate when the top of the line is held against the corresponding edge of the top plate.