Best PVC Roofing Screws for Secure Outbuilding Roof Fixings — UK Buyer’s Guide 2026
- Best overall: Self Drilling Screws for Heavy Section — The 5.5 x 65mm size, 16mm washer, and Ruspert plating with 500+ hours salt spray resistanc
- Runner-up: 4.8mm x 35mm Anthracite Grey Self-Drilling Roofing Screws Farmer — The 4.8 x 35mm size with EPDM sealing washers and RAL 7016 anthracite finish suits neat ro
- Third choice: 4.8mm x 50mm Self Drilling Countersunk Screws Steel Self — The 4.8mm diameter and 50mm length give a useful middle-ground size, with drilling capacit
Roof fixings fail for boring reasons: the wrong screw length, poor corrosion resistance, or a washer that never seals properly. On an outbuilding roof, that means leaks, lifted sheets, and fasteners that back out after wind and weather.
This guide compares real screws with real specifications so you can choose the right fixings for PVC roofing, timber support, and mixed roof jobs. It is for UK DIYers and trade buyers who want straightforward recommendations based on size, coating, washer type, and drilling capacity rather than vague marketing.
| Product | Price | Size | Color | |
|---|---|---|---|---|
| Self Drilling Screws for Heavy Section 🥇 Top Pick |
£10-£20 | 5.5 x 65mm with 16mm Washer | Silver | Check price |
| 4.8mm x 35mm Anthracite Grey Self-Drilling Roofing Screws Farmer 🥈 Runner-Up |
Under £10 | 4.8mm x 35mm | Anthracite Grey | Check price |
| 4.8mm x 50mm Self Drilling Countersunk Screws Steel Self 🥉 Third Place |
— | 4.8mm x 50mm | Silver | Check price |
| ForgeFix Single Thread Screws 4th |
Under £10 | 5.0 x 80mm | Zinc | Check price |
Specifications from Amazon product data. Price bands are a rough guide only — check the current price on Amazon before buying.
What to Look For — Buyer’s Guide
What to Look For
For PVC roofing and outbuilding sheets, the first thing to check is whether the screw has a proper sealing washer. EPDM is the key material to look for because it compresses against the sheet and helps keep water out. A larger washer can also help spread load; for example, the top pick uses a 16mm washer, which is more reassuring than a bare countersunk head.
Next, match the length to the job. A 4.8 x 35mm fixing is better for lighter sheet work, while a 5.5 x 65mm screw gives much more reach for heavier sections. Corrosion resistance matters too, especially on exposed outbuildings. If a product gives you a concrete figure such as 500+ hours salt spray resistance, that is more useful than a vague claim. Finally, check the drilling capacity or self-drilling range if you are going into steel or mixed material.
How Much Should You Spend?
You do not need to chase the highest spec for every job. For small, neat roof fixing jobs, a simpler 4.8mm self-drilling screw with EPDM washers can be perfectly adequate. Spend more when you need a larger washer, a longer screw, or proven corrosion resistance for harsher exposure. The best value usually comes from buying the right specification first, not the biggest pack or the shiniest coating.
Our Top Picks
£10-£20
Self Drilling Screws for Heavy Section
“The 5.5 x 65mm size, 16mm washer, and Ruspert plating with 500+ hours salt spray resistance make it the strongest all-round roof fixing here.”
This is the most capable option in the group if you want a screw that can cope with heavier roofing work. The 5.5 x 65mm size gives it more reach than the shorter fixings here, and the fixed washer is 16mm, backed by galvanised steel EPDM for sealing. The Ruspert coating is the standout detail: 500+ hours of salt spray resistance, with UKAS accreditation, is a proper spec rather than vague corrosion talk.
The trade-off is that it is a more specialised, heavy-duty fixing than a simple general-purpose screw. Its 8mm head and drill point 12 suggest it is built for demanding installation, but that also means it is not the neatest choice for lighter PVC sheets or small jobs where a shorter screw would be less intrusive. If you need maximum security and weather resistance, though, this is the one to beat.
- 5.5 x 65mm size gives strong reach for heavier fixings
- 16mm fixed washer with galvanised steel EPDM for sealing
- Ruspert finish with 500+ hours salt spray resistance
- More screw than you need for lightweight roofing jobs
- Heavier-duty design is less suited to small, discreet fixings
Best for: Buyers fixing heavier outbuilding roof sections who want the best corrosion resistance and a larger sealing washer
💬 Verdict: Best overall if you want the most robust, weather-resistant roof fixing in this list.
Under £10
4.8mm x 35mm Anthracite Grey Self-Drilling Roofing Screws Farmer
“The 4.8 x 35mm size with EPDM sealing washers and RAL 7016 anthracite finish suits neat roof-sheet fixing where appearance matters.”
This is the cleanest-looking option here, and the 4.8 x 35mm size makes it a sensible match for lighter roofing work where you do not want an overlong screw showing through. The self-drilling tip keeps installation simple, while the EPDM sealing washers are the key practical feature for keeping water out.
Its main weakness is that the product data is thin compared with the top pick: there is no stated coating performance figure, and the pack size is only given as 50. It is a good fit for colour-matched roofing in RAL 7016, but it is not the most obviously heavy-duty screw in the lineup. Choose it for appearance and tidy fixing rather than maximum toughness.
- 4.8 x 35mm size is well suited to lighter roof-sheet fixing
- EPDM sealing washers help with weatherproofing
- RAL 7016 anthracite grey finish blends with modern roof sheets
- No corrosion-resistance figure is provided
- Shorter 35mm length is not ideal for thicker or heavier sections
Best for: Anyone wanting a discreet, colour-matched fixing for anthracite roof sheets and lighter outbuilding roofs
💬 Verdict: Best runner-up for neat-looking roofing where the finish matters as much as the fixing.
—
4.8mm x 50mm Self Drilling Countersunk Screws Steel Self
“The 4.8mm diameter and 50mm length give a useful middle-ground size, with drilling capacity from 1.75mm up to 4.4mm.”
This is a sensible, straightforward self-drilling screw with a useful middle-ground size. At 4.8mm x 50mm, it sits between the shorter roofing fixings and the heavier 65mm option, so it should suit a lot of general fixing jobs where you want a bit more reach. The stated drilling capacity from 1.75mm up to 4.4mm is helpful because it tells you exactly what material thickness it is intended to handle.
The weakness is that it is the least specialised roofing screw here. It is zinc plated, but there is no washer spec listed, which matters if you are relying on the fastener itself to seal a roof fixing. The countersunk head may suit some applications, but for roofing work with PVC sheets you would usually want a clearer sealing solution. Useful, but not my first choice for outbuilding roof fixings.
- 4.8mm x 50mm is a practical middle-ground size
- Drilling capacity from 1.75mm to 4.4mm is clearly stated
- Zinc plated steel keeps the spec simple
- No washer specification is given
- Less obviously suited to weather-sealed roofing than the dedicated roofing screws
Best for: Buyers who need a general self-drilling screw for mixed light-duty fixing work rather than a dedicated roofing fastener
💬 Verdict: A decent general-purpose option, but not the best choice if your main job is sealing a roof.
Under £10
ForgeFix Single Thread Screws
“The 5.0 x 80mm size and aggressive single-thread design give strong holding power in timber, with a flush countersunk head for a clean finish.”
This is a timber screw, not a roofing screw, but it can still have a place in outbuilding work where the roof structure needs fastening rather than the sheet itself. The 5.0 x 80mm size gives plenty of length, and the aggressive single-thread pattern is designed for high pull-out resistance in softwoods, hardwoods, and chipboard. The flush double-countersunk head is another useful detail if you want a neat finish.
Its drawback is that it is simply the wrong tool for sealing PVC roofing sheets. There is no washer, no roofing-specific sealing detail, and nothing here that suggests weatherproof sheet fixing. The yellow passivated coating is corrosion-aware, but this is still better viewed as a structural or timber screw than a roof sheet fastener. Good product, wrong primary job.
- 5.0 x 80mm size gives strong timber engagement
- Single-thread design improves pull-out resistance
- Flush countersunk head gives a tidy finish
- No EPDM or roofing washer
- Not designed as a sheet-sealing roof fixing
Best for: Buyers needing a strong timber screw for the roof structure rather than the roof covering itself
💬 Verdict: Useful for timber work, but not the best match for PVC roofing fixings.
Our Verdict
Our top pick is Self Drilling Screws for Heavy Section because the 5.5 x 65mm size, 16mm washer, and 500+ hours salt spray resistance make it the strongest all-round choice for secure outbuilding roof fixings. The runner-up is 4.8mm x 35mm Anthracite Grey Self-Drilling Roofing Screws Farmer, which suits buyers who want a neater, colour-matched fixing for lighter roofing work.
If you need maximum durability and weather resistance, choose the top pick. If you want a tidier finish and a shorter fixing for lighter sheets, the runner-up is the better fit.
What we would skip: generic countersunk wood screws without EPDM washers. They may drive in cleanly, but they are not a proper roofing fixing, so they are a poor choice if you want a weather-sealed, long-lasting roof repair.
Frequently Asked Questions
What size screws should I use for PVC roofing sheets?
For lighter sheet work, a 4.8 x 35mm screw is a sensible starting point. For heavier or thicker sections, a 5.5 x 65mm fixing gives more reach and support.
Do roofing screws need EPDM washers?
Yes, if you want a proper weather seal. EPDM washers compress against the sheet and help reduce the risk of leaks around the fixing point.
What does self-drilling mean on roofing screws?
It means the screw has a drilling tip that can start its own hole, which makes installation easier and can remove the need for a separate pilot drill in suitable materials.
Is a countersunk screw suitable for roof sheets?
Not usually on its own. A countersunk head can sit neatly in some materials, but for roofing you normally want a screw with a sealing washer so the fixing is weatherproof.
What corrosion resistance should I look for on outbuilding roof fixings?
Look for a clear coating spec rather than a vague claim. A stated figure such as 500+ hours salt spray resistance is a strong sign the screw is built for exposed conditions.
