Building Ventilation

At Sydenhams we offer a range of underfloor and through the wall building ventilation products from Manthorpe.
Manthorpe Logo

Telescopic Underfloor Vents

The telescopic underfloor vents provide an airflow passage through the wall into the voids below suspended concrete and timber floors. The telescopic feature enables the product to adjust the ventilation channel vertically within the cavity, helping to meet the Building Regulations Part C requirement for ventilated floors.

G960 Telescopic Underfloor Vents

Designed to provide a clear airflow passage to the void underneath a suspended floor. The telescopic feature enables the ventilator to adjust vertically between three and five brick courses. The right airflow can be achieved when the ventilator is used with a Manthorpe G930 Airbrick.

The aperture can also accept a standard clay airbrick, although the airflow is reduced.

Key Features

  • 6,600mm² airflow
  • Allows ventilation to an underfloor void
  • Allows a 3-5 course stagger
  • Additional depth and cavity span available with extension sleeve

G965 Dual Extended Underfloor Vent

Designed to provide a clear airflow passage to a void beneath an insulated suspended floor. The G965 offers a vertical telescopic adjustment of between 5 and 8 brick courses without the need for an extension sleeve. The horizontal outlet is long enough to bridge through an overall wall thickness of 350mm without the need for an additional extension.

The front aperture of the G965 is designed for use with a G930 Combination Airbrick or it can be used in conjunction with a traditional clay airbrick, although this would reduce the overall airflow through the system.

Key Features

  • 8,000mm² airflow
  • Allows ventilation to an insulated underfloor void
  • Allows a vertical extension of 5-8 courses (318mm-575mm)
  • Allows a horizontal span of 360mm (including G930)

G961 Extension Sleeve

Designed for use with the Manthorpe Telescopic Underfloor Ventilator (G960). Each extension sleeve allows the vent to reach a further two brick courses vertically. The sleeve can also be fitted to the base of the G960 to provide horizontal extension through larger cavities.

Key Features

  • 6,600mm² airflow
  • Allows ventilation to an underfloor void
  • Additional depth and cavity span
  • Allows a 3-5 course stagger + 2 courses per unit

Weep Vents

Designed for discreet cavity wall drainage and ventilation requirements. The Manthorpe range of weep vents can be used to drain DPCs, cavity trays and lintels along with providing airflow circulation to timber frame cavity walls.

G950 Weep Vent

The Manthorpe G950 Weep Vent is used to drain lintels, cavity trays and to ventilate cavity walls.

The product can be slotted between two bricks and mortared into position. It provides an unobtrusive ventilation point for the cavity behind.

The vent has a baffled grille to prevent the ingress of driving rain and wind whilst incorporating an insect grille and drip lip. This grille is sized to keep out large insects but is wide enough that it will not be blocked by debris, paint or water droplets.

When used with the Manthorpe range of catchment trays the Weep Vent should be placed in the furthest corner away from the finished roof line.

The Weep Vent should be spaced at no greater than 900mm centres to meet N.H.B.C guidelines, which state, “weep holes are recommended to be sited at every 450mm maximum with at least two per opening above all windows and doors.”

Key Features

  • Provides 220mm² ventilation airflow
  • Replaces a single mortar joint
  • Available in a variety of colours

G951 Peep Weep

Provides an unobtrusive solution to cavity wall drainage requirements. The weep features a mortar key to ensure adhesion to the building fabric and an external rib to aid positioning.

The rib surrounds a 62mm high opening to prevent mortar blockage from within the cavity. The weep’s protective hood which when fitted “peeps” out from the brick fascia is designed to guard against blockage during installation and stops penetration of wind driven rain. The exit hole is ample for water drainage but small enough to prevent entry of large insects.

Key Features

  • Drains lintels and cavity trays
  • Replaces a single mortar joint
  • Offers a discreet drainage option
  • Available in a variety of colours

G930 Airbrick

Designed to provide high levels of ventilation into cavity walls and underfloor voids. Can be stacked to create 9x6 & 9x9 airbricks.

The brick incorporates a front mounted grille with water deflectors while a mortar key around the edge of the airbrick ensures it can be securely fixed to the building fabric. This product is suitable for use with gas appliances.

Key Features

  • 6,450mm² of airflow per 9 x 3 airbric
  • Can be stacked together to create 9 x 6 and 9 x 9 combination
  • Moulded in mortar key
  • Available in various colours to suit different substrates



Blue Black



G935 Cavity Sleeve

The G935 Combination Cavity Sleeve fits into the back of Manthorpe’s G930 Airbrick to ventilate through a standard cavity or solid brick wall. The unit can be stacked to create a 9 x 6 and 9 x 9 alternative, and telescopes to fit cavity widths of 50mm to 100mm, with further extension possible through the addition of extra product units.

The G935 also includes an integral wind baffle.

Key features

  • Can be slotted and telescoped onto itself
  • Will work with the G930 when stacked in 9 x 6 and 9 x 9 combinations
  • Integral wind baffle
  • Will also act as an extension to the G960

G962 Remote Void Vent

The G962 Remote Void Ventilator is designed to connect the G930 Air Brick or G960 Underfloor Vent to a 4” Round Pipe or alternatively Manthorpe’s GRPA/1 Flexible Pipe.

The adapter fits directly onto the bottom of the G960 Under floor Vent and can be easily cut down between the pre moulded cut lines to fit the G930 Airbrick.

Key Features

  • 8,800mm² of airflow
  • Works with G930 and G960
  • Sleeves onto 4” round pipe or Manthorpe’s GRPA/1 Flexipipe