7. Laying the main laminate
The order of laminating work on the roof is as follows
- Mask off areas to protect against resin spray from rollers
- Laminate small details – around pipes, into down pipes, through apertures, snow boxes, trim overlaps, trim-to-corner joins and in-situ fabricated corners
- Bandage trim to deck joint with 450g x 75mm CSM bandage (tape). The bandage should be applied so it lands equally on the trim and the deck along the length of the trim.
- Laminate all board-to-board joints on square edge/gapped applications. Remember masking tape must be applied to prevent the ingress of resin between boards. (There is no need to tape or bandage T&G boards)
- Apply the main laminate to the deck.
Applying The Main Laminate
(See ‘How To Laminate’)
- Is this your first attempt at laminating? Have you made a test piece?
- Do you want to begin in the shade or in the sunshine? Where will you position your ladder?
- Option 1. All board-to-board and trim to deck bandaging can be completed before beginning the main laminate and may (or may not) reach an initial cure stage before the main laminate is applied.
- Option 2. Alternatively the bandaging can be carried out locally just before the main laminate is laid allowing better consolidation between the bandage and the laminate (applied ‘wet-on-wet’ ).
- There is no requirement to overlap the glass layers in the direction of the fall.
- There is no preferred starting point. However we suggest a shorter run perhaps starting at the drip edge (typically the front 3m edge of a 6m x3m garage roof).
- The 3m2 of 600g CSM will require approx 5.4kg – just over 5L/5kg
- 5kg laminates approx 2.7m2 of 600g CSM
- Continue laminating using your pre-cut rolls. Check your work and quantities used as you go. Remember to overlap 50mm – feather edge over cut edge.
- Keep the main laminate on the deck. Other than corners and possibly trim joints the laminate should not be visible from ground level.
- If you want to take a break finish the resin mix you are using. Remove the soft roller head from the handle. Discard the head and clean the handle in acetone. Clean the paddle roller in acetone. Fit a new roller head when you re-start.
- Acetone is extremely flammable. Keep acetone in a sealed metal container available from your distributor. Do not use acetone as a hand cleaner.
- Within 24hrs laminates can be bonded to laminates even if they have reached first-stage cure. After 24hrs sand a 50mm margin for the overlap.
- Allow the laminate to reach a first stage cure before applying the topcoat (as soon as you can walk on the laminate without disturbing thefibres)
Getting a smoother finish
- A GRP roof will never look like a moulded GRP object such as a boat which is produced in a shiny mould. Roofing GRP is a surface application and the texture of the mat should be just visible through the topcoat (it is important to avoid thick topcoat applications which may crack and craze).
- The laminate surface can be made smoother by the addition of glass tissue – a thin glass veil applied from the roll to a wet laminate and wet-out in situ with a soft roller and more resin if required
- An improved finish can be achieved by sanding the laminate before applying the topcoat. Use 40-60 grit aluminium oxide paper. The laminate must be cured sufficiently to allow sanding without clogging.