I recently got a note from the new owners of a townhouse in the Baltimore area. The house was built in the early 1950s with a slate roof.

Before settlement, they said they had a home inspector check the roof and no problems were found. However, after living in the home for a week the new owners discovered a significant leak in the roof. They got an estimate from a slate roof company and learned it would cost about $5,000 to repair.

The owners' question was who's responsible, the home inspector for missing the problem or the seller for not disclosing the problem.

My suggestion is to call your home inspector and explain what has occurred since you took possession of the property. Most home inspectors would want to return to the property to re-evaluate the roof under these circumstances. If the inspector does not offer to return, request that he do so in order to help you understand why a serious problem that was not found during the inspection has come to light so quickly.

A problem may have been latent and undiscoverable, for instance, like a water heater on the brink of rust-through. Or a defect may have been manifest, but difficult or impossible to discover during an inspection. This can occur where the evidence of the problem was concealed in a space which was, for all practical purposes, inaccessible to the inspector, or where the evidence of the defect had been covered up or eliminated by a zealous or unscrupulous seller during preparations for sale of the house.

Often, a little investigation when the inspector returns to the property reveals that the problem is not what it appears, and fears can be quickly laid to rest or a simple solution can be found that is painless for everyone. In some cases, it becomes apparent that an aggressive salesman or contractor has overstated or misrepresented a problem to generate work, or has a particularly conservative - and expensive - approach to repair and maintenance.

In my experience, old valley flashings on slate roofs are a likely area for widely varying approaches by different contractors. Many a roofer, even good ones, will nurse along a valley that has become thin from the gradual corrosion caused by acid rain, leaves and abrasion. Even after pinholes have begun to develop, they will be sealed or the flashing will be coated to prevent leakage and forestall replacement of the flashing. This can easily go on for a decade.

The high cost of re-flashing is the reason for this, and it can be very cost-effective for the homeowner to take this approach. But the same roofer may, when first looking at a slate roof for a new owner, recommend immediate replacement of all the worn valley flashings, even where there has never been a leak and there are no patches in any of the valleys.

In such a case, the home inspector who advised the new owner should have advised that the flashings were old and nearing the end of their reliable life, but should not be faulted for not calling for their immediate replacement.