1201XL Telescopic Underfloor Vent 5-7 Courses

Adjustable ventilator to provide ventilation beneath suspended ground floors between 5-7 brick courses. With incorporated grille to prevent vermin entry.

The vertical height of the ventilator unit adjusts to suit between 5 and 7 brick courses (375mm-525mm) with a minimum cavity width of 50mm.

We have an extensive range of easy-to-fit horizontal and vertical extension accessories, that do not restrict airflow, to adapt the unit for various applications.


  • To provide ventilation below suspended ground floors.

Product Information

Telescopic underfloor vent

Free AirflowPack QuantityProduct Code

  • Telescopic and adjustable for a step of 5, 6 or 7 brick courses
  • Horizontal and vertical extension accessories available
  • Free area of 8000mm2 per unit when installed without airbrick
  • Free area of 6500mm2 per unit when installed with 1201AB airbrick
  • Equivalent area of 6170mm2 per unit when installed with 1201AB airbrick
  • Special grille included to prevent entry of vermin
  • Durable, robust and totally resistant to decay
  • Satisfies all NHBC requirements.
  • Manufactured to BS EN ISO 9001 and BS EN ISO 14001.
  • Complies with all relevant Building Regulations.
  • Meets all relevant British Standards.
  • Manufactured by injection moulding in polypropylene.
  • Available in black only in packs of 10.
  • Always use in conjunction with a Timloc airbrick.
  • The airbrick and upper front opening of the telescopic underfloor ventilator must be positioned above the finished external ground level – usually at the same level as the ground level DPC • The lower rear opening of the product must project down to the level of the underfloor void and must not be obstructed by the floor construction. A vertical extension sleeve is available to fit with this product if the standard 7 course step is not adequate.
  • Building Regulations require a free airflow below suspended ground floors of at least 1500mm2 per metre run of wall. This can be achieved by spacing the ventilators at 4m centres, however, such a wide spacing is not recommended as stagnant air pockets could form in the underfloor void. Timloc recommend a spacing of not more than 2m centres to comply with NHBC standards.
  • The NHBC recommend that underfloor ventilators are spaced at a maximum of 2m centres, with ventilators also positioned not more than 450mm from the ends of the wall.
  • As a minimum requirement, ventilators should be positioned down two opposite sides of the building so as to create a cross flow ventilation action. It is good practice to position ventilators around the full perimeter of the building, particularly with complex building designs.
  • If the underfloor void is separated by dividing walls, openings must be provided to allow a free flow of air around the underfloor void.
  • The standard ventilator will fit into a cavity wall with an external leaf of 100-102.5mm, a minimum cavity width of 50mm and across a cavity of 100mm.
  • External and internal horizontal extension sleeves are available to accommodate thicker walls or wider cavities 1201XL telescopic underfloor vent Adjustable ventilator for ground floors up to 7 brick courses incorporating vermin grille.
  • To be installed with a DPC Cavity tray and wall weeps to collect any water ingress.
  • We recommend Timloc’s IL4 and 2 weeps (Invisiweep or 1143).
  • It may be a requirement to protect with a lintel for direct loads.
  • When incorporating with a gas barrier system and adjusted to the required height, the joining sections should be sealed with proprietary tape.
  • Measure the length of each wall requiring telescopic underfloor ventilators and divide by 2m to establish the quantity required.
  • Always round up if the calculation does not work out to an exact whole number.
  • To be installed with a DPC cavity tray and wall weeps to collect any water ingress. We recommend Timloc’s IL4 and 2 weeps (Invisiweep or 1143).

F30 Accessories/sundry items for brick/block/stone walling

Clause 160 | AIR BRICK

  • To BS493, Class 1, built in as the work proceeds.
  • Manufacturer: Timloc Building Products, Timloc House, Ozone Park, Howden, East Yorkshire, DN14 7SD. T: 01405 765567, W: www.timloc. co.uk
  • Reference: 1201XL Telescopic Cranked Under Floor Vent
  • Design: Rectangular
  • Work size: Each unit 375/525mm coursing x 220mm
  • Material: Thermoplastic
  • Colour: Black
  • Optional Accessories:
    • 1203 Front Extension
    • 1204 Vertical Extension Sleeve (additional 2 brick courses)
    • 1205 Duct Adaptor (suits 110mm diameter duct – 1206 Rear Extension
  • 1201XL telescopic underfloor ventilator.
  • Matching airbrick and a range of accessories available.

Latest News