The Home Inspection Professionals in Binghamton, New York

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Inspecting Cathedral Ceilings

by Gregg Harwood

Over the last forty years cathedral ceilings have become increasingly more popular in home design, giving an open, spacious feel to many rooms. However, from a home inspector's viewpoint, they present an interesting problem. Each cathedral ceiling is like a "mini-attic", with all the systems that a full attic has, but none of it is visible. How do we inspect it?

First I would suggest that you inform your client, verbally and in your report, that due to the inherent lack of access, the systems within a cathedral ceiling can not be fully inspected. However once that is done there is quite a bit that we can learn from observation. I feel that the two most important questions that we can attempt to answer are; "What holds it up?" and "How is it ventilated?". A major defect in either of these areas can lead to structural failure and substantial repair costs.

"What holds it up?"

Most successful cathedral ceiling systems are framed in one of three basic ways; rafters with ties, rafters with structural support at the peak or scissors trusses. Rafters with rafter ties are just a modification of conventional gable roof framing which relies on the bottom chord to hold the base of the rafters in and prevents the side walls from bowing. The lower the ties are installed on the rafters the better they will perform. Generally, there will only be a few ties installed to maintain the open feel of the ceiling. Therefore, each tie must do proportionately more than an individual ceiling joist in a standard gable frame. Look for any signs of movement, such as separation where the ties attach to the rafters, bowing of the sidewalls or deflection in the ridge.

Rafters with structural support at the peak do not need rafter ties to keep them from spreading. In these roofs, each end of the rafter rests on something solid, either a partition or a beam. It is important in this type of roof to trace the bearing walls or posts to make sure that they are adequately supported from the footers to the peak. Be suspicious if bearing members do not line up vertically.

Scissors trusses, like other trusses, do not need mid-span support and can clear span from exterior wall to exterior wall. There will usually be a three feet or more difference in the height of the ceiling peak as compared to the roof ridge if you are dealing with scissors trusses. This is due to the differing pitches of the roof and the ceiling. This is readily visible in skylight chases.

"How is it ventilated?"

Adequate ventilation is very important in a cathedral system, just as it is in a standard attic. However we do not have the opportunity to visually inspect for stains and decay in the enclosed portions of a cathedral system. Any stains found on the finished surfaces or warpage of roof sheathing should be identified and further investigated.

It takes a certain amount of space to fit in a ventilation system and adequate insulation into a cathedral ceiling. For example, in our area of the North East where R-30 ceilings are the norm for modern construction, any system with less than the equivalent of a 2X12 rafter depth has to be viewed with suspicion. If the builder used fiberglass insulation, it takes 9 inch batts to give us the R-30 that we need. We can see that a 2X10 rafter, which actually measures 91/4 inches, will not have adequate depth to provide a ventilation space.

Of course, one of the main reasons for having ventilation in a roof system is to remove moisture so that excess condensation does not form on cold framing components. In a standard gable attic there is a large amount of open air space between the finished ceiling and the roof sheathing. It is possible to have adequate ventilation in this type of system with widely spaced soffit and roof vents because some circulation and mixing will occur in the open air area. However, in a cathedral type system, each rafter bay must be viewed as a separate space to be vented. Any moisture that migrates through the ceiling is immediately in contact with the rafters and sheathing. By far, the best system is one that uses continuous ridge and soffit vents to vent each rafter bay. Of course, some cathedral ceilings were never intended to have ventilation. These are the ones with no sealed cavities, where the exposed ceiling boards double as the roof sheathing or the systems that employ rigid foam insulation.

A horror story.

A few years ago I was asked to testify in a case involving the issues discussed above. A couple had bought a ten year old contemporary style house and the next winter noticed that water was dripping from the recessed lights in the living room cathedral ceiling. Further investigation revealed the following conditions. 1). The finished ceiling was 1x6 boards applied directly to the rafters with no drywall or other vapor barrier. 2). The insulation completely filled the 2x10 rafter bays. 3). There was no ventilation system in place. Sheathing and insulation were wet. 4). The peak of the roof was held by a combination of bearing walls and posts which were adequate on the first and second floors, however, the builder had never completed his work in the crawlspace. The entire interior of the structure was held up by a few temporary 2x4 posts set on blocks of kiln dried lumber. The crawlspace was wet with no plastic ground sheet and there was some decay and broken wooden beams.

The home inspector had not entered the crawlspace. His report had not addressed any of these issues. He was found liable for the entire cost of repairs to the tune of twenty four thousand dollars. His defense was that there was snow on the roof at the time of inspection so he couldn't see the lack of vents. Of course, he did not say this in his report. This gentleman would have been better of if he had answered the two cathedral ceiling questions. "What holds it up" and "How is it ventilated".