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Leaded for Blockwork Cavity Trays

BBA approved stepped cavity tray system supplied with integral lead flashings for installation at the abutment of pitched roofs of 12.5°+ with an external cavity wall.

For external walls not exceeding 150mm thickness and built from block or stonework with regular course heights, including mortar, of approximately 225mm and clear cavity widths of between 50mm and 125mm

  • trays to suit clear cavity widths of 126mm + are available to order.

Supplied with factory fitted lead flashing (long or short), which presents a quicker and straightforward installation as the cavity trays and flashings are installed in a single operation, rather than multiple trades, as well as a consistent protective and aesthetical finish.

Choice of 2 cavity tray lengths to suit specific roof pitches with a variety of base widths for different wall thicknesses and clear cavity width combinations.

Also available unleaded (for lead flashing to be supplied and fitted separately site fitting) or supplied unleaded with convenient mortar barrier strips (to aid the installation of post fitted lead flashings).

In comparison to alternative on-site DPC fabricated methods; preformed cavity trays present many features and benefits including reliability, speed of installation, reduced cold bridging opportunity and site waste.

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Features & Benefits

  • Robust and reliable DPC method
  • Saves time, labour and material wastage
  • Consistent aesthetic and protective finish
  • Permanent stopend protects the perp joint and cuts out water backtracking along the blockwork
  • Reduces cold bridging opportunities
  • 150mm high back self-supporting upstand
  • Built into the outer wall leaf only allowing both internal and external leafs to be built independently
  • Quicker and simpler to install compared to alternative DPC methods
  • Won’t degrade over time and doesn’t change or distort under high loads
  • Isn’t affected by high or low temperatures
  • Won’t drop and collapse into the cavity
  • Doesn’t usually require cutting into insulation
  • Can be prepared in convenient plot specific order consignments

Applications

Preformed stepped cavity trays ‘step up’ the external cavity wall in order to follow the abutment of a pitched/gabled roof such as:

  • attached garages
  • conservatories and extensions
  • porches and bay windows
  • attached buildings with different roof lines.

Choice of 2 cavity tray lengths:

  • 625mm for roof pitches of 25°+
  • 1250mm for roof pitches of 12.5-22.5°

For external cavity walls built from blockwork or stone:

  • with regular course heights of 225mm inc. mortar
  • not exceeding 150mm thickness
  • with clear cavity widths of between 50-125mm
  • made to measure design and manufacturing service available for non-standard projects.

Technical Information

With pre-formed cavity trays it’s not strictly necessary for the tray to span all the way across the cavity (except projects in severe weather exposure areas).

As long as the cavity tray stands back from the rear face of the masonry and projects back into the cavity far enough to intercept drips falling from the wall ties, then it will perform effectively.

If installing cavity trays with a partial fill cavity insulation, please deduct the insulation material depth to calculate the available ‘clear cavity width’.

The different types cavity trays in a stepped system:

  • intermediate cavity tray – suits all cavity options and forms the main tray run with one tray on each course of brickwork running the full length of the abutting roof slope
  • stopend starter cavity tray – this is the first component to be installed and fitted at the lowest point on a standard abutment. It collects the water that is gathered by the rest of the system and discharges it from the wall through a weep hole or vent
  • corner starter cavity tray –this has the same function as a stopend starter tray, but it is used where the abutting roof comes up to, or beyond, the corner of the main building. It is designed to return around the corner of the building to provide complete protection from water ingress
  • ridge cavity tray – used where a right and left hand roof slope come together at an apex to straddle the top two intermediate trays
  • weep holes and vents - cavity trays must be installed in conjunction with proprietary weep holes or vents to ensure that any water collected with the cavity tray system is discharged back out through the external wall leaf.

We strongly recommend the specification and installation of purpose made wall weep/weep vent products, such as Timloc’s 1143 wall weep vent or TW1 concealed wall weep ranges to guarantee an accurate fit with the tray and a reliable discharge of water.

Calculating Quantities of Stepped Cavity Trays

We strongly recommend that customers take advantage of our free cavity tray specification and project scheduling/take off service.

Our Technical Services Team will be pleased to advise on the most suitable products to suit your project and will prepare a fully itemised schedule of quantities if required.

To calculate quantities allow one cavity per course - on each roof slope including:

  • one stopend starter or corner starter tray per roof slope (bottom)
  • one ridge tray at each apex (top)
  • one intermediate cavity tray per brick course (between the ridge and stopend/corner starter cavity trays).

Check the roof pitch and select the correct length of tray to suit it.

Select the correct handing to suit the direction of each roof slope.

With all stepped cavity tray enquiries please state the:

  •     type of roof construction (pitched, mono, flat)
  •     roof pitch
  •     length of abutting roof
  •     external wall material and thickness
  •     clear cavity width
  •     cavity insulation material and thickness
  •     are leaded, unleaded or unleaded with mortar barrier strip trays required?
  •     are long or short lead lengths required?

Alternatively, please send the project drawings through to us and we can take it from there for you.

Lead Flashing Lengths

All leaded cavity trays are available with a choice of long or short lead lengths.  It is important to specify which is preferred.

Generally:

  • standard short lead lengths are used for dressing over upstands of secret gutters and seperate soakers
  • standard long lead lengths are used for dressing over profiled tiles
  • we can prepare lead flashings in any lead length to suit any roof pitch - please contact us with your project details.

Installation Advice

On-site installation and best practice guidance is all part of our service, please don’t hesitate to contact us to arrange a site visit.

When specifying or installing stepped cavity trays it is important to consider the following recommendations:

  • With preformed cavity trays is it not always necessary for the cavity tray to span all the way across the cavity.
  • As long as the cavity tray stands back from the rear face of the stone and projects back into the cavity far enough to intercept drips falling from the all ties, then it will perform effectively.
  • Ensure that the run of cavity trays protects the abutment fully from eaves to ridge.
  • The first (lowest) tray should project just beyond the eaves line of the roof.
  • Further cavity trays must be installed on every course for the full length of the abutting roof slope.
  • Trays should be positioned on a line parallel to and 75mm above the top of the finished roof line.
  • It is essential that some sort of guide line is set to work to.
  • Allowance must be made for the thickness of the roof timbers, tiles, battens, etc. so that the line represents the top of the finished roof line.
  • Cavity trays must always be bedded onto fresh mortar, never dry bedded.
  • The blockwork laid over the cavity trays must also be bedded onto fresh mortar -approximately half way through the mortar joint.
  • The cavity area must be kept clean and free from mortar droppings and debris.
  • The first cavity tray installed at the lowest point on the abutment must always be a starter tray of some description.
  • The main body of the cavity tray run is made up of a series of intermediate trays, with one positioned on every course for the full length of the abutment.
  • Intermediate trays are either left or right handed - ensure that the correct hand is used to suit the direction of the roof slope (the closed end must be positioned closest to the roof line and with the open end positioned away from the roof).
  • The corner of the closed end of the tray should be positioned on the guide line, 75mm above the finished roof line.
  • Each cavity tray should overlap with the next.
  • Weep holes must be provided in the face of the wall.
  • In exposed locations or if porous masonry is being used, then additional weep holes must be provided.
  • We strongly recommend purpose made weep holes such as Timloc’s 1143 and TW1 ranges.
  • High quality workmanship, cleanliness and attention to detail are essential with all cavity tray installations.

Please don’t hesitate to contact the Timloc Technical if there is any doubt regarding the correct method of installing cavity trays.

Quality, Standards and Regulations

  • BBA Approved
  • Satisfies all NHBC requirements
  • Manufactured to BS EN ISO 9001 quality management system
  • Manufactured to BS EN ISO 14001 environmental management system
  • Complies with all relevant Building Regulations
  • Meets all relevant British Standards
  • Flashings are Code Blue (Code 4) milled lead as standard as defined by BS EN 12588:1999

Materials and Colour Choice

  • Flashings are Code Blue milled lead as standard (formally known as Code 4)
  • Heavier codes of lead are available for:
  •   - areas of severe weather exposure
  •   - flashings to be fixed and sealed where they overlap
  • Injection moulded 2mm polypropylene cavity trays for durability
  • Cavity trays are available in black only


 

  • nbs plus
  • riba

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