The exterior protects the house from the elements. An important part of the exterior inspection is the roof.

What type of exterior siding does the house have? Is it wood clapboards, wood shingles, vinyl siding, aluminum siding, textured-111 plywood, board-and-batten, vertical tongue-and-groove, log veneer, novelty siding, log, or brick masonry? The purpose of all of these siding materials is to shed water and prevent wind and water infiltration.

On all wood exteriors, the most important thing to check for is rot. Sometimes, you can see the rot from a distance. It pays to get up close and examine all siding areas where moisture can build up such as adjacent to steps and landings, roof surfaces, and exterior plantings. Be particularly vigilant while inspecting newly painted exteriors. You can "hear" rotten areas by gently rapping the siding surface with your knuckle or "feel" rot by applying gentle force with a thumb. Sometimes I use the handle of a screw driver. It is not unusual for sheathing and sill rot to develop behind clapboards. You will not be able to see this. However, by resting your elbow gently on the exterior and thumping the surface lightly with your fist, you will sometimes notice a bounce in the exterior that might indicate rot behind the siding that should be investigated further.

By the way, unless you have made prior arrangements with the owner and are paying an additional inspection fee, do not expect your home inspector to remove exterior siding in order to find hidden rot behind it. Home inspectors are very careful not to damage the property they are inspecting. That is why they frequently recommend further investigation if they suspect hidden rot.

Clapboards and wood shingles have been used for a long time on wood-framed residences. If you are looking at a home that is more than 100 years old, it might have the original radially sawn clapboards. You can spot these easily because most of them are about four feet long or shorter. These clapboards were sawn out of a wood dowel so the grain would be distributed uniformly from the butt to the feather edge. Clapboards sawn this way resist splitting and cracking and can last 200 years or more. They resist splitting because, for most wood species, expansion and contraction as a functioin of moisture content is considerably less along the radius of the tree than around the circumference. The dense exposed edge grain on radially sawn clapboards also seems to hold paint and stain better.

As a rule, today's clapboards are sawn with a random grain orientation although I have seen many cedar clapboards that appear to be sawn radially. Because some newer nonradially sawn clapboards can buckle, warp, and split, it is necessary to pay particular attention to clapboard condition particularly at sill level, adjacent to roof surfaces, on the south side, or where replacements have been installed on older houses. Cyclic expansion, contraction, and buckling can withdraw clapboard nails and open up gaps between adjacent clapboard courses.

The next most common siding I find in the coastal Maine area is wood shingles. Cedar shingles have been popular for a long time because they could be left unpainted. Today, red cedar seems to have the best life expectancy but more commonly you find various grades of white cedar being used.

Here are some tips on inspecting cedar shingle siding. What is the exposure, that is, how much of the shingle is exposed on each course? What is the grade or quality of shingle? In other words, how many knots are visible? Pay particular attention to the south side. Sun and rain have a way of eating away at wood shingles. Eventually, this weathering erodes the exposed shingle wood away until it becomes quite thin. As you would for any siding, check for rot around sill areas, adjacent to steps and roof surfaces, and at any spot where there might be or might have been high moisture. If you are looking at a home or cottage near salt water, try gently lifting out on several of the wood shingles. What you are trying to find out is whether or not the nail fasteners have rusted out. Near saltwater, shingle nail fasteners can rust completely away long before the clapboards wear out. If the nails have rusted out, shingles will get so loose that they can be removed without pulling the nails.

Vinyl and aluminum siding are often installed over older siding. The main advantage of this is reduced maintenance. In order to get a uniform exterior appearance or color, wood siding has to be painted every two to five years. Aluminum or vinyl siding can be painted but does not have to be. Another advantage depends on the quality of the installation but can pay off at sites exposed to extreme weather conditions. For example, I have seen vinyl siding installed over old siding on cottages on bold oceanfront and, apparently for the first time, the cottage sidewalls don't leak during winter storms.

Here are one or two disadvantages to vinyl or aluminum siding. If a lawnmower, grass whip, snow shovel, or snow plow damages vinyl siding, it is necessary to replace a whole section or find some way to patch the hole, crack, or dent. Because the siding sections interlock, it can require special skill to replace sections. If a matching section can be found, the color might not match due to fading. Where vinyl siding meets with a roof surface, it can be more time-consuming to repair and replace flashing later on during roof surfacing replacement.

Textured-111 plywood siding is often installed as both sheathing and siding. After twenty or thirty years, plywood siding has a tendency to weather and delaminate on the side facing south. On one house built in the 60s, I found that previous owners had installed cedar shingle siding over the textured-111 plywood siding on the east and south sides.

Board-and-batten siding is also usually installed as both sheathing and siding. Typically, relatively low grade boards are used so that, after a few years, knots get loose and fall out. Warpage and curling of wide boards commonly used tends to withdraw the nail fasteners securing the battens. This undovers the gaps between the wide boards. If you can see through knot holes and gaps into the wall cavity, then the exterior is not weathertight. While this can be a relatively inexpensive way to sheath a house, it does not last forever.

Log veneer and novelty siding are also materials that appear as if they were originally intended to function as both siding and sheathing. The grooved overlapping horizontal boards can be installed to be reasonably weathertight.

In Maine, there are quite a few "log cabins". On a true log house, the logs function as exterior siding, sheathing, insulation, and interior finish. Modern log cabin designs utilize interlocking tongue-and-groove joints. Cedar is the best wood for log cabins. Since they are somewhat naturally decay-resistant, cedar logs endure better than pine logs. I have seen pine logs deeply checked both inside and outside. On one pine log exterior I inspected recently, the logs were so deeply checked that rot had developed around the checking to a depth of as much as two inches. On older log cabins, you will find the logs coated with a dark preservative similar to creosote. Window and door openings require special treatment on log houses. Modern log cabins rely heavily on flexible caulk applied to the interlocking seams during construction. Occasionally, I will find a log house with all of the log seams caulked inside and outside. Oakum is still found in the log seams of older log cottages. If you are looking at an older log house, pay particular attention to the exposed log ends at corners, around window and door openings, and under the roof overhang. Your home inspector should check for wood boring insect infestation in log cabins. I look for softened wood, holes in the log surface, and accumulations of wood shavings. If you listen while rapping on the log exterior with a screwdriver handle, you can tell by the sound if the log is solid, soft, or hollow. It requires special skills to replace rotten logs in log buildings.

Brick masonry provides a durable, long-lived exterior. Check for cracking and structural shifting as a result of uneven foundation settlement. Brick buildings are heavier than wood-framed buildings so there is quite a bit more weight on foundation walls. It is not unusual to find step cracks in mortar joints near corners of window and door openings. Check the condition of wood window and door lintels. I have found parts of recessed window and door trim completely rotted out. The rot tends to occur under porches or in other shaded areas where moisture accumulates.

If the house has cathedral ceilings, your home inspector should check for bulging eaves and sagging ridge.