How To Install Top Wall Flashing on Polycarbonate Roof

After this article, you’ll be able to do what a lot of people can’t – properly install a wall flashing on a polycarbonate roof.

Installing a polycarbonate roof is often the fastest way to create a dry covered area with a clear roof outdoors. Whether for a canopy over a patio or lean-to over an outdoor cooking area, polycarbonate sheets offer a quick, easy and affordable roofing solution.

However, to create a long-lasting and waterproof roof, it is essential to understand how to seal your roof against any back, top or side walls. Installing a Polycarbonate roof flashing is the last step in the installation process but arguably one of the most critical steps to ensure your roofing sheets last.

In this guide and video, we will explain how to install roof flashing against a wall for a watertight finish. Traditionally you would have used flashing tape for polycarbonate roofing, but this can be tricky to do effectively. Flashing tape can be hard to adhere to all surfaces – particularly when walls are dirty or dusty. Additionally, it is hard to ever seal fully around the top of your roof, the ups and downs of the glazing bars or fixings, without leaving gaps or creating a crinkled messy looking finish.

Any gaps left by a wall flashing can significantly affect the roof’s lifespan. Primarily, by causing rotting or damage to the timbers and roof structure below. Any water leakage below can also affect surfaces under the roof, such as making furnishings damp or causing mould on the back wall.

Since the release of the Top Wall Flashing, these flashing challenges have been eliminated. This superior wall flashing comes with a whole host of benefits, for example, it can last 10 years more than flashing tape which degrades faster over time. Below is a list of the top benefits of using a Top Wall Flashing:

Benefits of using a Top Wall Flashing

  1. Manufactured from aluminium for Durability – 20 Years+ Life Expectancy
  2. Screw/bolt fix for strength – a mechanical provides a secure fix and removes reliance on an adhesive.
  3. Unique Foam Gasket for sealing over the roof – The Top wall Flashing Foam Gasket can be compressed or notched out to fit your roof exactly.
  4. Multiple angle options - Snapa® and Alukap® Top Wall Flashings can be installed on a wide range of roof pitches when flashing roof to wall so suits all Lean-to and canopy projects. There are two angles for fixing.
  5. Coloured Matched – Get rid of the ugly grey flashing and colour-match the flashing to your glazing bars.

In summary, it goes without saying that installing a Top Wall Flashing is a no-brainer, given the costs aren’t too dissimilar but the advantages are significant. Now, to learn how to install the wall flashing onto a polycarbonate roof this is the method:

Tool required to install Top Wall Flashing:

  • Appropriate Safety Gear
  • Hacksaw or Chop saw (with metal blade)
  • Drill with an HSS Drill bit
  • Tape Measure
  • Marker pen
  • Wall Fixings (select suitable stainless fixings to work with your wall substrate)
  • Securbond® Silicone or Flashing Tape

How to install Top Wall Flashing - Steps:

  1. Safety first – always wear the appropriate PPE equipment.
  2. Measure the roof width (from side to side) and mark this length onto the wall flashing with a pen
  3. Cut the Top Wall flashing to size with a hacksaw or chop saw. Ensure you are using a blade that is suitable for cutting metal.
  4. Slide the foam gasket onto the gasket channel and trim it to match the flashing length. This can be done easily with a saw or sharp knife.
  5. Optional step - mark on the foam gasket where each glazing bar meets flashing and cut out a small notch at each mark so that the gasket sits completely snug to the Axiome Polycarbonate sheets. This step is more likely to be required when using Snapa bars, rather than Alukap Bars.
  6. Predrill fixing holes into the flashing at regular intervals using a drill with an HSS or Metal compatible Drill Bit. There are two fixing guidelines to choose from depending on the pitch of the roof. The regularity of fixing required will depend on the wall substrate you are fixing to.
  7. Pull the Polycarbonate sheets protective film back enough to clear the foam gasket, approximately 100mm.
  8. Put the flashing in place and push down to compress the gasket onto the sheets slightly. Then fix to the wall using suitable stainless-steel fixings. The fixings shown are illustrative only.
  9. Once secured, seal the top lip with Securbond Flashing Tape or Securbond Silicone to create a weather-tight seal
  10. Finally, pull off the remaining protective film on the glazing bars and roof sheets

Use this same method for all our polycarbonate sheets whether you are installing twinwall polycarbonate with our Snapa PVC Glazing bars or our solid polycarbonate sheets with the Self Supporting Glazing bars.

We manufacture 3 versions of the Top Wall Flashing at Clear Amber including the:

  • Snapa Top Wall Flashing
  • Alukap-XR Top Wall Flashing
  • Alukap-SS Top Wall Flashing

We also manufacture a corrugated wall flashing for use with bitumen roof sheets and clear corrugated roofing sheets. It is designed with the same unique features for a durable and fast installation on corrugated roofs.

Common Polycarbonate Roof Flashing Questions:

Why is a top wall flashing better than a lead roof flashing?

Installing a lead roof flashing is a complicated process, even for experienced professionals, as it requires cutting the lead properly into your brickwork and fixing back in the cuts. In turn, installing lead roof flashing is very time consuming so by using a Top Wall Flashing you can more than half your installation time.

Finally, the style of lead flashing is quite old school and plain with its dull grey colour so a Top Wall Flashing offers a colour matched flashing option that looks better overall.

What colours is the Top Wall Flashing available in?

Top wall flashing is manufactured in white, brown and bespoke powder-coated options. The Snapa Top wall flashing is only white to match the white pvc glazing bars, however, with the Alukap Top Wal Flashing you also get Dark Brown and bespoke coloured. Bespoke Powder coating literally means you can choose any colour you wish! People often like to match their houses, for example, traffic blue to match their door colour.

What colour Roof Flashing should I use?

The majority of people match their roof flashing to their Glazing Bars colour to keep the colour scheme consistent. The most popular colour is a white roof flashing.

Alternatively, you could match the Top wall flashing to your wall and use a contrasting colour. For example, bespoke Agate Grey or Cream.

Why are stainless steel fixings used on the Top Wall Flashing?

If possible, it is best to use stainless steel fixings to prevent the steel in the fixings from reacting with the aliment in the Snapa Top Wall flashing. This is the same no matter whether you are using bolts or anchors or any other type of fixing.

Always purchase fixings that are suitable for your wall substrate. If you are unsure what fixings to use, please contact a fixings manufacturer.

Does this roof flashing work with twinwall polycarbonate, solid glazing and glass?

Yes, the Top Wall Flashing can be used on any type of glazing material – polycarbonate or glass.

Need Help with Roof Flashing on your Polycarbonate Project?

If you are needing help with your Roof Flashing projects then please do not hesitate to contact us. Our Team will be happy to assist on our Live Chat or email where our we can provide you with all the advice and support you require.

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