Homeowners can choose between several different flat roof designs, and all of
them cost approximately the same, but prices can vary according to region and roof size.
Creating a home extension results in a structure like a shed that fits
right up next to an existing building, leaving no space for a pitched roof.
This creates the potential for condensation due to the gaps in
temperature; if too much condensation builds up, it can cause the wood to rot
away, especially with an outdoor shed.
Also known as the built-up roof (BUR), this type of flat roof features three or
more layers of waterproof material, mixed in an alternating fashion with hot tar
and a layer of smooth stone-like gravel.
To guarantee the material stays secure, most of these materials come as peel-and-stick
systems that are easy to apply.
Also known as EPDM (ethylene propylene diene monomer), this is natural
rubber – the kind you might find on a car tire or an inner tube.
Rubber EPDM membrane other exterior covering).
Insulation (for the warm flat roof only).
You will then add a plywood covering over the joists, what some home
professionals refer to as the “decking.
Again, the width of the decking will depend on a number of factors that
will impact how sturdy the roof is.
Below is an easy-to-follow manual for building flat roofs, including
a guide to flat roof framing and installation with plenty of details
and specifications about the frame.
So every flat roof actually has a gentle rise and fall created by a “frame”
that enables water to run off the roof naturally, and thus avoid any
problems caused by weeds or other plant matter starting to grow on the roof.
You will want to make sure that there is at least a 1/8-inch gap at all the
joints to allow for contraction, expansion and the natural movement of the roof.
You can do this with an IsoBoard, which is a piece of 1/2-inch-thick rigid
foam with a special fiberglass backing.
During the installation, you must ensure that no water is able to pool and collect at
any inside corners of the roof, especially if the roof includes a parapet, which is
a very short wall common around flat roofs.
The goal is to cut a piece that is big enough to cover the roof as well as leave an
additional 9 inches around the entire roof.
Now it’s time to go back over the roof make sure there are no air bubbles.
And, to prevent the vertical sections from peeling off the walls,
you may need to screw on metal brackets known as termination stops.
As a last step of installation, you can nail down a custom lead-coated copper
flashing over the front edges of the roof, then glue down a 12-inch strip of uncured
rubber over the flashing’s top nail edge.
There are a number of pros and cons for any type of flat roof – either warm or
cold – that you may decide to install yourself with the help of a manual.