Insulated sandwich roof panels, also called composite roof panels, combine a profiled steel outer sheet, an insulating core and a steel liner in one panel. They go on quickly, but the finished roof is only as weathertight as the installation. This guide covers the key steps from the Joris Ide installation guide, from delivery to the final flashings. You can download the full guide at the bottom of this page. For panel options, U-values and fire ratings, see our insulated roof panels page.
Panel essentials for installers
|
Specification |
Value |
|
Cover width |
1,000 mm |
|
Outer sheet profile |
45/333/1000 trapezoidal |
|
Outer sheet thickness |
0.60 mm (0.50 or 0.75 mm on request) |
|
Liner thickness |
0.40 mm |
|
Minimum roof pitch |
4° after deflection |
|
Watertightness |
Tested to 1200 Pa (standard requirement: 600 Pa) |
PIR gives high thermal performance with a thinner, lighter panel.
Mineral wool is heavier but brings non-combustibility and better acoustic performance.
The core you choose affects lifting and handling, so check panel weights before delivery day.
Before you Start: Delivery & Storage
Space the forks so the overhang is less than 2m at each end.
Use a wide carriage with about 4m between forks.
use an extra-wide carriage with about 6m between forks.
Packages must be lifted with a lifting beam and suction cups or magnetic support on a crane. A vacuum lifter is a fast, safe way to place roof panels. Mineral wool panels are heavier, so each lift can handle a shorter length.
Storing on Site
Store packs on a flat, dry, stable surface, under cover and ventilated, out of sun and rain.
Raise packs off the ground and tilt them lengthways on timber wedges at least 150 mm wide. Aim for a 10% tilt and never less than 5%, so water drains away.
Remove the protective film within one month of delivery, or straight away if the panels are in direct sunlight.
Carry panels on their edge, with the interlocking (male) side facing down.
Check the roof structure
Panels can be fixed to steel, timber, or concrete with metal inserts. The top of every support must sit parallel to the roof plane. The minimum pitch is 4°, and below that no penetrations such as rooflights or flues are allowed. Joris Ide recommends a layout study for each project, submitted to them for checking.
Minimum Support Widths
|
Support |
Steel (min 1.5 mm thick) |
Timber (min 80 mm high) |
Concrete with metal insert (min 2.5 mm) |
|
End support |
50 mm |
50 mm |
50 mm |
|
Intermediate support |
50 mm |
50 mm |
50 mm |
|
At an end lap |
65 mm |
90 mm |
65 mm |
Fixings must be at least 15 mm from the edge of the support and 20 mm from the end of the panel.
Step-by-step Installation
Run a string line along the roof edge before laying the first panel. Every panel follows the first one, so getting it straight keeps the whole roof aligned.
Peel the foil off each panel before fixing. Foil left on traps moisture and stops sealants bonding.
Start at the end of the roof opposite the prevailing wind and rain. Each panel should overlap the previous one so wind-driven rain is pushed over the joints, not under them.
Press each new panel firmly into the previous one so the undersides line up before you fix it. Fix through to the structure in every valley, or every second valley at intermediate supports. Stitch the side laps together with stitching screws every 300 mm, with no more than 500 mm between them.
Use a drill with a depth stop or torque limiter, and check its setting during the job.
- Too loose: the washer doesn't seal, so water gets in and the panel can move.
- Correct: the washer is slightly compressed and the panel is not dented.
- Too tight: the panel deforms, the washer is damaged and corrosion can follow.
Where two panels meet along the slope, the upper panel must overlap the lower one by at least 30 mm on the support, sealed with butyl. Check the overlap needed for your roof pitch against Building Regulations.
Keep cutting on site to a minimum. Use a jigsaw for panels and a nibbler for flashings, and avoid any tool that throws hot sparks onto the coating. Never use a chainsaw. Sweep up all straight away, because left behind it rusts and stains the panels.
Which sealant goes where
Between panels and the supports. It levels out small height differences, keeps joints airtight and stops steel touching steel.
Compresses to seal gaps under the profile and around flashings against water, dust and dirt.
A fully watertight adhesive sealant for panel laps and joints. It flexes as the steel expands and contracts.
For irregular or stepped joints where butyl or tape can't follow the shape.
Ridges, Gutters & Flashings
- External ridge cap where two slopes meet
- Ridge course where the roof meets the wall cladding at the same height
- Toothed pent ridge where a mono-pitch roof runs up to an existing wall
At low pitches (around 4°), use a raised edge detail under notched ridge sheets.
- Eaves gutter flashing for mono-pitch roofs
- Valley gutter where two slopes drain inwards
- Parapet gutter where an eaves gutter isn't possible
Fit insulation and closures at every junction to limit thermal bridging, especially over heated or air-conditioned spaces. Flashings can be made in the same colour and coating as your panels.
We make flashings in-house to any measurements, in the same colour and coating as your panels.
Trapezoidal roof panels can also be used as wall cladding:
- Lay panels from the bottom up, working left to right.
- Vertical end laps should be 100 mm, fixed in every valley and sealed with butyl.
- Side laps should be stitched in the crown at no more than 450 mm centres.
- External flashings should be fixed with stitching screws every 500 mm.
The building owner should have the roof inspected at least once a year:
- Clear leaves, moss and debris.
- Keep gutters and outlets flowing.
- Touch up any damage to the coating, and watch for early corrosion at gutter edges and end laps.
- Check that flashings and seals are intact.
Download the full installation guide
The full guide includes detailed drawings for every junction, plus span tables and parapet limits.
Frequently Asked Questions
4° after deflection. Below this, no penetrations such as rooflights are allowed.
Start at the end opposite the prevailing wind and rain, so each panel overlaps the previous one away from the weather.
Yes, with a jigsaw, keeping cuts to a minimum. Avoid tools that throw sparks, and clear all swarf straight away.
Every 300 mm along the side laps is recommended, with no more than 500 mm between screws.
Yes. Lay them bottom to top with 100 mm vertical laps, stitched at no more than 450 mm centres.
Need panels, flashings or advice?
Tinman Steels has been supplying steel roofing from Tamworth since 1987. We supply insulated roof panels alongside the flashings, closures and sealants to finish the job, with flashings made to match your panel colour.