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Master the Art of GRP Trim Installation

Discover the essential steps for a seamless GRP trim fitting experience, ensuring durability and precision for your roofing projects.

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Step-by-Step GRP Trim Fitting Guide

1

Prepare Your Workspace

2

Measure and Cut Trims

3

Secure and Finish

Common Questions About GRP Trims

Discover the answers to your most pressing questions about GRP trim installation and maintenance, ensuring your roofing project is a success.

How to Fit GRP Trims

How fitting fibreglass trims is an important step in completing a fibreglass roofing installation. The trims help to provide a finished look to the roof, and can also help to prevent leaks by covering any gaps or seams. Installing fibreglass trims involves cutting the trims to size, and then gluing them into place using a suitable adhesive. It is important to take care when fitting the trims, as any gaps or misalignments can allow water to penetrate the roof, causing leaks. It is also important to make sure that the adhesive used is suitable for use with fibreglass, and that it is applied in a consistent and even manner to ensure a strong and secure bond.

Polyurethane Adhesive (PU)

PU adhesive is applied with a skeleton gun to the batten around the perimeter of the roof. A 30mm bead at 300mm centres is sufficient to hold the trims in place. The trims should be ‘rubbed’ into place to ensure good bonding. Joining Trims Trims are either nailed to the decking boards using a 13mm galvanised clout nail or stapled in place with a gas-powered or compressed air stapler. Hold the trim in place ensuring the face is vertical. Drive fixings in at each end, then the middle and then at 200mm centres thereafter.

A170/A200/A250- Drip Trim
The A-type trim is a drip trim, fitted to the lowest edge of the roof usually where the rainwater flows into the gutter. Two support battens should be fixed to the perimeter of the roof to provide space for the gutter to fit behind the trim, with the outer batten attached 10mm lower than the inner batten to allow the trim to sit flush with the roof. Apply PU adhesive to the batten in 30mm beads at 300mm centres, rub the trim into place and nail to the decking. Do not nail through the front of the trim. If the pitch of the roof is only minimal, rainwater is likely to hold behind the trim. A planning machine can be used to take 2mm off the deck to allow the trim to lay flush with the board.
TRIM DETAILS: A170: This is designed for applications where it is not possible to use the larger A200. A200: This is the standard size drip trim.
A250: This drip trim is ideally suited for use on warm roofs
B230/B260/B300- Raised Edge Trim
A single batten is a fixed level with the top edge of the deck. Apply 30mm beads of PU adhesive to the batten every 300mm, rub the trim into place and nail through the top of the trim into the decking. Do not nail through the front of the trim. If a ladder is likely to be leant against a B type trim for regular access to the roof, the trim will need to be reinforced to avoid deformation. The trim can either be doubled up by slotting a section of extra trim within the section where the ladder will be used or it can be reinforced with an extra layer of GRP laminate and then tissue to maintain a smooth finish. Alternately, a wooden batten can be shaped and fitted into the ridge of the trim to ensure that it remains rigid.
TRIM DETAILS: B230: The smallest size of raised edge trim fitted to the edges of the roof to contain and direct the flow of water.
B260: The standard size raised edge trim. B300: Larger raised edge trim for use on warm roofs.
C100/- Simulated Lead Flashing

The C trim is usually fitted into a bed joint of the brickwork or a 35/50mm (depending on the trim type) deep chase cut out with an angle grinder fitted with a mortar chase disc. Apply polyurethane adhesive to the back of the C trim every 300mm. Fit the trim into the slot and press firmly back to the wall to overlap the D trim. Apply a clear silicone sealant along the length of the trim into the slot to seal the trim in. A smooth finish can be obtained by wiping the sealant with a moistened finger. TRIM DETAILS: C100: Standard simulated lead flashing with 100mm vertical face and 35mm wall penetration. Do not topcoat.

D260/D300- Fillet Trim

The D trim is a fillet trim for use against abutting walls. It will also provide expansion and perimeter ventilation and is compatible with C2 and C3 universal corners. Place the D trim against the vertical face and push down diagonally into the corner until the trim fits snugly. Where the D trim needs to be joined it should be bonded with a strip polyurethane adhesive and bandaged together.

TRIM DETAILS: D260: Angle fillet trim with 135 and 70mm flanges. D300: Angle fillet trim with 175mm and 70mm flanges.

F300/600/900- Flat Sheeting

The F trim is a flat flashing, mainly used at the intersection of a pitched roof and flat roof often found on dormers. The F trim should not be laminated over completely as it will crack. It is nailed or stapled to the deck and bent up the roof slope. In this situation, the F trim also acts as an expansion facility and must only be fixed to the deck along the bottom edge. There are many other applications for F trim including vertical details where laminating would be time-consuming, under the feet of air conditioning units to enable re-roofing without disconnecting and use on some parapet wall details etc. The trim should be nailed to the deck around its edges and bandaged over any joins or nail penetrations. Any unlaminated trim can be top-coated with the rest of the roof. TRIM DETAILS: F300/600/900: Flat sheeting supplied in 300, 600 and 900mm widths in 20M rolls.

E280- Expansion Joint E280
is used both to create expansion joints on large roofs (over 50m2 ) and create rolls on any ridge details. It is compatible with C5 closures. An adequate gap in the deck should be cut if necessary, the trim should then be nailed to each end of the decking at 300mm centres. The join over the nails should then be bandaged and the laminate can be applied over the trim. To bond these trims together, or to cap with C5 closures, apply a thin strip of PU adhesive to the inside edge of the overlapping trim and rub into place.
TRIM DETAILS: G180: Flush installation expansion joint and gutter. E280: Expansion joint and ridge roll for pitched roofs.
A195 Internal and External
The AT195 Internal and External trim is used wherever the laminate needs to cover an area which continues perpendicular to another laminated surface. The AT195 Ext is supplied with a high-adhesion finish on its outer fascia and should be used for capping applications. The AT195 Int trim is supplied with a high adhesion finish on its outer fascia and should be used for internal corners. The trim should be nailed at both edges if possible. Always bandage over the join between where the nails penetrate the trim and the decking before applying the laminate. These trims are supplied in 3-metre lengths as standard.
TRIM DETAILS: AT195 Ext: External angle trim. AT195 Int: Internal angle trim.

CRS TOP TIPS Fitting GRP Drip Trims like this prevents standing water.

CRS TOP TIPS Fixing Points for GRP Trims

Watch Our GRP Trim Installation Video

Follow along with our detailed video demonstration to see each step of the GRP trim fitting process in action, ensuring a professional finish every time.

Common Questions About Fitting GRP Trims

Explore answers to the most frequently asked questions about installing GRP trims to ensure a seamless roofing experience.

What tools are needed to fit GRP trims?

To fit GRP trims, you’ll need a fine saw for cutting, a hammer for securing clout nails, and a measuring tape for accuracy. Additionally, a sealant gun is useful for applying adhesive.

How do I ensure a watertight seal with GRP trims?
Ensure a watertight seal by applying a generous layer of GRP adhesive along the edges and pressing the trims firmly into place, ensuring no gaps are left.
Can GRP trims be painted?

Yes, GRP trims can be painted. Use a high-quality exterior paint such as Topcoat suitable for GRP materials to ensure durability and a professional finish.

How do I cut GRP trims to size?

Use a fine-toothed saw to cut GRP trims to your desired length or tin snips, a grinder can be dusty. Measure twice to ensure accuracy and smooth any rough edges with sandpaper.

Are GRP trims suitable for all weather conditions?
GRP trims are designed to withstand various weather conditions, including heavy rain and UV exposure, making them ideal for outdoor use.
How long does it take for GRP adhesive to cure?
GRP adhesive typically cures within 24 hours, but it’s recommended to allow 48 hours for full strength, especially in cooler temperatures.

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