1 Fix the wall plate
The roof is supported by two main beams of 100 x 50mm (4 x 2in) timber, which can run the length of the carport. One beam is used as a wall plate and is fixed to the house wall with masonry bolts while the other is screwed to support posts erected at the outer edge.
2 Position the posts
You can excavate holes and then bed the posts in concrete, but by far the simplest method - especially if there is an existing concrete base - is to use bolt-down fence support sockets fixed into place with small masonry bolts set into holes drilled into the existing concrete.
3 Fit the main bearer and joists
With the supporting posts securely in their sockets and truly vertical, drill clearance holes for the screws in the face of the outer edge beam. Hold the beam in position and clamp it to the outer faces of the posts, then slot a joist into the notches cut into the beams across the higher end of the roof and use a spirit level to check it is horizontal. When the joist is level, tighten the clamps, and screw the end of the beam to the first post. Repeat the process at the lower end of the roof and then fit the joists. It's worth taking extra time at these first 3 stages to make sure all your posts and beams are striaght and true and that the posts are completely vertical. Making sure of all your work at this stage will make the rest of the job easy.
4 Add the roofing sheets
Lay the first roofing sheet at the down-hill end of the roof with one long edge butted against the house wall and the other overhanging the fascia board at the lower end by about 50mm (2in). Drill 3mm (1/8in) clearance holes in the first ridge above the wall plate and in every fourth ridge above each of the joists. Slip a sealing ring over each screw, insert into the hole and drive into the wood below. Snap on a plastic cover to conceal the screw head. Lay subsequent sheets against the house wall so that the lower end overlaps the sheet you have just fixed by 300mm (12in), and repeat.
5 Sealing the junction between wall and roof
Once the first row of roof sheets has been installed, seal the junction between it and the house wall with self-adhesive flashing tape. First, apply flashing primer to the wall and allow it to become tacky, then peel back the paper backing from the tape and bed one edge against the house wall and let the rest lap onto the roof surface. Work your way along the roof, peeling back the backing on the tape as you go. Cut the tape to length at the end, then go back and press the tape firmly into the roof surface.
6 Check the levels
Throughout the construction process, it is vital that the supporting posts remain truly vertical. Each time you descend from your ladder, check them with a spirit level and make the necessary adjustments. To complete the carport, you could fit gutter brackets and a length of 100mm (4in) wide guttering to the fascia board at the downhill end of the roof; attach a downpipe to the gutter outlet and run it to a nearby gully.
Safety Tips
- Make sure any power tools are plugged into an RCD adaptor or RCD socket outlet.
- Set up stepladders and other access equipment on level ground and take care not to over-reach when working at heights.
