What are stepped cavity trays for?

Stepped cavity trays are used where a pitched roof abuts a cavity wall. To calculate the quantity of trays required to cover a section of roof abutment one of three measurements must be determined, either the vertical height or the sloping or horizontal length of the abutment.

Where should cavity trays be installed?

Cavity tray best practice

1. Cavity trays should be installed over all external door and window openings including bay windows and at roof abutments, both horizontal and pitched.
2. The cavity tray should be correctly located directly over the window/door head.

How high should a cavity tray be?

150mm
The cavity tray should fully protect the opening. A cavity tray should be provided 150mm above any adjoining roof or balcony surface. The tray should be lapped over any roof upstand or flashing to ensure water penetrating into the cavity does not enter the enclosed area.

Are cavity trays necessary on a rendered wall?

Cavity trays are required at all roof abutments. Preformed stepped cavity trays should be provided at raking abutments with a weephole at the bottom tray. A site made or preformed cavity tray should be provided at horizontal abutments with weepholes at maximum 1m centres.

Do you bed DPC on mortar?

Lay the DPC on a full even bed of fresh mortar in one continuous length, for the full width of the leaf. Provide at least a 100mm overlap at any joint or corners. The DPC must not obstruct the cavity. Ensure the external edge of the DPC is visible and not bridged by mortar when completing pointing of the mortar joint.

Can a DPC be stepped?

The DPC must be stepped in the masonry coursing so that it is never less than 150mm above the finished ground level as shown in the diagram below: Please Note: Every care was taken to ensure the information in this article was correct at the time of publication.

Does a cavity tray need weep holes?

Preformed cavity trays Whichever cavity tray construction is used, weepholes are required. At least two weepholes must be provided to cavity trays above openings and pre-formed “weeps” should always be used at maximum 900mm centres and always be positioned at stop ends.

Is a cavity tray required at DPC level?

There isnt normally a cavity tray at dpc level, unless in instances where the likes of a Radon Barrier is required, which should overlap inner wall, cavity and outer wall. You would then need a cavity tray above with weep holes.

Can DPC be above floor level?

Unlike timber suspended floors where the damp proof course will be sited below floor level with solid constructed floors the DPC should always be sited above finished floor level and should be visible.

Do you need cavity trays with rendered walls?

Do I need a cavity tray at DPC level?

Should you fill the cavity below DPC?

A clear cavity for at least 225mm below dpc should be maintained. When specialised foundations are used, including those for timber framed buildings, this depth may be reduced to 150mm below dpc if weep holes are provided and other necessary measures are taken to ensure that the cavity can drain freely.

Do you need weep holes in a cavity tray?

Whichever cavity tray construction is used, weepholes are required. At least two weepholes must be provided to cavity trays above openings and pre-formed “weeps” should always be used at maximum 900mm centres and always be positioned at stop ends.

How deep should cavity fill be?

A minimum 225mm clear cavity below the DPC should be maintained. When specialised foundations are used, including those for timber framed buildings, the minimum clear cavity depth may be reduced to 150mm below the DPC, provided that weep holes and other necessary measures are taken to ensure free drainage.

What are the general fitting instructions for stepped cavity trays?

Manthorpe Building Products Product Information Sheet TITLE GENERAL FITTING INSTRUCTIONS FOR STEPPED CAVITY TRAYS CODE THE CORNER OF THE TRAY SHOULD BE 75mm OFF FINISHED ROOFLINE APEX TRAY A dummy truss should be positioned at roof abutment 75mm off the finished roof line as shown.

Where is the catchment tray on a roof?

The Catchment Tray is located at the lowest point of the abutment and is generally the first tray to be fitted. This tray should be mortared into position with the corner 75mm off the finished roof line and if possible over the gutter. To achieve this it is normally necessary to cut bricks.

Do not fit a dry bed tray to a G950 vent?

DO NOT FORGET TO FIT A G950 WEEP VENT DO NOT DRY BED TRAYS After fitting the tray and mortar is dry lead should be fitted as shown, this should be easily done if the tray has been positioned correctly. If there is a gutter under the tray then the lead should be dressed into it as shown.