How to fix corrugated roofing sheets

Corrugated roof fixings are simple to install which makes Corrapol Corrugated Roofing sheets an ideal roofing material for a wide range of projects and installers, even those with a little DIY experience.

Understanding how to properly install corrugated roof fixings is crucial for every corrugated sheet roof as they are the most important component of the installation, after the sheets themselves. Correctly installing corrugated sheet fixings can make a big difference in the lifespan of your roof and also the durability of the roof against the weather.

There are two main types of corrugated roof fixings:

Both these types of Corrapol roof sheet fixings are designed for use with our corrugated bitumen roofing sheets; Corrapol®-BT and Awnapol Premium Corrugated Sheets.

To suit the Awnapol and Corrapol-BT Sheets, we manufacture both the Corrapol Flex Cap Screws and Roof Sheet Nails in four colours matched to the sheets: Black, Brown, Green and Red!

Corrapol-BT Corrugated Bitumen roofing sheets are one of the most cost effective roofing materials available in the market and are very easy to install making them ideal for shed roofs, lean-to roofs, and other DIY roofing projects!

Awnapol® Premium Corrugated Bitumen Sheets are a heavier duty option that are more durable and robust, making them perfect for stables, garages and more!

Flexi Cap Screws Vs Roof Sheet Nails – Which is the best corrugated roof fixing?

The below chart shows a clear comparison of the best corrugated roof fixing to use on corrugated roofing projects, depending on your budget and project type.

Product Type Pros Cons

Corrapol BT Roof Fixing Nail

Corrapol-BT Roof Sheet Nails

Budget Friendly

Simple to install

Shorter Lifespan

Not as Waterproof

Rigid Head

Corrapol-BT Flex Cap Screw

Corrapol-BT Flexi Screw Cap Fixings

 Flexi Head


Long Lasting

Stronger Fix

Easy to remove and re-tighten


Requires Drill


To summarise, Corrapol-BT Flexi Screw Cap Fixings are the best corrugated roof fixing option for any roofing project due to their stronger fixing, better longevity and superior waterproofing.

This is especially the case when using Awnapol Premium Corrugated sheets as a Premium corrugated sheet deserves a premium roof sheet fixing!

How Many Fixings Per Corrugated Sheet?

The spacing of corrugated roof fixings is an important factor to consider when purchasing the items, you need for your roof. We suggest that a roof sheet fixing is installed every corrugation peak at the top and bottom of your roof and every second corrugation peak for intermediate purlins.

Each Corrapol-BT Sheet has 10 corrugation peaks which makes it nice and easy to calculate how many fixings you will need based on your roof size and layout.

All this is entirely up to the discretion of the installer as it depends on many factors including pitch, the location, the exposure of your roof etc. However, we would suggest a minimum of twenty Corrapol® -BT fixings per sheet.

Generally, if you were using our superior Flexi Screw Cap fixings then there may be less required as they are a stronger fixing than the Roof Sheet Nails.

The key thing to remember when deciding how many fixings you’ll need is that if your roof is to last the test of time it will need to stand up to wind uplift and rain/snow loading etc (depending on location!) so it is always better to have too many rather than too little fixings

Where do Screws go on a Corrugated Roof?

Always fix corrugated roof fixings through the peaks of the sheet, not through the troughs! This is very important in maintaining the water tightness of your roof as the water tends to drain via the troughs so fixing there can cause leaks and moisture issues on your structure below.

Fixing through the peaks also is a stronger position to secure the sheets because it clamps the peaks meaning the fixing force is spread down through the troughs and so covers a wider area.

How to Fix Corrugated Roofing Sheets

Here is the full guide on how to fix corrugated roof sheets:

Equipment required to Install Corrugated Roof Fixings:

How to Fix Corrugated Roofing Sheets - Steps:

  1. Safety First – Always wear the appropriate PPE equipment
  2. Ensure your Corrapol Eaves Fillers are in place on your purlins. These are recommended on every purlin. (Top Tip: To hold the Eaves fillers in place during installation simply pin or staple them onto your frame)
  3. If you have a string line then line up the string with each purlin one by one and mark the fixing points on your sheets. This helps keep your lines of fixings parallel!
  4. Before you start fixing the first run of sheets you should install your first Corrapol Rock N Lock Gable Flashing (or Wall Flashing if against a wall). This helps keep the sheets square across the roof and is easier done before rather than after the sheets are secured! Leave the Rock n Lock on the far end uninstalled at this point. (Please Note: Corrapol Rock N Lock fixing screws are a different type of screw so please ensure the correct screw is used)
  5. Starting at one end fix the sheets, in turn, moving across the roof. To install the roof sheets fixings either:
  6.  - Use a Drill to fix the Flexi Cap Screws. Popping the caps once tightened.
  7.  - Use a Rubber Mallet to fix the Roof Sheet Nails, being careful not to overdrive them
  8. When you reach the last sheet in your run of sheets ensure you have cut the sheets to size widthways to allow for the overlap and the Rock N Lock Flashing. Follow our How to Cut Corrugated Bitumen Sheet Guide for the correct method.

For our full installation help and top tips please visit our Corrapol Installation Guide which goes through the full installation process in detail!

Does the same method apply for fixing Corrapol Clear Plastic Roofing sheets?

Corrugated Plastic Roof Sheet fixings are similar to Corrapol-BT Flexi Cap Screw fixings, however, vary on the method and installation set up so please refer to our Corrapol Installation Guide for full details.

Did you know that Corrapol Stormproof, Corrapol PVC and Corrapol GRP Sheets can be co-installed with our corrugated bitumen ranges? A great way to create a DIY rooflight!

Is there other roof sheet fixing alternatives that I can use?

There are a wide range of fixing types on the market, however, be aware that not all are suitable are corrugated sheets so best to stay with those designed specifically for use with corrugated bitumen sheets, like our Flexi Cap Screws.

To fix roofing sheets to steel and metal frames sometimes a Hook Bolt or J Bolt can be used to fit the material to the beams below by hooking over the edge of the beams.

Can you walk on corrugated bitumen sheets?

When people ask 'Can you walk on a bitumen roof' we are often worried about the risk to an installer attempting this so tend to strongly advise against it for safety reasons.

If you follow the method above and fix each sheet in order then it shouldn't be necessary to go back on the roof. However, if you do require to go onto the roof anytime just ensure you use a crawling board.

Have a question about installing corrugated roofing sheets or fixings?

Feel free to leave a comment question below and we'll respond publicly to help any other DIYers with the same question! Alternatively, chat with our product experts on our Live Chat with any unanswered questions you have! 




Unfortunately, it isn’t possible to easily secure corrugated plastic roofing sheets from the inside. You could try using a roofing bolt and securing the nut from the inside, however, this would still require access to insert the bolt from the top and hold it whilst tightening the nut. More importantly, if there is no access from above it would be hard to seal the fixing properly.

When fixing corrugated plastic, you start with the first sheets and work across widthways so the sheet could be secured by standing on the inside of the roof you are covering. Outside access is then only essential to secure the last roofing sheet.

Liz Nutt

Liz Nutt

Is it possible to fix plastic corrugated roofing sheets from the inside as we have a problem with access on the outside?

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