General information
Ridge caps are hot-dip galvanized metal sheets designed to cover the CGI sheets at the top of the roof. They can have many shapes and sizes. It is recommended to use ridge caps whose wings are 15 cm minimum, in order to ensure a good overlap of the CGI sheets.
Selection:
The thickness and zinc coating of the ridge caps must be identical to that of the CGI sheets.
Quality control, safety and storage: identical to CGI sheets
Basic indications regarding the quantity of ridge caps per roof:
Total quantity of ridge caps to order must include the overlapping of each piece with the next one which is 11-17% of the length to cover:
- Depending on the roof pitch, as indicated in the table below.
Percentage of overlapping if several ridge caps for the entire roof slope:
|
Roof pitch |
Overlap (m) |
Percentage of overlapping |
|
Roof pitch < 15° (26%) |
0.30 m |
17% overlapping |
|
Roof pitch ≥ 15° (26%) |
0.20 m |
11% overlapping |
To have a good approximation of the quantity of CGI sheets needed to cover a gable roof (pitch = 20°, wind speed > 150 km/h), you need to:
- measure the length of the roof (example: length of roof = L = 6.6 m)
- use this formula to determine the number of ridge caps needed to cover the roof slope:
|
Formula to determine the number of ridge caps needed to cover the roof slope |
|
N = L / [length of ridge cap x (1 - % overlapping)] |
|
N = Number of ridge cap |
|
L = length of roof |
|
length of ridge cap = 1.8 m |
|
% overlapping = percentage indicated in table above |
- Example: the percentage of overlapping in our case is 11% as roof pitch is 20°
N = 6.6 / [1.80 x (1 – 0.11)] = 4.12 ridge caps
- round up this value to get the quantity of ridge caps to cover the gable roof (example: 4.12 à 5 ridge caps)
Usage:
Ridge caps are placed last on the roof after the CGI sheets and the fascia caps or hip caps. Ridge caps can be used as hip caps for hipped roofs.
The overlap between the CGI sheets and the ridge cap should be at least 0.15 cm (6 inches).
Assemble the ridge caps on wooden frames with roofing nails (see item EHDWNAILRS01). The quantity of roofing nails depends on the wind speed, location of the shelter and thickness of the laths/battens/purlins used. The values mentioned in the table are approximate. They were calculated for a shelter with a 15-30° gable roof pitch built in a rural area with low vegetation, using a 38mm thick lath/batten/purlin. If the laths are thinner, then you need to multiply the quantity of roofing nails by 2.
|
Wind speed (km/h) |
Number of roofing nails on ridge cap per corrugation (per m of ridge cap) |
|
wind speed < 120 km/h |
roofing nails every other corrugation (3 roofing nails /m) |
|
wind speed < 150 km/h |
roofing nails every other corrugation (4 roofing nails /m) |
|
wind speed < 180 km/h |
roofing nails every other corrugation (5 roofing nails /m) |
|
wind speed < 210 km/h |
roofing nails every corrugation (8 roofing nails /m) |
|
wind speed < 250 km/h |
Use roofing screws with 30mm sealing washer (7 roofing screws /m) |
For a more accurate quantity of fasteners/fixings needed to securely attach the ridge caps to the roof, it is highly recommended to use the Roof Estimate Form (Excel spreadsheet) provided with the CGI sheet roof covering manual (link to be included when known).
Specifications
identical to CGI sheet except the one below:
|
Item |
Required value |
Description / note |
|
Length (imperial system) |
6ft (1.83 m) |
Most common from 6 – 10ft (1.83 – 3.00 m), as per contract. |
|
Length (metric system) |
1.80 m |
Most common from 1.80 – 3.00 m (6 – 10ft), as per contract. |
|
Width |
0.33 m (13 in) |
2 wings of 0.165 m (6.5 in) |