5M UPVC Hollow Soffit Boards | Porch Soffit

How to Calculate How Much Hollow Soffit You'll Need When Using Short Lengths

As the majority of our customers cut hollow soffit into short lengths that they run from rear of the fascia back to the wall, they are often unsure how to calculate how many lengths they will need. Here's how to do it. Measure the distance in millimetres from the rear of the fascia to the wall. Divide 5000 by whatever the measurement is. So for example if the measurement is 250mm, divide 5000 by 250 to get 20. That tells you that each 5m length will give you 20 short pieces.

Now, multiply 20 (or whatever your answer was) by 0.3. We do this as hollow soffit is 300mm wide, so each cut piece will take you 0.3m along the length of the soffit. So in our example, 20 x 0.3m = 6m. This means that each length of hollow soffit in this example will cover 6m when cut into short pieces. From there, simply measure the length of all of your soffit and divide that by 6 (in this example), i.e. if your total soffit length is 66m you will need to order 11 lengths (66 / 11 = 6).

Whilst there is hardly any wastage when hollow soffit is used in this way we would always suggest that you order one extra length - just in case you make a mistake!

Hollow Soffit Edge Trims

You have the choice of either a J Trim or an F Trim, depending upon how the trim itself is to be fixed. J trims, shaped like the letter J, are fixed either to the underside of the soffit bearers or they are fixed directly through the middle of the channel into the brickwork. J trims are the most commonly used edge channel for hollow soffit.

F trims, shaped like an upside down letter F, are fixed through the longest leg directly into the brickwork. All trims are 5M long. No sealant is required with these trims.

Joints and Corners

H trim is used to join lengths of hollow soffit that are run longitudinally - with the grooves running parallel to the wall. H trim is also used at the corners, with the front and back of the H trim cut into an arrow head shape to fit the corner.

If the Hollow Soffit is used on short lengths, with the grooves running back to the wall, each piece is joined to the next using the integral tongue and grooves, with H section still used to form the centre of the mitred corner.

Hollow Soffit at a glance

Manufactured by FloPlast.

300mm Wide Tongue and Groove Effect

Weather, chemical and impact resistant

Maintenance free

Class 1 Fire Rated

10 Year Guarantee

To cut hollow soffit use a fine-toothed hand saw or a jigsaw fitted with a fine blade.

To fix hollow soffit at the wall side use either a J Trim or an F Trim. J trims, shaped like the letter J, are fixed either to the underside of the soffit bearers or to a batten screwed to the brickwork. J trims are the most commonly used edge channel for hollow soffit. F trims, shaped like an upside down letter F, are fixed through the the longest leg directly into the brickwork. All trims are 5M long. No sealant is required.

To join lengths of hollow soffit that are run longitudinally - with the grooves running parallel to the wall - use an H Trim. H trim is also used at the corners, with the front and back of the H trim cut into an arrow head shape to fit the corner. When using short lengths with the grooves running back to the wall, each piece is joined to the next using the integral tongue and grooves, with H section still used to form the centre of the mitred corner.

For further information about all of our products please visit our Guides and Tips section which is packed full of helpful hints, tips and videos.