Soffit fitting guide

How to fit a soffit

A correctly fitted fascia installation goes hand-in-hand with a properly fixed soffit.  Successful installation of each will deliver superb aesthetic results, together with a weatherproof, breathable roofline, capable of performing for many years to come.

As with fascia installation its best to use the services of an experienced professional when fitting a soffit to your roofline – even so, understanding the installation process can give you a background knowledge that’s useful to have under your belt.

The basic essentials

Firstly, it’s important to ensure that before beginning to fix a soffit, any preservative treatment used on your roofs structural timbers has completely dried out and the fascia has been fitted correctly. 

Soffit fixings

How far apart should soffit boards be fixed?

Ideally, soffit boards should be fixed using a maximum 600mm centres (or 300mm if the soffit boards are foiled).  Two fixings should be used at each centre and be positioned 20cm apart.

How should the soffit be positioned?

It’s important to ensure that the soffit is well positioned into the fascia rebate.  As a guide, all our fascia boards have a 26mm deep rebate, with the exception of our bullnosed board, which has an 18mm rebate.  We recommend fitting soffit boards to the full depth of the rebate, remembering to leave a 5mm expansion gap at the wall side and into the edge trim.

Soffit cutting sizes vary from brand to brand - so these are our cutting size recommendations:

Soffit width = opening size + 4mm (18mm bullnosed board)
Soffit width = opening size + 21mm (all other fascias)

Soffit jointing

Can multipurpose boards be used as a soffit?

Yes, multipurpose boards can be used to create a soffit, and the following information should help with the installation process:

To form corner returns, cut the soffit at the required angle and join with a centre trim (see Ref 108), but remember to leave a 5mm expansion gap at the end of each board, (or 8mm if the soffit is foiled).

Multi-purpose boards can be joined with a centre trim, however hollow soffits are better joined using an H section.

Stagger your joints, and use a minimum of 1 fixing centre between each on adjacent soffit boards, then a minimum of 2 fixings between joints, and the end of the board – and don’t forget the 5mm expansion gap (or 8mm if foiled).

Finally, as a guide, we recommend installing boards from the fascia first and working towards the house.