Townhouses should be inspected the same way that single family homes are. I always quote the same price to inspect a townhouse as a single family home, because I inspect townhouses the same way; the roof, siding, windows... everything on the outside. Some people feel that these items don't need to be looked at because they're covered by the association, but these are well worth having inspected, regardless of whether they're covered or not.
The most obvious and logical reason for a buyer to have the common areas at a townhouse inspected is to know what they're buying. Buyers frequently think the common areas, such as the roof, don't need inspection on a townhouse because it's not their responsibility. What happens if the roof starts leaking and causes a big stain on the ceiling? The association will likely be responsible for repairing or replacing the roof, but who takes care of the water damage in the unit? Even if the owner doesn't end up spending a dime on the repairs, just the amount of time that could be spent dealing with these types of repairs would make it well worth their while to have the common areas on a townhouse inspected.
Another great reason to have the common areas inspected is that the association may not be aware of problems, and may not have repairs planned in their budget. If an association is budgeting to replace the roofs 10 years from now, but there's only two years left on the roofs, who pays for it? The owners, of course. These are what assessments are all about! I was once a member of an association where we had several assessments in one year, the largest of which was a $1200.00 assessment to replace the failing driveways. The extra money paid to have these items inspected is a wise investment.
If one of my customers specifically doesn't want the common areas inspected, I'll skip them and typically charge about 25% less for the inspection, but I strongly advise against this. In the long run, this fee is a drop in the bucket compared to the repair costs that just one failed component could cost. Below are some photos of a few costly repairs I've identified at townhouses just within the last year. As you look through these photos, just ask yourself if the association is aware of these issues, and has a budget to repair or replace these items. The answer is usually no.
Reuben Saltzman, Structure Tech Home Inspections