

Telescopic Underfloor Vertical Vent Extension Piece
Adjustable vertical vent extension for underfloor applications. Designed to extend vent reach both horizontally and vertically. Accommodates various wall, cavity, and brick course layouts.
Nationwide Delivery
Thu 13 Nov
- 2days
- 15hrs
- 3mins
- 26secs
Product Overview
Adjustable vertical vent extension for underfloor applications. Designed to extend vent reach both horizontally and vertically. Accommodates various wall, cavity, and brick course layouts.
Delivery & Returns Information
How Our Delivery Works
We work with a nationwide network of trusted suppliers. As a result, items in your basket may be supplied by different suppliers and delivered separately. Where this applies, you'll see multiple delivery charges at checkout. We always aim to group products from the same supplier to keep delivery costs as low as possible.
Delivery Areas & Charges
Delivery charges listed on our website apply to mainland UK, excluding the following postcode areas: AB, CF, DD, DG, EH, FK, KA, KW, KY, IV, LA, LD, LL, ML, NP, PA, PH, SA, SY & TD
If your delivery address falls within one of these postcode areas, we’ll be in touch before processing your order to confirm any additional delivery costs.
Please note: We do not currently offer delivery outside the UK mainland.
Standard (Nationwide) Delivery
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Core Products Core
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| ORDER VALUE | DELIVERY CHARGE |
| Under £300 ex. VAT | £20 ex. VAT |
| Over £300 ex. VAT | FREE |
Core Delivery charges apply only when all products in an order that have equivalents are accepted as such. If even one product cannot be substituted with an equivalent, the entire order will not qualify for Core Delivery charges.
| Timber & Sheet, Building Materials, Joinery and Gardens & Landscaping Products | |
|---|---|
| ORDER VALUE | DELIVERY CHARGE |
| Under £100 | £20 ex. VAT |
| Between £100 - £300 ex. VAT | £10 ex. VAT |
| Over £300 ex. VAT | FREE |
| Insulation, Plasterboard and Drylining Products | |
| ORDER VALUE | DELIVERY CHARGE |
| Under £350 | £35 ex. VAT |
| Over £350 ex. VAT | FREE |
| Screws & Fixings and Adhesives & Sealants | |
| ORDER VALUE | DELIVERY CHARGE |
| Under £50 | £5 ex. VAT |
| Over £50 ex. VAT | FREE |
Express Delivery
| Express Delivery - Insulation and Plasterboard & Drylining | |
|---|---|
| ORDER VALUE | DELIVERY CHARGE |
| Under £400 | £50 ex. VAT |
| Over £400 ex. VAT | £35 ex. VAT |
| Express Delivery - Timber & Sheet, Building Materials, Joinery and Gardens & Landscaping Products | |
| ORDER VALUE | DELIVERY CHARGE |
| Under £300 | £50 ex. VAT |
| Over £300 ex. VAT | £35 ex. VAT |
Returns
We offer a 30 day returns policy on any faulty products.
Key Features
- {{open_in_full}} Extends vent to deeper voids
- {{air}} Ensures effective sub-floor airflow
- {{fitness_center}} Robust build for lasting performance
- {{check_circle}} Simplifies deep void vent installs
Technical Specification
| Sales Unit: | Each |
|---|---|
| Colour: | Black |
Product Overview
Telescopic Underfloor Vertical Vent Extension Piece designed to extend the vertical reach of a primary telescopic underfloor ventilator system.
This modular component connects directly to the main vent body, increasing the effective depth between the external air brick and the sub-floor void. Manufactured from UV-stabilised, weather-resistant polypropylene, it delivers long-term durability in damp or below-ground conditions.
By maintaining a continuous and unobstructed air pathway, it ensures that fresh air is drawn in and moisture-laden air is expelled efficiently, even where deeper foundations or irregular ground levels exist.
Features & Benefits
- Increased Vertical Adjustment: Extends the reach of the main underfloor vent to accommodate deeper foundations and varying ground levels.
- Secure System Integration: Precision-engineered to connect seamlessly with compatible telescopic underfloor vent units, maintaining full airflow continuity.
- Durable and UV-Stabilised Construction: Manufactured from high-impact polypropylene resistant to decay, moisture, and soil chemicals for long service life.
- Preserved Airflow Efficiency: Maintains a clear, continuous ventilation path from the external air brick to the sub-floor void without obstruction.
- Simplified Installation Process: Enables straightforward adjustment on-site, reducing the need for bespoke ducting or complex assemblies.
- Cost-Effective Adaptability: Provides an economical method to extend standard ventilation systems to suit non-standard depths.
- Regulatory Support: Assists compliance with UK Building Regulations, including Approved Document C (moisture control) and Approved Document F (ventilation).
Applications
- Sub-Floor Ventilation Extension: Extends the vertical depth of telescopic or periscope vent systems to reach lower sub-floor voids.
- Deep Foundation Adaptation: Suitable where air brick positions are above standard height due to stepped or sloping ground.
- New Build Installations: Used during construction to achieve compliant underfloor ventilation in varying foundation designs.
- Refurbishment Projects: Allows adaptation of existing ventilation systems to meet modern standards or altered floor levels.
- Moisture Management: Ensures adequate airflow to prevent damp, condensation, and timber decay in underfloor spaces.
Installation Guidance
- Connection to Vent Unit: Attach securely to the primary telescopic underfloor vent body, ensuring a tight fit to maintain airflow.
- Height Adjustment: Stack one or more extension pieces as required to achieve the desired vertical depth between air brick and void.
- Alignment: Ensure alignment is maintained to prevent air restriction and preserve clear ducting.
- Securing in Place: Fix or stabilise components as recommended by the vent manufacturer to resist movement during backfilling or finishing.
- System Verification: Check that the assembled vent path remains unobstructed and correctly positioned before completing external works.
Compliance & Performance
- Material Specification: Manufactured from UV-stabilised, weather- and impact-resistant polypropylene.
- Performance Role: Extends vertical airflow path without reducing effective ventilation capacity.
- Compatibility: Designed for direct connection to standard telescopic or periscope underfloor vent systems.
- Durability: Resistant to decay, moisture, and temperature fluctuations typical of below-ground environments.
- Regulatory Alignment: Supports compliance with Building Regulations Approved Documents C and F for underfloor moisture and ventilation control.
- Important Note: Extension pieces must always be used in conjunction with a compatible primary telescopic vent unit; do not install as a standalone component.