OBSERVATIONS
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IN THIS ISSUE
Remember the old kids' joke: How do you make a pair of pants last? (The answer is the title of this article.) Making wood shingles last is, unfortunately, a bit more difficult. Some time ago we wrote a short article on culling and ripping shingles to eliminate the pieces most likely to fail before installing them (in Observations 15). We prefer to avoid using wood shingles when possible, because of their cost and tendency to fail prematurely. When wood shingles must be used, however, we recommend three steps to improve their longevity and to reduce the damage when they fail. We have not had long enough experience with them to be sure that they work without undesirable side effects, but initial reports are encouraging: Our first recommendation is to separate the shingles from contact with the roof decking, so that when their undersides get wet, they will be able to dry out readily. We have tried using battens nailed to the roof decking, and more recently, polymer matting. Battens get the shingles off the deck, but present problems. They can act as dams when water gets behind the shingles, creating puddles that then become centers of deterioration. Perhaps more seriously for an existing building, they raise the shingles about an inch off the deck, making it necessary either to taper them down to nothing at the gable ends of or to modify the rakes and shingle molds along those gables. Polymer matting is thinner and looks rather like a sheet of plastic pot scrubber. It appears to allow good drainage, but proper installation requires a drip flashing along the rakes, which may not be visually acceptable. The word on the street is that this is a good material that works well, but only time will tell for sure. The most common brand is Cedar Breather. The second measure that we recommend is to lay a waterproof layer over the roof deck itself, so that when the inevitable leaks occur, there will be less collateral damage. The traditional material used for this purpose is asphalt felt ("tar paper"); a more recently-developed product, which we prefer to use, especially on lower-sloping roofs, is the self-adhesive sheet typically marketed as ice and water flashing, whose advantage over asphalt felt is that it seals around nail penetrations. We have some concerns about the consequences of adhering this product to an old roof deck; in that situation, or where the roof deck is not in excellent condition, a 3/8"or 1/2" exterior plywood overlay makes sense. And finally, treating the shingles with a clear water-repellent before installation should slow their aging by reducing the amount of water they absorb (wood that has been treated will be much slower to weather and turn gray). Water-repellent treatments should be renewed every couple of years. There is little question that these measures will extend the life of a new wood shingle roof. The jury is still out, though, concerning whether they will do it over the long term without damaging the fabric of an irreplaceable old building. Back to the top Over the years, I've been involved in numerous grant applications, either as a preparer or as a consultant. I recently had a chance to see the other side of the process when I served on a panel evaluating preservation proposals for a granting agency in a near-by state. The panel consisted of four independent preservation practitioners, the director of a large municipal preservation commission, and a representative of a national preservation organization. Members of the agency's staff served as resources and facilitators. Projects ranged from assessments and historic structures reports priced in the lower tens of thousands to rehabilitations worth seven figures and more. The range of sophistication of the proposals was equally broad, ranging from thoroughly professional to well-intentioned but painfully naive. The panel met for a whole day to review the proposals and rank them for funding. The deliberations were spirited, focused, occasionally funny, and often enlightening. Some projects were easy to rate, for better or worse; the merits of others became occasions for hot debates. The panel worked together well; strong opinions were expressed, but decisions were typically made by consensus. Now that I have seen the grant process from the other side, I have some thoughts to offer organizations and individuals contemplating applying for a grant: First, in preparing your application, put yourself in the shoes of the evaluators! Make their job as easy as you can. The material in your submittal will be all that they have to tell them about your project and why it deserves funding. Make sure you give them what they need for a favorable decision. Some submittals I saw lacked basic material necessary for the panel to understand them. One application failed even to tell the specific purpose for which the grant funding was requested. It was unfortunately typical for buildings to be described as "important" parts of larger streetscapes or landscapes, but for evidence of that status--photographs showing them in their context, maps, and the like--to be nowhere to be found (and the granting agency did request context photographs in its instructions to applicants). On the other hand, an application can be too complete. One application measured almost three inches thick. It was a very serious and professionally-prepared contender, but three inches was still a bit much to wade through. I was relieved that it was not one of the applications that I had to study beforehand and be prepared to recommend on! A second important point is that if your proposal is not funded, by all means ask the granter why! Most granting agencies want proposals to be as strong as possible. They are often willing to spend significant time reviewing the strengths and weaknesses of an unsuccessful application. This agency was no exception. But then, if you have a chance to re-apply in the future, use what you have learned. It was bamfazzling to realize that some of the weakest proposals we saw were unrevised rehashes of unsuccessful submittals from a previous grant round. In almost every case, the proposers had discussed their proposals with agency staffers, but had failed to make any changes before trying again. So, when you next submit a grant application, make it complete and compelling. Whether or not it gets funded, the evaluators will thank you! Back to the top Condensation on windowpanes can be used as a rough-and-ready indicator of unsafe environmental conditions: If it's humid enough inside the building to fog up the windows, it's probably humid enough to be causing condensation inside the wall cavity, too (unless the house has a good vapor retarder, which old houses rarely do). Air plus moisture plus wood plus dark equals potential decay at temperatures above about 50¡F. It also equals an inviting environment for wood-destroying insects--termites, carpenter ants, and beetles. It's difficult in New England's climate to prevent some condensation from occurring. In the fall, temperatures fluctuate widely between day and night, and the building is shedding the moisture that it absorbed during warmer weather. This is a problem even in a museum house that is not lived in--and so is not exposed to the humidity generated by cooking and bathing--and does not have to be heated for comfortable occupancy. As fall gives way to winter, the focus shifts to the tension between providing enough heat and moisture in the indoor air for occupant comfort and not raising the amount of airborne water vapor to the point where condensation will occur inside the wall cavity, where it can foster decay. A little condensation on the windows the first thing in the morning when you open the shades is probably not a cause for alarm, but frosted-over windows, or windows that don't clear by mid-morning usually indicate a problem. Given that some condensation is going to occur, whether it forms on the primary or the storm glazing of a single-glazed window provides a check on air leakage: All other things being equal, it is desirable for the primary (inside) window to form a tighter seal than the secondary (outside); it encourages the water and vapor that inevitably enter the space between the two sash to escape to the outdoors. In a well-regulated world, when moisture condenses on windows in cold weather, it should only appear on the inner glass. Condensation forming only on the outer glass is commonly an indicator that the inner sash is not tight enough to prevent warm, moisture-laden air from getting into the space, where it is chilled and condenses onto the outer panes. Back to the top Copyright 1991-2008 Allen C. Hill |
