Flat Roof Installation Instructions

A flat roof can serve as a balcony or terraced area.

Unlike a standard pitched roof, constructing a flat roof is relatively easy, and can be carried out by someone who is experienced in DIY. Flat roofs have a number of advantages over typical pitched roofs: they are more cost-effective, and allow full use of the space created - unlike pitched roofs, which may result in rooms with sloping walls. They are low maintenance, and can double as a balcony area.

Things You'll Need

• Underlay felt
• Nails
• Hammer
• Tape measure
• Stanley knife
• Felt adhesive
• Top sheet
• Brush
• Heavy duty gloves
• Cutting board

Instructions

1. Remove all existing debris from the underlying area; you may need to replace areas that have become damaged over time.

2. Starting at the lowest edge of the roof (if it slopes), lay the underlay felt onto the decking by nailing it in place at 6 inch centers. You will need to measure and trim to fit the roof, cutting the felt with the Stanley knife. Overlap each layer of felt slightly with the next roll, so that rainwater will not run into any cracks between the felt.

3. Lay a second layer of underlay felt, this time securing it to the first layer using adhesive. The joins of this layer must not be in the same place as the layer beneath. The adhesive should be applied in accordance with the manufacturer's instructions. Overlap each layer of felt by 2 inches over the strip laid before.

4. Overhang a strip of Top Sheet to the edge of your flat roof - securing it by nails - so that it hangs down to within an inch of the gutter. This will allow rainwater to run off the roof without permeating any of the layers and causing damp-related problems such as rot or mold.

5. Lay the top sheet of felt using adhesive, as you did with the second layer. Again, overlap each strip by a couple of inches.

6. Brush away any grit or debris from your new roof.

Tips & Warnings

• Do not lay a flat roof in wet or cold conditions.

• Unroll the felt at least half an hour before you use it, to ensure it contracts or expands to its final shape.

• Cut felt on a cutting board, never straight on top of the roof.

References

• DIY Data: Three layer Felt Roofing using cold applied adhesive