Structural Glazing Bars

We offer a wide range of structural glazing bars that, whilst primarily designed for glazing with multiwall polycarbonate, are also regularly used for installing glass, either single panes or 24mm double-glazed units.

A structural bar is designed to free-span from the ridge down to the eaves on a sloping roof. The table below shows our range of structural bars and the spanning capacity of each one. If your roof is longer than these recommended spans a cross member or purlin should be added to provide additional support for the bars.

 Maximum span with:
Bar SystemMultiwall polycarbonate6.8mm Laminated Glass24mm glass unit
P2271.4mnot testednot tested
P2861.5mnot testednot tested
P2884mnot suitable2.6m
P288GC4mnot testednot suitable
P600 Snap Fit3m or 4m*not suitablenot suitable
 *3m span using 16mm or 25mm multiwall glazing at 1m centres
 4m span using 16mm or 25mm multiwall glazing at 600mm centres

Please note that the multiwall spans noted above are based on 16mm or 25mm multiwall polycarbonate. The information regarding glass is based on maximum 600mm glazing centres. Whilst the push-fit plastic end plate that we supply with our bar packs is satisfactory for using with multiwall glazing a mechanically fixed end plate should always be used with our bars when installing glass. Details of these are on our Glazing Accessories page. All of our bar systems should be installed at a minimum 5 degree pitch – any less and you may get water ingress.

Twinfix was the first company in Europe to offer glazing bars that were specifically designed for installing multiwall polycarbonate glazing sheets. Traditional glazing bars used for glass do not have a wide enough edge engagement to hold this relatively flexible, but incredibly tough, glazing medium, hence the need for a different design of bar. Over the years we have continued to develop our range of polycarbonate glazing bars and now offer an extremely wide selection of systems.

All of our structural bar systems are around 60mm wide and the majority of them are manufactured in aluminium with a screw-down capping bar to create an extremely secure roof. One of them features a hidden fixing system to the capping bars (the P286). Our aluminium glazing bars and complementary fixing accessories are offered powder coated in either white or brown as standard items and mill finish is also usually available. For a minimum quantity order you can select other colours, although this might involve a price premium and also require a slightly longer lead time.

When it comes to installing our bars we recommend that you use stainless steel screws. Other types of metal screw could cause a metallurgic reaction between the aluminium bars and the screw substrate which may result in a future failure. Similarly, if you are mounting our aluminium bars on to a steel frame it is advisable to insert a suitable membrane barrier between the two surfaces.

Aluminium is a great material for use in this application as it is strong, but light in weight. It doesn’t rust in use and once powder coated it will not need re-painting in the future. Add to this the fact that you can recycle it when your roof is no longer required and you can see that this is a very nice, green product.

Help & Advice

If you have a project in mind or would like help or advice on any of our products or services, please either ring us on 01925 811311, email us at or get in touch via the enquiry form on our Contact Us page.


Related FAQs

1. Can I use your glazing bars to install glass?
You can use all of our bars to install glass, with the exception of the P600 and P700 Snap-fit systems. However, please note that you will need to use a Mechanical End Plate to ensure the glass is held securely in place; the plastic end plates that are supplied with the bars are only suitable for use with multiwall polycarbonate.