Guttering for a Polycarbonate Roof: What You Need and How to Choose
Fitting an EZ Glaze or polycarbonate roof to a carport, lean-to, veranda or patio canopy is a satisfying job — but there's one part people often leave until last and then get wrong: the guttering. Get it right and rainwater is whisked cleanly away from the structure and your home. Get it wrong and you'll have water spilling over the edge in every downpour, soaking the frame and pooling at the base. This guide explains exactly what guttering a polycarbonate roof needs and how to choose the right type.
Does EZ Glaze come with its own guttering?
No — and that's not an oversight. EZ Glaze (like all polycarbonate roofing systems) is designed so the sheets simply overhang the lower edge by 50–150mm and let the rainwater run off. The guttering is a separate item you choose to suit your roof, which is good news: it means you can pick exactly the right size and style rather than being stuck with a one-size-fits-all part. The sheets do the roofing; standard rainwater goods do the draining.
Self-support or fascia-mounted? Start here
The first decision is how the gutter will be held up, and that depends on your structure:
- Free-standing carport, veranda or open lean-to (no fascia board): you need a self-support gutter. This type has a built-in support bar or bracket that fixes back to the wall or to the roof's posts, holding the gutter in place where there's no fascia to screw to. It's the standard choice for polycarbonate veranda and carport roofs.
- Roof built against a wall with a timber fascia or wall plate: you can use ordinary fascia-mounted PVC guttering on standard brackets.
If you already have self-support brackets, you're on the right track — you just need a matching gutter run and the fittings to complete it.
The bit that really matters: gutter capacity
This is where most mistakes happen. Gutters come in different profiles with very different capacities, and a roof that sheds water fast (like a smooth polycarbonate one) needs enough capacity to cope.
- Mini / 76mm gutter — only suitable for small structures: porches, small canopies and little lean-tos under roughly 25m² of roof area. Cheap and neat, but it will overflow on anything bigger.
- Half-round 112mm — fine for modest roofs.
- Deep-flow / high-capacity — the best all-round choice for most polycarbonate roofs. It carries roughly twice the water of a half-round profile, so it comfortably handles larger carports, wider lean-tos, steeper pitches and heavy-rainfall areas.
As a rule of thumb: small porch-sized roof, a mini gutter is fine; anything bigger, go deep-flow. If in doubt, size up — an overflowing gutter causes far more grief than a slightly larger one.
Downpipes: smaller than you'd think
You don't need a huge downpipe to match a deep-flow gutter. A standard 68mm round downpipe is enough, because water falls down a pipe far faster than it flows along a gutter. Plan for roughly one downpipe per 50m² of roof, and on long runs (over about 10–12m) it's better to fall the gutter from the centre to a downpipe at each end than to push everything to one corner. Finish the bottom with a downpipe shoe to throw water clear of the base.
What a complete drainage setup includes
To drain a polycarbonate roof properly you'll want:
- Gutter run — the lengths of gutter themselves (deep-flow for most roofs).
- Brackets or a self-support system — to hold it up.
- Stop ends — caps on each end so water doesn't pour out the sides.
- Running outlet — the connector that lets water drop into the downpipe.
- Union clips — to join lengths on a wider roof.
- Downpipe, downpipe brackets and a shoe — to carry water to the ground or a drain.
- Gutter sealant — for watertight joints.
uPVC is the right material
For polycarbonate roofs, uPVC guttering is the sensible choice: it's lightweight, rot-proof, maintenance-free, inexpensive and available in colours (black is the classic match). It's what virtually every polycarbonate roof kit is designed to pair with, and quality brands such as FloPlast carry long performance guarantees.
A note on pitch
Whatever gutter you choose, your roof needs a minimum 5° pitch (about 50–100mm of fall per metre) so water actually runs down to the gutter rather than sitting on the sheets. The flutes should always run downhill, from the wall side to the gutter.
Frequently asked questions
Do I need special guttering for a polycarbonate roof? No — standard uPVC rainwater guttering works perfectly. You just need the right capacity for your roof size, and a self-support type if there's no fascia.
What size gutter do I need? For a small porch or canopy under ~25m², a mini gutter is fine. For most carports, verandas and lean-tos, choose a deep-flow gutter. Larger or high-rainfall roofs should always go deep-flow.
Does EZ Glaze include guttering? No — the sheets overhang the eaves and you fit guttering separately, which lets you match it to your roof.
Can I fit it myself? Yes. uPVC guttering clips together with hand tools and is well within DIY range.
Get everything you need in one place
Planning a polycarbonate roof? Browse our (EZ Glaze polycarbonate roofing sheets) along with the (fixing screws, foam tape, wall flashing) and (gutter brackets and sealant) you need to finish the job — and get in touch if you'd like help sizing your gutter to your roof.