How to install a low pitch roof

Written by henri bauholz
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Rolled roofing can usually be installed on a roof with a low pitch, but not on a flat roof. In other words the roof must have a slight pitch, in order to install rolled roofing. Also the roof needs a solid wood deck underneath, so that it will take the nails. Planking with spaces between each board is unacceptable.

Skill level:

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Things you need

  • Rolled roofing
  • Tar paper
  • Ladder
  • Utility knife
  • Roofing blades
  • Roofing tar
  • Trowel
  • Galvanized roofing nails
  • Roofing nails with washers (for the tar paper)

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  1. 1

    The first thing to do when installing a roof of any type is to calculate the size of the area of the roof. To do this, simply climb onto the roof and measure to the nearest foot, the width and length of the surface area. Multiply the two numbers together and now you have the area of the roof. Next multiply the total by 20% and add these two numbers together. That is how much rolled roofing you have to buy to cover the area of the roof.

  2. 2

    Proceed to your local building supply company and pick out a colour of rolled roofing for your roof. You will also need a comparable amount of black tar paper (also called building paper or felt paper), some plastic roof tar and galvanised roofing nails. You will need 2.27 Kilogram of nails for approximately every 200 square feet. For a new roof you can use 1 ¼” nails and 1 ¾’ nails will work if you are laying the rolled roofing over top of an old roof. If there is more than one layer of old roofing on the structure, then you will need to remove all old layers of roofing first.

  3. 3

    Once you are back at the site, you will have to remove all debris before you start laying down the black felt paper. Heavy weight building paper is always recommended. Galvanised strips of metal flashing should cover all the roof’s edges before you begin.

  4. 4

    Begin this roofing project by laying down a strip of felt paper that goes from one end of the bottom of the roof to the other end. Let the paper hang over the side edges for a little ways, but make sure the bottom of the tar paper is just back a short ways (one inch or less should do) from the bottom edge of the roof. Secure the tar paper with a few nails or you can use one of those mechanical tacking hammers, to save time. Now cut the two sides, so they also sit back a small distance from the edge and nail the sides. Go ahead and nail the entire piece of felt paper. Instead of roofing nails you can use special nails (Instead of an extra-large head, they have big round washers attached at the head to hold down the felt) Please note that a retractable utility knife with hooked blades (also called roofing blades) is the ideal tool for cutting both the tar paper and the rolled roofing. The second strip goes down just like the first, except you will be overlapping the first piece of felt paper by half (18” for a 36” wide roll). This is called half-lapping and you continue this right up to the peak of the roof. At the peak just carry the last strip of tar paper right on over to the other side and secure it tightly. If you come to a chimney, you will have to notch the paper to fit around the brick structure, but with a vent you can cut a hole for the vent and keep going. Note that the hole will be slightly elongated.

  5. 5

    Next comes the final layer of rolled rolling which is applied in much the same manner, except is always held down with galvanised roofing nails and sealed with roof tar. The roof tar is a petroleum-based substance that comes in a five-gallon container. It is applied with a trowel.

  6. 6

    Go ahead and unroll your first roll of rolled roofing. If the roll has two different surfaces, the asphalt surface will go towards the bottom and it will be exposed, when the roof is done. The rolled roofing should overhang all the roof edges by about a half an inch. Set this piece of rolled roofing in place and make a vertical cut in the proper place, if the roll of roofing is longer than the section of roof. Place a few nails along the top edge to hold the piece of asphalt in place and then carefully apply a strip of tar around the bottom and both sides. The layer of tar should be covered by the top layer of rolled roofing, but the heads of the nails will be exposed, so be neat with the nailing pattern. Now nail the whole piece down tight placing nails about every six inches along the bottom and sides.

  7. 7

    If your roll stops in the middle of the roof, then you need to make a vertical joint. Just overlap the next piece of rolled roofing by about one foot and that will be your joint. Just remember to apply roof cement between the two layers of roof and as always nail tightly.

Tips and warnings

  • Wear tennis shoes so you do not mark off the roof.
  • Do not apply rolled roofing during the middle of a hot summer day. If the day time temperatures are excessive, then do the work in the early morning or late evening.
  • Lighter coloured roofs are harder to keep looking clean.
  • Don't fall off the roof.
  • Make sure all vents and chimneys are sealed correctly.

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