Getting your roof edges right is probably the most important bit of any fibreglass roofing job. You can lay a perfect GRP surface but if water finds its way in through trims or flashings that weren't fitted properly you'll have to start all over from scratch. We will help you in choosing the correct trim to your project, where to install it, and how to install it. This guide breaks down everything from simple drip edges to those tricky corner joints and wall penetrations. No matter if you're dealing with a simple flat roof or one that's a bit more complicated with multiple levels and those awkward angles - we've got you covered. Getting to the Bottom of Your Trim Options When you're shopping for fibreglass roofing supplies you'll notice there's a whole range of trims to choose from. Each one has its own job to do, and getting the right one is going to make all the difference for the looks and the waterproofing. The A200 Drip Trim This is your go-to for the lowest edge of the roof where water flows into the gutter. The A200 measures 3 metres long with a 90mm drop and works perfectly for most standard applications. It creates that essential drip edge that stops water from running back underneath your roof deck. Click here to see more information about The A200 Drip Trim. The B260 Raised Edge Trim Think of the B260 as the bigger brother to the A200 - it's got a 90mm faceplate for when you need a bit of extra height to stop water running off in the wrong direction. It's just as happy to work with its A200 cousin, so you can chuck them both on the same roof. Click here to see more information about The B260 Raised Edge Trim. The D260 Wall Fillet This trim is what you need where your roof butts up against a wall. It creates a 45-degree angle that deflects water away from the vertical surface, stopping moisture from creeping up the brickwork. The D260 wall flashing trim comes with a 140mm upstand and is 3 meters long. The D260 works with corner trims (C3 internal and external) for neat finishes at wall junctions. Make sure you leave that recommended 25mm expansion gap between your roof deck and any brickwork before fitting. Click here to see more information about The D260 wall flashing trim Planning Your Trim Layout Before you start cutting and fixing anything, spend time planning where each trim goes. When tackling a roof try taking a good long walk around the entire thing and take a close look at all the edges, corners and wall junctions while you’re at it - don't just stop at the roof itself. Do that and you'll be less likely to reach the middle of the job and suddenly realise you’ve forgotten a critical bit. Every section should direct moisture towards the gutter without creating any pools or backflow. Mark out where your drip edges need to sit and where you'll need raised trims to cope with different levels. Tackling Corner Joints Corners are where most DIYers get nervous, but pre-formed corners have made this job so much easier. You don't need to mess about with on-site mitre cutting anymore - just grab the right corner piece and you're sorted. For a visual guide on how to handle corners properly, watch Part 2: Fibreglass Roof Trims External Corners The C1 external drip corner works with both A200 and B260 trims. These pre-formed pieces ensure you get a neat, watertight finish at any change in direction. When you're fitting them, nail the corner to the deck at each end and in the middle. Then seal the joins between the trim and corner with a thin line of polyurethane adhesive. Click here to see more information about The C1 external drip. Internal Corners The C4 universal internal corner handles inside angles where two sections of raised trim meet. Application is pretty much identical to external corners - fix it securely, then seal all the joints properly. Click here to see more information about The C4 universal internal corner. Wall Junction Corners For where a flat roof meets an abutting wall, you'll want the C2 fillet to trim corner. This clever upstand works with the A200, B260 and D260 profiles, comes in left and right handed and has a height of 120-140mm depending on what you need it for. Click here to see more information about The C2 fillet to trim corner. Handling Roof Penetrations Pipes, vents and other bits that stick out of your roof - let's face it, they can be a real nuisance. Add extra layers of protection around each one to keep water out. Cut the fibreglass matting to fit tightly around the opening. Then, cover it well with resin, making sure to reach the edges. You might need to add extra layers of mat in these areas for reinforcement. For anything that moves or expands (like certain pipe types), you'll want to build in a bit of flexibility. Use a flexible sealant like Ultra-Flex GRP around these areas instead of standard rigid resin. This creates an elastomeric seal that can flex with movement without cracking. Installation Steps That Actually Work New to fibreglass roofing? Our complete video tutorial series walks you through every step from deck prep to final topcoat. Preparing Your Deck Your roof deck needs to be spot-on before any trims go down. Check that fascia boards sit flush with the top edge of your roof boards. Any wonky bits now will show up later as gaps where water can get in. Fixing Methods Most trims are attached directly to the roof deck using nails or staples. Use 13mm galvanized clout nails, or use a gas nailer to make it faster. Begin at one end and place a nail every 20cm along the trim length. This holds it firmly against the board without any bending. Some trims, such as flat flashings and angle fillets, need polyurethane (PU) adhesive rather than just nails. Put a line of PU glue on the back of the trim, roughly every 20-30 cm. Press it down firmly to spread the glue. Then, add a nail at each end and one in the middle to hold it in place while the glue dries. Do you want to see it working? Watch our easy video guides, one step at a time: Part 2: Fibreglass Roof Trims - Cut and Fit GRP Edges Part 3: Fibreglass Roof Bandages - Laminate Trims & Joins. Applying the Laminate After you secure all your trims, you can begin laying the fibreglass matting. The mat should cover the trims completely, so ensure it's tightly fitted into all the curves and angles. See exactly how it's done in Part 4: Fibreglass Roof Laminate. Topcoating Your Trims Getting a smooth, professional finish on your trims takes a bit of practice. Rather than trying to explain every detail, we've put together a complete visual guide that shows you exactly how it's done. Watch our video tutorial: Part 5: Fibreglass Roofing Topcoat - GRP Flat Roof Colour This video walks you through the proper roller technique, shows you how to protect your fascia boards, and demonstrates the best way to get that clean finish on all your trim faces. Common Mistakes to Avoid Don't skip the expansion gap between your roof deck and walls - that 25mm space matters. If you don't have it, your roof won't adjust to temperature changes, and you'll get cracks. Never use silicone sealant or general-purpose mastic to fix trims. These products don't bond properly to GRP and will fail over time. Stick with proper polyurethane adhesive designed for fibreglass roofing. Pay attention to how you overlap your materials. Water should always flow down and out. If you're not sure about a junction, think about where the water will go when it rains a lot. Choosing Quality Materials The trims and flashings you pick will sit on your roof for decades, so don't cut corners on quality. Look for GRP trims with a high-adhesion finish that bonds properly to liquid-applied systems. At Apex Fibreglass Roofing Supplies, our trim products are made to fit together perfectly. If you need a full roofing kit or just some trim pieces for a repair, you can count on materials that professionals rely on. When to Ask for Help Complex roofs with lots of awkward angles aren't always straightforward DIY territory. If your walls are different heights, have unusual openings, or your roof shape is not standard, just ask for help. We're here to help you get what you need. A quick phone call to our team can save you from ordering the wrong parts or running into problems halfway through your job. Give us a ring on 0800 612 7903 (UK) and we'll talk you through exactly what you need. Our fibreglass products come with free expert advice to make sure your project goes smoothly. Checking Your Work Once everything's installed and cured, do a thorough inspection before you call it done. Look at every corner joint and wall junction up close. Check that all your flashings sit properly in their chases and that you haven't missed any spots with the topcoat. Run a hose over different sections of the roof to see how water flows. It should all move smoothly towards the gutters without pooling anywhere. Pay special attention to areas around penetrations and where different roof levels meet. Conclusion When trims and flashings are done properly, a roof will last and no one will have to repair it all the time. Apply good fixing techniques and ensure that the sealing task is done. Ready-made corners come in handy when an individual has an intricate roof design. High-quality materials supplied by Apex Fibreglass Roofing Supplies will help you in your work and allow doing it properly. It does not matter whether it is a simple extension or a complicated roof, the main point is to ensure that water moves correctly and close all openings. Your fiberglass roof will save you in the weather as long as you install your trims and flashings in place.
