Tuesday, June 30, 2009

Up on the Roof . 1

Few improvements both enhance the enjoyment of your home and increase the value of your house as much as a good roof deck. Relatively inexpensively you gain a whole new room - an outside room, possibly with a spectacular view across the city and a space as large as the footprint of your house.

Every rooftop presents unique opportunities and challenges. We're going to start with the simplest, quite common existing situation, which will result in the easiest, least expensive project to build. We're looking for a fairly flat rubber covered roof, one with only a slight pitch, surrounded by a parapet or other walls with a roof house or hatch for access from indoors.

Virtually all modern flat roofs are now covered with rubber and all the old time tar and gravel roofs are being replaced with rubber when their time is up. The steaming, roaring tar cauldron by the curb is now mostly extinct. The rubber, resembling that of a bicycle inner tube but thicker and stiffer, is installed over thick foam insulation board fastened to the roof and comes in very wide rolls and specially shaped fittings all bonded together with some nasty sticky stuff.

Obviously, the roof surface, and all the through the roof rubber fittings and metal flashings should be in good shape before installing a permanent deck. Certainly there should be no roof leaks of any sort in the house. If you have any doubt, hire a reputable roofer to look over the situation, spot problems, if any, and suggest solutions. I'll give you the name and number of my roofer to call if you're in the Boston area: Mike Duby at Ideal Skylight and Roofing at 508-583-8558. He's truly an 'old pro' and we've worked together for many years.

The structure of the roof should be sufficient to bear the deck itself. If there are any doubts about that - you're already in trouble because a deck weighs next to nothing compared to the huge dead load imposed by a good snow storm. If there's any doubt at all - or you're planning to plant a forest of numerous, heavy planters, hire an engineer or architect to evaluate the situation and advise you.

The second thing we're looking for, the parapet or walls surrounding the rooftop is to keep things simple, so that we don't have to get into building walls - which we'll go into in future articles.

The third criteria is access to the roof itself up a flight of stairs tthrough a roof house or a ship's ladder to a hatch. Access up a fire escape is far too dangerous and probably illegal wherever you live. If you lack roof access, it can often be created, but that's definately a story for another time and probably a project for a pro.

Is it possible to use the roof without a deck, just walking right on the rubber? Not a good idea. Debris could be pushed down under foot and puncture the surface causing leaks, the insulation board would become crushed and lose its thermal properties and rubber roofs are hazardously slippery with any sort of moisture present. To use any sort of roof you need a deck.

Flat roofs, so called, in fact all have at least a slight pitch to shed water. Standing water is never good on a roof. But it doesn't take much of a pitch to make water run, maybe only a degree or two. Most flat roofs tend to pitch towards the back of the building and drain into a gutter. Under the roof the rafters which support it usually run at right anglees to this slope, spanning between the side walls of the house. The deck we are going to build, therefor, will rest on wood sleepers over resilient rubber padding, much like railroad ties, which run down the slope of the roof to allow it to drain and also spread the load across the roof rafters. The deck boards will then be laid and fastened at a right angle across the sleepers.

Image ... Don Bailey reading out on his roof deck. Beacon Hill, Boston.