SVMAJ – Rytons Slim Vent® Major (Cavity Vent/Weep)

General Details

SVMAJ – Rytons Slim Vent Major (Cavity Vent/Weep)

  • Extra long perpend cavity ventilator for use in timber frame and traditional build.
  • Open faced to give maximum airflow and prevent clogging by paint and airborne debris.
  • Huge airflow allows fitting at the maximum 1.2m centres in Scotland and approximately every third brick to NHBC Standards, giving a cost efficient advantage.
  • Internal and external water baffles prevent water transfer and make the vent an effective weep hole for drainage.
  • Clean lines maintain the aesthetic appearance of the building.
  • May also be used for cross-cavity and underfloor ventilation.


  • 304mm L x 66mm H x 10mm W (allows a 6mm venting gap) (see image gallery above).
  • CAD drawing available by email.

Free Area:

  • 330mm² per unit.


  • Clear.


  • High impact polystyrene.


  • Installation is fast and easy as work proceeds with the Slim Vent replacing the vertical mortar joint.  If necessary Rytons Slim Vent Major may be cut to length with a fine tooth saw.  Space approximately every third brick at the top and bottom of the cavity wall to ventilate the cavity and assist in the drying out of the wall.  Lower ventilators should be placed below the dpc, unless cavity trays are used when they should be positioned above the tray.  Vertically stagger vents when placing them above and below horizontal fire stops.

Handling Information:

  • Box quantity: 25 number.
  • Box size: 32cm W x 10.5cm H x 29cm D.
  • Box weight: 2.5kg.

Reference Material:

  • NHBC Standards 6.2, External timber framed walls.  Ventilation openings should be equivalent to open brick perpends every 1.2m (i.e. 650mm² free air every 1.2m).  These openings can also provide drainage of the cavity.
  • The Building (Scotland) Regulations – Domestic, 3.10.6, Masonry outer leaf.  Where the outer leaf is a masonry construction, cavities should be vented to the outside air by installing ventilators with at least 300 mm² free opening area at 1.2 m maximum centres.  Precipitation, i.e. rain, snow and sleet, can penetrate the outer leaf of an external wall and cavities are normally drained through weep holes.  These weep holes can also provide the necessary venting.
  • Also refer to: British Standards BS 5250.

NBS Specification: