9mm Hollow Soffit 5m

9mm Hollow Soffit 5m

Use this hollow soffit board under the eaves with matching fascia and guttering. It is a non-load-bearing lining board — it finishes the soffit; it does not carry guttering or replace fascia.

If you want a completely smooth, unbroken face, use our 9mm plain / flat soffit board instead.

Also known as: hollow soffit, T&G soffit, tongue and groove soffit, 300mm hollow soffit, lightweight soffit, panel soffit.

Hollow soffit board vs plain soffit vs vented soffit

Important: a standard hollow soffit board does not ventilate the roof on its own. The hollow cores are for weight, not airflow into the loft. If the roof needs eaves ventilation, add circular soffit vents, a vented hollow board, or ventilate at ridge / tiles / over-fascia.

Product specification

What a 9mm Hollow Soffit board does

The soffit is the underside of the eaves. A hollow soffit board:

• closes the gap between fascia and wall
• gives a neat boarded finish under the gutter line
• keeps birds and weather out of the eaves void when fitted correctly
• can accept disc vents if you need extra airflow later

It is lighter than a solid 9mm sheet of the same coverage, which is why trade fitters often prefer a hollow soffit board on long runs and ladder work.

Where not to use it

• Not as fascia and not to carry gutter brackets
• Not as a substitute for structural boarding
• Avoid using hollow soffit as full external wall cladding in open sun and weather — it is designed as an eaves soffit. Ask us if you need a cladding product instead
• Do not treat the hollow cores as roof ventilation

Why buy a 9mm Hollow Soffit from Showcase Plastics

• Colour-matched to our fascia systems so the roofline reads as one
• Local advice on plain vs hollow vs vented before you cut
• 20+ years in roofline and building plastics
• Supply only or supply & fit
• Trade and DIY welcome
• Estimate within 24 hours
• Collection from Unit 6, Heybridge Industrial Estate, Maldon CM9 4XL, or delivery across Essex and the London borders

01621 842 000 · WhatsApp 07949 280 147 · sales@showcaseplastics.co.uk
Mon–Fri 7am–5pm · Sat 8am–12pm

Areas we supply and fit

Maldon, Heybridge, Chelmsford, Colchester, Witham, Braintree, Burnham-on-Crouch, South Woodham Ferrers, Billericay, Basildon, Rayleigh, Southend, Romford and CM, CO, SS, RM, IG postcodes.

How to install a 9mm Hollow Soffit

This is an overview, not a full method statement.

1. Check whether the roof needs eaves ventilation. If yes, plan disc vents, vented board or another air path.
2. Measure fascia-to-wall width. A 300mm hollow soffit board covers about 300mm per board (allow for the tongue). Wide eaves may need two boards side by side.
3. Fit short ways where possible — from fascia back to the wall — so each board is supported at both ends.
4. Outer edge usually sits in the fascia groove or against a soffit lip. Inner edge sits on the brick, into a wall channel / J-trim, or on a batten.
5. Push the tongue and groove together along the run. Do not force damaged tongues.
6. Support on bearers at sensible centres (often around 400–600mm) so the hollow face does not dish.
7. Fix with suitable pins or screws. Do not overdrive and crush the hollow core.
8. End-to-end joints: use a panel joint, H-section or a vented joint trim. Leave a small expansion gap (around 3mm is typical) especially on dark colours.
9. Corners and hips: mitre or use the correct trim. We stock matching bullnose / end caps for 300mm boards.
10. Wipe down. No paint.

Need it fitted? We supply and fit.