It’s what’s underneath that matters

Which is the best roofing product for a new home, steel roofing or asphalt/fiberglass shingles?

Actually, I dislike ’em both, especially during the winter thaw season. Why? Because they leak, and nothing in the home renovation biz is as frustrating as a leaky roof.

Therefore, if I had to consult a homeowner as to what type of product to choose in order to best protect their homes, year round, regardless of seasonal timeframe, I’d say cover your home with one of those vinyl roofed mega-domes.

So far, the only roofs that haven’t leaked at our lumber yard are the mega-domes. North, steel covered warehouse roof, leaks. Flat, rubberized roof over main store, leaks. Asphalt roof on main residence, leaks.

Very frustrating. So, for a mere $100,000, I say go mega-dome. If you’ve got two hundred grand to blow, I’d recommend doming the entire property, basically eliminating winter altogether.

If either scenario seems somewhat beyond budget, or practicality, and if changing the roof structure and general truss engineering of your home is equally as unlikely, then what can we do to make our roofs more dome-like?

Dome roofs have the advantage of being made of a tightly fitted, one piece, waterproof membrane. Unfortunately, roof dormers, chimneys, plumbing vents, skylights, or an attached garage, make the possibility of a one piece roof application in residential home construction, basically impossible.

That being the case, the best alternative is to follow some of the successful strategies of a dome type roof.

Step one, keep it tight. In our residential case, this means keep it solid. This can be achieved by ensuring your contractor uses minimally a 1/2 inch plywood, or 15/32 OSB (oriented strand board) roof-deck, as sheeting material over the trusses.

Bad things happen when roofing plywood sags due to the weight of a snow load. Steel roofing (being so thin) and asphalt shingles, have no structural strength.

As a result, the integrity of every seam between the sheets of tin, and the tar bond between shingle tabs, will be compromised should the plywood bend.

With “compromised” in the roofing biz meaning a leak is in the near future, we avoid the thinner (yet code compliant) plywood’s.

Note, in the past, steel roofing could be supported by 1×4 rough lumber. Because lumber is more unstable than plywood, causing screws to pop loose and mild warpage to occur, the better choice for steel roofing is a plywood underlay.

Next, we need an impermeable membrane. Roofing paper (again, code compliant) is a poor choice.

There are a number of quality synthetic membranes available, such as the Titanium UDL50 and UDL30 products, followed by the somewhat lesser weight, but still synthetic, Rhino and Deckgard products.

The better synthetic membranes are thicker, more tear resistant, and actually hug the nail (or screw) once it’s been perforated, providing optimum resistance to leaks.

What about installing an ice and water shield over the entire roof?

Ice and water shield is a heavy, rubberized peal and stick membrane that’s usually installed on the area of the roof that extends past the edge of the house. Ice and water’s main task is to guard against ice dams, so, installing it over the entire roof would certainly be overkill.

However, you could do it with a steel roof, but it would be aesthetically risky with asphalt shingles. The reason is the overlap, which with this thicker membrane, may cause a horizontal ripple in the shingles every 3 feet up the roof.

What about doubling up on the shingles, or installing steel roofing over existing asphalt shingles? This practice is no longer recommended.

Two reasons. One, its extra weight your roof trusses don’t need. And two, the spongy surface of an older shingle wouldn’t provide a good base for our new roofing. Best bet, remove the old shingles, assess the underlay, then remove or repair accordingly.

Good building

As published by the Standard-Freeholder
Handyman's Hints Standard-Freeholder Cornwall Ontario by Chris Emard

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