Polycraft 5kg Fibreglass Repair Kit Review: a no-nonsense bundle for serious DIY repairs

I picked up the Polycraft 5kg Fibreglass Repair Kit to sort out two jobs: a leaky GRP shed roof and a crack in an old fibreglass pond. So this isn’t theory – I actually used a decent chunk of the kit over a couple of weekends. I’m not a professional laminator, just a fairly confident DIYer who’s done a few resin jobs before, mostly on cars and a small boat. I wanted something with enough material to do more than a tiny patch, without having to buy resin, mat, catalyst and tools all separately.

First impression: this is a properly sized kit, not a toy starter pack. The 5kg of resin plus the 450gsm chopped strand mat and surface tissue is enough for real repairs – roofs, decks, big panels – not just a tiny ding on a bumper. Everything came in one box: resin tin, MEKP bottle, mat rolls, tissue, roller, brushes, mixing pots, gloves, the lot. It feels like the sort of bundle you’d put together yourself if you knew what to buy.

In use, it’s pretty straightforward, but you do need to know the basics of fibreglass work: surface prep, mix ratios, working time, and safety. The kit does include clear instructions, but they’re more of a reminder than a full course. If you’ve never touched resin before, you’ll want a couple of YouTube videos open while you work. Once I’d planned out my mix amounts and cut all the mat in advance, the actual job went smoothly.

Overall, my first takeaway is this: it’s not fancy, but it’s complete and functional. The resin cures as expected, the mat is good quality, and the extras (roller, pots, brushes) are decent enough that you don’t feel you’ve overpaid for junk. It’s not perfect – I’ll get into the small annoyances – but if you’ve got a mid-to-large fibreglass job to do, this kit gives you plenty to work with.

In terms of value, this kit sits in a sweet spot. For the amount of resin and glass you get – 5kg of Lloyd’s approved resin plus a decent amount of 450gsm mat and tissue – the price is pretty reasonable compared to buying everything separately. If you went to a composites supplier and bought resin, catalyst, mat, tissue, roller, pots and brushes on their own, you’d probably end up similar or slightly higher once you factor in shipping and minimum order quantities.

Where the kit really makes sense is if you have several medium jobs or one larger job: roof sections, boat repairs, a couple of big car panels, or a pond plus some odds and ends. If you only have a tiny repair, this 5kg version is overkill – you’ll be storing half a tin of resin for ages, and polyester doesn’t last forever once opened. In that case, one of the smaller size options they mention in the listing would make more sense. But for what I needed (roof + pond, and still some left over), it felt like good value.

One thing to keep in mind: the tools included are decent but not premium. If you’re going to do a lot of fibreglassing, you might eventually want a better roller or more brushes, but for occasional DIY use, what’s in the box is enough to avoid extra purchases. That’s part of the value: you’re not running back out for a roller or scrambling for mixing pots mid-job.

Overall, I’d rate the value as good, not mind-blowing. You’re paying for convenience and a sensible bundle, not bargain-basement components. If you know you’ll use most of the 5kg and you want a one-shot purchase that covers pretty much everything, it’s money well spent. If you’re ultra-budget and already own tools and pots, you could probably shave a bit off by piecing things together yourself, but you’ll spend more time and effort doing it.

The heart of a kit like this is the resin and the glass, and that’s where I paid the most attention. The polyester resin is Lloyd’s approved, which basically means it’s suitable for marine use. I can’t test the certification obviously, but in practice it behaved like a solid, general-purpose laminating resin. Viscosity is medium: not too runny, not too thick. It wets out the 450gsm mat without fighting you, but you still have a bit of control so it doesn’t just run everywhere, as long as you don’t overload the brush.

The 450gsm chopped strand mat is good. Fibres are consistent, not clumpy, and it cuts cleanly with decent scissors. When you wet it out, it doesn’t fall apart into a mess like some cheap mats I’ve used before. It conforms reasonably well to curves, but if you’re doing tight corners or complex shapes, you’ll still need to cut smaller pieces and layer them. For the roof, which was mostly flat with some slight dips, it was perfect. For the pond, I had to work a bit more in the corners, but nothing out of the ordinary.

The surface tissue is light and easy to handle. I used it as a final layer on the pond repair to reduce the print-through of the heavier mat. Once cured and sanded, the surface was much smoother and easier to prep for finishing. If you don’t care about appearance, you could almost skip the tissue, but it does give a nicer result, especially if you’re going to paint over it or want a neater finish on something visible, like a boat deck or a panel.

Overall, I’d say the materials quality is pretty solid for the price bracket. This isn’t boutique resin or special low-odour stuff – it’s standard polyester with a strong smell and normal styrene content. But it cures hard, bonds properly to prepared GRP, and the mat and tissue don’t feel cheap. For DIY repairs on boats, roofs, car panels, and ponds, it’s exactly what you’d expect from a basic professional-grade kit.

The packaging is basic but practical. The resin comes in a metal can, properly sealed, and the MEKP catalyst is in a small plastic bottle with a child-resistant cap. Both arrived intact, no leaks, no sticky mess in the box. The mat and tissue are rolled and wrapped in plastic. Nothing fancy, but you don’t really need fancy for something that’s going to smell up your workspace anyway.

The cardboard box itself is just a standard shipping box, not a retail display. Inside, things were reasonably organised, though the mat rolls wanted to uncoil as soon as I opened them, so be ready with a bit of space. The tools (roller, brushes, pots, sticks, gloves) were all bagged together. I’d have liked the gloves to be a bit more robust – they’re thin latex, and I tore one putting it on, so have spare gloves of your own if you’re messy like me.

One mild downside: once you open the resin can, there’s no pouring spout or anything. You’re basically tipping it carefully into your mixing pot and hoping you don’t slosh it everywhere. Not a disaster, just slightly awkward, especially with a 5kg tin that’s fairly heavy when full. I ended up decanting a smaller amount into a separate container for easier handling. Also, once you’ve opened everything, storing the mat rolls neatly can be a bit of a pain unless you re-wrap them.

Overall though, the packaging is good enough for what it is. It protects the contents, it’s labelled clearly, and it doesn’t arrive in a chaotic mess. If you’re expecting some kind of polished retail experience, you’re in the wrong category. This feels more like buying from a trade supplier than a lifestyle brand, and I’m fine with that for a fibreglass kit.

I’ve had the repairs in place for a few weeks now, through some fairly typical British weather: rain, cold nights, and a couple of warmer days. So far, no signs of failure. The roof patch hasn’t cracked, lifted or shown any pinholes. Water runs off it fine, and the edge where I feathered it into the existing GRP looks stable. On the pond, the repaired area feels solid under hand pressure, and there’s no flex or creaking when it’s full of water.

Polyester fibreglass isn’t magic, but when done properly it’s pretty tough. The resin in this kit cures hard and bonds well to scuffed and cleaned GRP. I keyed the surfaces with 80-grit, cleaned with acetone, then laid up two to three layers of 450gsm mat depending on the area, followed by tissue where I wanted a smoother surface. That build-up feels substantial. I’d be more cautious using it on parts that flex heavily, like some car bumpers, but for roofs, hulls, ponds, and other fairly rigid structures, it’s fine.

Because it’s Lloyd’s approved resin, in theory it should handle marine environments reasonably well – constant moisture, some temperature changes, etc. I haven’t slapped a boat back into the sea with this kit yet, but I have no reason to think it would behave differently from other marine-grade polyester resins I’ve used. The key factor for durability is still prep and layup, not just the brand name. If you skimp on surface prep or lay the mat badly, no kit will save you.

Long term, I expect the repair to age like any standard GRP: it may yellow a bit if exposed to UV without paint or gelcoat, and it could hairline crack if the substrate moves a lot. But that’s normal. Based on early signs, I’d say durability looks good, provided you use it for the right type of job and don’t rush the basics.

In terms of handling and curing performance, this kit behaves like a standard polyester system – which is exactly what you want if you’re used to this stuff. Pot life and cure time are quite predictable. At around room temperature, I could touch the laminate without leaving fingerprints in roughly an hour, and it was properly hard and sandable after a few hours. I left it overnight before doing any sanding or adding extra layers, just to be safe.

The resin doesn’t kick off super aggressively, so you have a bit of wiggle room, but you still need to be organised. Pre-cutting the mat and tissue before mixing is basically mandatory. If you try to cut while the resin is in the pot, you’ll waste time and end up throwing away half-gelled batches. The included mixing pots are a good size; they let you control how much you’re mixing each time. I appreciated the syringe for dosing the catalyst – it’s much easier than guessing drops or pouring from the bottle, and it helps keep the cure consistent from batch to batch.

One thing to note: like most polyester systems, this stinks. The styrene smell is strong. Outdoors or in a well-ventilated area, it’s tolerable; in a confined space, it’s rough without a proper mask and good airflow. This isn’t a fault of the kit, just the nature of the product, but anyone thinking they can do this in a closed garage without extra ventilation is in for a bad time. Gloves, eye protection and ideally a respirator are not optional in my opinion, even though the kit only throws in basic latex gloves.

From a performance point of view, there were no nasty surprises: no random uncured spots, no weird colour changes, no brittle, chalky finish. The cured laminate is hard but not overly brittle, sands as expected, and takes filler and paint fine once properly keyed. If you follow the instructions and respect the working times, it behaves predictably. For this type of product, that reliability matters more than any fancy marketing claim.

The kit is pretty straightforward: 5kg of polyester resin, a bottle of MEKP catalyst (about 130 ml), a roll of 450gsm chopped strand mat, a roll of surface tissue, a consolidation roller, three brushes, three plastic mixing pots, mixing sticks, a syringe for dosing the catalyst, and a few pairs of latex gloves. No surprises, but also nothing important missing. For someone like me who hates realising mid-job that I forgot to buy brushes, that’s already a plus.

The resin tin and catalyst bottle are labelled clearly, including the basic mix ratio and safety warnings. The mat comes as two separate rolls: one heavier mat for strength and one light tissue for a smoother finish. That’s actually handy – for the roof I used multiple layers of the 450gsm mat, and on the pond repair I finished with the tissue to get a nicer surface before filler and paint. The tools are clearly “kit grade”, not professional, but they’re serviceable. The consolidation roller is metal and does its job of pushing air bubbles out. The mixing pots are just simple plastic tubs, but they’re the right size for manageable batches.

The instructions are a single sheet, printed in a plain way, nothing fancy. They cover: mixing ratio, approximate working times, and a basic step-by-step on wetting out the mat and layering it. If you’ve ever worked with fibreglass before, you won’t learn anything new, but you also won’t be confused. If you’re brand new, it’s enough to avoid big mistakes, as long as you actually read it and don’t freestyle the catalyst amount. I appreciated that they didn’t overcomplicate it with too much theory.

In short, the presentation is functional and honest. It looks like what it is: a trade-style kit put into a consumer-friendly bundle. No glossy branding, no fancy design, but everything you need is there and clearly identified. For this kind of product, I’d rather have that than a pretty box with half the contents missing.

On to the important part: does it actually fix things. I used this kit first on a GRP shed roof that had started to crack and let water in along one edge, and then on a fibreglass pond that had a long hairline crack and a couple of suspicious soft spots. In both cases, the resin cured properly, the bond seems strong, and after a few weeks of rain and temperature swings, nothing has lifted, cracked again or started to weep.

Mixing the resin and catalyst is straightforward. Using the included syringe to measure MEKP by ml into the mixing pot worked well. At around 2% catalyst, with temperatures in the 15–18°C range, I was getting roughly 15–20 minutes of decent working time before the mix started to gel. That’s long enough to wet out a couple of layers on a small area, but you don’t want to mix huge batches. I stuck to 300–400 ml at a time for the roof and less for the pond. The kit gives you enough pots and sticks to do this in stages without too much hassle.

The consolidation roller does its job: it pushes out air bubbles and flattens the mat well. On the roof, where I had long strips of mat, rolling made a visible difference – fewer bubbles and a more uniform laminate. The brushes are basic but fine for stippling resin into the mat. You’re not going to clean and reuse them; you’ll bin them after each session, which is normal for this kind of work. I didn’t have any issues with the resin staying tacky when I kept to the recommended ratio and mixed thoroughly.

End result: both repairs feel solid and watertight. The pond held water for over two weeks with no drop in level beyond normal evaporation, and the roof stopped leaking completely after the first proper rain. I’ll only know about long-term durability after a year or two, but based on how hard the cured resin is and how well it adhered to the prepped surfaces, I’m not worried. For practical repairs, it absolutely gets the job done.