Topped With Green
Green roof gardening is a fairly new concept in South Africa but planting on roofs for aesthetic and cooling purposes is not as difficult as it seems. We tackled a small area from scratch to show you how easy it is – before you dash off to your Hardware Store to stock up and design your own ‘green’ roof.
What You Need
4 x truss hangers (90 x 38 mm)
8 x rawl bolts (10 mm)
4 x CCA-treated pine rafters
(1460 x 114 x 38 mm)
3 x CCA-treated pine purlins
(2135 x 76 x 50 mm)
1 x CCA-treated cross-beam support
(2130 x 114 x 38 mm)
2 x CCA-treated poles
(75-100 mm, 2100 mm long)
2 x CCA-treated roofing timber
(152 x 38 x 1605 mm)
1 x CCA-treated roofing timber
(114 x 38 x 2135 mm)
3 x IBR Roof sheets (900 x 1570 mm)
20 x nails (100 mm)
32 x screws (4 x 30 mm)
33 x roof screws (6 x 90 mm)
8 x coach screws (10 x 100 mm)
2 x post base plates
4 x D-shaped gutter brackets
1 x D-shaped gutter (2130 mm)
2 x gutter stop-ends
1 x gutter outlet
1 x gutter shoe
2 x gutter bends (75 mm)
1 x gutter downpipe (1590 mm)
1 x piece gutter downpipe (75 x 150mm)
1 x piece gutter downpipe (74 x 100 mm)
1 x tube PVC Weld
1 x bag small gravel for drainage
5 x bags potting soil
5 litres ABE Super Laycryl & Membrane
1 large block palm peat
Selection of sedum, green grasses and succulents
Tape measure, hammer drill with 10 mm drill bit, electric drill, saw, bevel square, pencil, combination spanner, carpenter’s hammer and cordless drill with 6 mm drill bit.
Step 1 Measure up the wall for the truss hangers – 2500 mm from the ground and 700 mm apart. Mark and drill holes into the wall using the 10 mm drill bit. Secure the truss hangers with rawl bolts.
Step 2 Cut the four rafter timbers at each end at 75°. Place the timbers into the truss hangers and secure using six screws for each rafter.
Step 3 Position the support poles on the inside of the two outer rafters. Use the base plates to secure into the flooring. Mark the position of the base plates and drill holes into the floor for the rawl bolts. Secure the base plates to the floor and insert the support poles. Secure the poles to the base plates with screws.
Step 4 Secure the rafter timber to the outside of a support pole using a coach screw with a pre-drilled hole. Secure the other side in the same way.
Step 5 Take the supporting cross-beam, line it up underneath the rafters and secure it to the support poles using the coach screws. To secure the intermediate rafters to the support beam use 100 mm nails.
Step 6 Position the purlins – one at the top against the wall, one at the bottom and the other in the centre. Nail onto the rafters using 100 mm nails.
Step 7 Fit the gutter brackets on the front of the structure spaced evenly and lining up with the rafter timbers. Glue the two stop-ends onto the gutter and clip the system into the brackets.
Step 8 Place the roof sheets into position. Drill 6 mm holes through the sheeting into the purlins and secure with roofing screws. Drill small holes in the end of the roof sheeting to allow water to drain into the gutter.
Step 9 Cut the two roofing timbers at a 75° angle on the one side. Place the angled piece against the wall with the roofing timber set at 50 mm from the top of the rafter down and along the length. Secure with nails. Complete both sides before adding the 2135 mm panel on the front to make it flush with the top of the side timbers and secure with nails.
Step 10 For the down pipe system, place the outlet on the gutter and mark a circle on the gutter from the inside of the outlet. Drill the gutter with circles of holes to prevent leaves and debris from collecting, or you can cut out the entire circle.
Put PVC Weld onto the outlet connection and click onto the gutter. Use the 150 mm length gutter down pipe to fit into the outlet connection using PVC Weld to secure it onto a bend. Use the 100 mm length of gutter down pipe to fit onto the other side of the bend and then onto the 1590 mm length. of down pipe. Attach the shoe to the end of the down pipe. Secure all connections with PVC Weld.
Step 11 All four sides, on the inside of the roof at the top where the plants will be planted, need to be sealed and waterproofed using Super Laycryl painted on membrane as per the manufacturers’ instructions. You can even go over that with some green paint!
Step 12 Place a layer of gravel on the gutter-side for drainage. Mix together palm peat and potting soil and use this as a planting medium for the plants. Make sure the medium is damp when you are planting. Choose a variety of hardy plants like sedums, other succulents and grasses that have a shallow root system and group colours and textures together to form a pleasing pattern. Water the “green roof” garden well when completed and thereafter water it once a week.