Drip Edge At the eaves and edges of every roof, a piece of metal drip edge guides water away from fascia boards and prevents it from creeping beneath underlayment.
Valley Flashing The point where roofs intersect should be protected with flashing that extends horizontally several inches up each slope, away from the point of intersection.
Step Flashing Where a sloped roof intersects with a vertical plane, such as the side of a house or a chimney wall, small pieces of step flashing provide the necessary water-proof transition.
Chimney Flashing Good chimney flashing is set in a groove etched into the mortar between rows of bricks. The metal actually penetrates the brick, forming a permanent watertight seal.

Siding Materials
Applied properly, siding serves the same function as roofing: It protects the home’s shell form the elements. Choose your siding early. Certain materials, most notably vinyl siding and synthetic stucco, have low permeability that requires the application of tight vapor barriers on interior walls. Here’s a list of the most common choices for exterior wall finish, along with some notes regarding important installation practices.
Wood Board Siding Galvanized or stainless steel ring-shank nails will hold wood siding to sheathing better than ordinary fasteners. Your builder can prevent splitting by pre-drilling all nail holes located near the ends of boards. At corners, lengths of siding should meet with tight mitered seams. Coating the end of each board with water repellant prior to nailing provides some added rot resistance.
Wood Shingles and Shakes One of the most traditional siding forms, wood shingles can be installed directly over sheathing or atop horizontal battens. In either case, look for level baselines and corners that are woven with alternating-edge overlaps. All corner seams need careful caulking.
Vinyl Siding This low maintenance siding offers another advantage—it is generally the lowest-cost material among all the options. The surface color runs through the full thickness of vinyl siding, so it stays looking like new throughout its service life. When installed over backer-board, vinyl siding looks crisp and is highly energy efficient.
Aluminum Shakes Panelized aluminum shake-look-alikes attach directly to sheathing or battens. Watch corners, intersections and flashing around doors and windows.
EIFS A multi-step stucco-like-coating, exterior insulation and finish systems provide an energy-efficient wall finish for new homes. To prevent damaging moisture infiltration, all windows and features must be flashed carefully. Some builders argue that EIFS should never be applied over oriented strand board (OSB) sheathing; instead, they recommend installing exterior-grade plywood.
Ventilation Factor Research has shown that a properly ventilated roof not only reduces a home’s energy bills, but also prolongs the life of shingles by reducing heat buildup in the attic. It also prevents damage from ice dams and reduces moisture accumulation under roof decking.
Poor roof venting can also affect siding. A roof with serious moisture problems often leaks into wall cavities, where moisture becomes trapped behind vinyl or EIFS siding; it can cause structural rot and render insulation ineffective. The simplest and perhaps the most effective roof ventilation system includes a continuous soffit vent (below the roof eaves), and a continuous ridge vent along the peak of the roof. But whichever approach you choose, make sure it’s adequate for the roof and exterior wall finish system you’ve chosen.