Told you so …

Harris welcomes Hoard’s support

by Martin Harris
August 1983

When you’re looking for “I-told-you-so” ammunition, you grab for it anywhere you can; so it was very pleasant, if rather unexpected, for this correspondent to find unexpected support for his arguments in favor of steeper roof pitches within the pages of Hoard’s Dairyman.

A writer in a recent issue of that publication observed that ventilation in open-ridge free-stall buildings is enhanced as roof pitches grow steeper. As one can easily visualize, stale air is more likely to flow sluggishly, if at all, under roofs of slight pitch. Speaking of a South Carolina dairy housing set-up, the anonymous author of the article quotes the farm’s owner, veterinarian Doctor Boys Parr: “the roof creates its own breeze.”

The pitch of that roof isn’t much by traditional New England standards (a mere 4:12, far less than the 10:12 that was standard throughout most of the 19th Century or the 12:12 that was briefly popular around the turn of the 20th Century) but it’s substantially more, percentagewise; than the 2:12 and 3:12 pitches being seen all too frequently today.

Modern builders like to scoff at the old steep pitches, and perhaps they are a bit more than what is really needed in this climate of ours. But not much more. In this correspondent’s judgment, based on some 20-plus years of looking at a variety of roof problems, the dividing line is about at the 6:12 pitch. Steeper than that, and problems with structure, ice damming, glaciation, and even leaks seem to be minimal. Flatter than that, and all those troublesome symptoms emerge.

Modern builders have two very substantial reasons for wanting to avoid the steeper pitches, even the less extreme 6: 12 design, and both are based, not on life-cycle costing for the building, but rather on initial construction cost only.

The arguments

First is materials cost. Clearly, a flat roof needs no more material for constuction than the building’s footprint on the ground. If the structure is, say, 5O feet wide, the roof is likewise 50 feet wide. At a 2:12 pitch the roof “run” is now 50.68 feet, an increase of about one percent. At a 4: 12 pitch the increase is about five percent; at 6:12, it is not quite 12 per cent. For the old-style 10:12 pitch, it is a full 30 per cent. The real cost of a steeper pitch, in terms of materials, is the percentage difference between a lower and higher choice: For example, a design employing a 6:12 in lieu of a 2:12 roof design entails an 11 per cent gain in roof materials costt.

A second argument is based on labor costs, and derives from the fact that roofing crews can safely walk on 2: and 3:12 slopes, cannot do so when the pitch increases to 6:12: The extra inconvenience and staging required, builders argue, adds to construction cost.

What arguments can one muster to counter the above points? Why is it worthwhile to spend the extra money for the steeper pitch? It’s not easy to rebut the extra-cost argument: One can’t claim for example, that lower pitches must be engineered more expensively than steeper ones because of snow-retention, for standard roof engineering procedures don’t recognize any difference. A required snow-and-wind load capability in, say, a 40 pound geographical area, is the same , whether the roof is shallow or steep in pitch. (Whether that official position is logical and sound has been explored in a previous column.)

One must, instead, fall back on less easily documented arguments. In fact, there is basically but one argument: Experience. Experience with ice-dams when snow and ice don’t move off the eaves and back up melt-water behind them. Experience with glaciation when snow and ice move over the edge very slowly, building up to projections of several feet and several hundred pounds before they break and fall with potentially dangerous consequences. Experience with the structural damage that occurs when snow and ice grab hold of the roof material and drag it off the building. Experience with occasional unusual snow loads that won’t slide off and must be shoveled off.

Bottom line

Unfortunately, these sorts of experience don’t often stand up against the first-cost argument with its obvious dollar implications. An owner who has not directly experienced any of the difficulties described above is not going to be easy to convince to spend the extra money for a somewhat steeper pitch. After all, for 10 or more months of the year one can’t even point out the sorts of problems that might arise in the depths of Winter; but the bottom line of a construction budget is always visible.

And so, one is reduced to a feeble sounding set of observations, not found in any text or design manual, to try to argue that a steeper pitch is, in fact, a good buy for very practical reasons. Of course, no one likes to hear “I told you so” after the fact. Nor does it do any good for the owner who chose not to listen before the fact. Nor, seemingly, does it impress the next owner about to make the same sort of decision. So, that’s why it’s nice to have support for the argument emerge from an unexpected quarter, even if the argument isn’t relevant to the vast majority of buildings which aren’t open-ridge dairy housing facilities.

After all, when you’re looking for ammunition, you take it anyway you can get it.