Apply the building paper or felt sheathing protection that is recommended for your area.
Apply roofing felt (tar paper) or building paper that is recommended for your area. Many builders use standard 15-pound roofing felt. Felt labeled "ASTM 15" meets specific standards and is the norm in many areas. It protects the sheathing against moisture infiltration yet allows some air passage so the wall can breathe.
Building paper, also called house wrap, is a strong, fibrous paper that blocks water and moisture from entering from the outside but allows moist air to pass through from the inside, preventing a buildup of moisture inside walls that can lead to mold.
Felt or building paper must be applied to walls properly to be effective. Install pieces in the correct order and make cuts carefully, so any moisture can travel downward at all points without slipping under the wrap. Install flashings (metal, self-adhesive, or both) as recommended by the window or door manufacturer or as required by local codes. Pull the wrap tight when you install it to prevent creases that could lead to slight waves in the siding.
Working with one or two helpers, half a day to apply 1,600 square feet or so of building wrap; more time if extensive flashings are required
Hammer stapler, utility knife, hammer, chalkline, ladders and/or scaffolding
Remove any old siding, nails, and building wrap from the sheathing.
Building paper or felt (tar paper), cap nails and/or staples, sealing tape, metal and self-stick flashings as needed
Working with a helper, install the bottom piece of felt so it extends 1 or 2 inches below the sill plate. Roll out a length of 8 feet or so; check that it is level and aligned with the bottom of the house. Use a hammer stapler to tack it in place. At an inside corner, use a straight board to hold the felt tight to the corner as you staple.
If you will be attaching the building paper with cap nails, use a chalkline to mark the sheathing with the locations of studs. Working with a helper, unroll the paper so it is about 2 inches below the sill plate and pull it taut. Check that it is level and aligned and drive staples or cap nails.
Install succeeding courses of paper so they overlap the course below by about 6 inches. If you need to make a vertical joint, overlap the pieces by 12 inches. Use recommended contractor tape to seal all the seams as well as any tears in the paper. Tape around windows and doors as well.
If you have a rough opening where a new window or door will be installed, run the paper over the opening and secure it. Make two horizontal cuts along the opening at the top and bottom. Near the center of the opening, make a vertical cut running from the top to the bottom cut.
Cut a piece of self-stick flashing 12 inches longer than the bottom opening. Remove the bottom release sheet and apply it so it wraps up 6 inches onto the side sills. Drive two cap nails at each corner to keep the flashing in place where it has stretched.
If the window is installed after the siding, follow manufacturer's instructions; you may install drip-cap flashing over the top trim piece. If the window will be installed before the siding, set it into the opening and attach self-stick flashing pieces on the sides, then the top. Fold the upper flashing down; first install a drip-cap metal flashing if that is required.