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Drainage Tray Details

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Product Information



1    The Drainage Tray comprises four components; a sill tray, two end sections (left and right handed), and support wedges. The sill tray is an extruded uPVC profile approximately 96 mm wide, which is cut to length to suit the window opening. It has a slope of approximately 4° and at the rear a 14 mm upstand section, which is used to support the window. The end sections fit into and form a side upstand at the bottom comers of the framing opening, and are attached to the ends of the tray. The PVC support wedges fit on top of the sill tray to provide extra support to larger or heavier double glazed window or door units. All components are coloured white.

2     A watertight seal between the tray and end sections is provided by PVC cement.

3   The Drainage Tray is fixed to the framing through the end section upstands with either plasterboard clouts or screws.

4   The tray is suitable for use with nominal 100 mm, or greater width, framed walls.


Handling and Storage                                                         Top

Care must be taken to ensure that The Drainage Tray components are not damaged before or during installation.


Design Information                                           Top


1    The Drainage Tray is designed to fit directly under aluminium joinery to divert water to the building exterior. Water sources include leaking joinery, failed jamb seals or flashings, condensation or wind-driven rain. The Drainage Tray is not designed to overcome poor detailing and workmanship of window installation, nor is it a replacement for seals or flashings at jambs, and flashings at heads and sills, but is for use in [ conjunction with these items.

2   Jamb flashings must extend and lap over the end sections of The Drainage Tray.

Service Life                                                                         Top

The Drainage Tray is expected to have a service life similar to that of the window to which it is fitted.

Maintenance                                                                       Top

No maintenance can be carried out on The Drainage Tray, as it is inaccessible once the joinery is installed. The gap between The Drainage Tray and the bottom flange of the window or door frame must be kept clear of wind-blown debris, cobwebs and the like to ensure that water can drain freely to the exterior.

External Moisture                                                               Top

1   The Drainage Tray is suitable for use in all Building Wind Zones of NZS 3604, up to, and including Very High.

2   Sills onto which The Drainage Tray discharges must be sloped toward the building exterior at a minimum

3   Where the Building Wind Zone exceeds Medium, an air-seal must be provided around the joinery, with the following method being suitable.  eg. Compressible foam strip or expanding foam between the framing and reveal at the head, jambs and sill.

4   The sill joint must be appropriately rain-screened by the aluminium frame extrusion or otherwise.

Diagram of Sill Trays

 sill tray / sllblock diagram on a bridged polystyrene building block

Installation                                                                           Top

The Technical Literature provides full details for the installation of the tray, including opening details. The following is a summary of the main points only.

·         The sill trimmer must be level. 

·         The sill tray is cut to length to suit the opening width.

·         End sections are fitted and cemented to the sill tray ends.

·         The end sections are fixed to the studs through the fixing holes provided, with either galvanised plasterboard clouts or screws (AS 3566 Class 3 screws) approximately 30 to 40 mm long. Screws are recommended to allow for adjustments.

·         The Drainage Tray is fixed to the sill trimmer through the upstand support section at the rear of the tray (a scribed line is provided). The fixings must not penetrate through the sloping part of the tray, as this will compromise the water shedding capability of The Drainage Tray.

·         A building paper or wrap is fixed across the outer face and inside of the opening studs for the full height of the opening. The ends of the paper or wrap must sit over The Drainage Tray end sections so that any occasional moisture penetrating the joinery jambs area will collect on the paper or wrap and run down to the sill tray.

·         •When the joinery is installed care must be taken to ensure the sloping portion of The Drainage Tray is not penetrated by the sill reveal fixings.

·         The gap formed between The Drainage Tray and the joinery bottom flange must not be sealed, so moisture will drain to the exterior of 15" from the horizontal.


Basis of BRANZ Approval Cert.No.424(2001)                                                         Top

The following is a summary of the technical investigations undertaken:


Cyclic and static pressure water leakage tests in accordance with AS/NZS 4284 were carried out by BRANZ on typical window installations.

Other Investigations

1  BRANZ has assessed the practicability of installation of The Drainage Tray in a completed installation.

2  An assessment was made of durability by BRANZ technical experts.


1  The manufacture of The Drainage Tray has not been examined by BRANZ, but details of the manufacturing processes and quality systems, and quality and composition of the materials used were obtained and found to be satisfactory.

2 The manufacturer of The Drainage Tray has been assessed and registered by Telarc Limited as meeting the requirements of AS/NZS ISO 9002, Registration Number 300.

3   Quality on site for installation is the responsibility of the builder/contractor and/or window installer.


·         AS 3566 - 1988 Screws - Self-drilling - for the building and construction industries.

·         AS/NZS 4284: 1995 Testing of building facades.

·         New Zealand Building Code Handbook and Approved Documents, Building Industry Authority, 1992.

·         NZS 3604: 1999 Timber framed buildings.

·         The Building Regulations 1992, up to, and including the December 2000 Amendment.

See also: Redway Developments Ltd



Drainage Tray


Handling and Storage

Design Information

Service Life


External Moisture

Diagram of Sill Trays


IBasis of BRANZ Approval



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