CAVITY TRAYS LTD
LUFTON TRADING ESTATE
SOMERSET BA22 8HU
Tel: 01935 474769
Fax: 01935 428223
Suppliers of: cavity wall trays abutment cavity wall trays preformed damp courses cavity wall closers abutment cavity wall closers air bricks roof ventilation soffit ventilation fascia ventilation roof
Cavity Trays Ltd -Manufacturers of Cavity trays, DPCs, Radon Protection, Roof ventilation products & Cavity closers.
The only cavity tray manufacturer awarded European Technical Approval (ETA).
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Main Product Ranges:
A wide selection of Cavity Trays, profiled DPCs and ancilliary products for all construction methods. Cavity trays can be supplied in all sizes and shapes from load bearing lintels to masonry support systems. Damp proofing Courses (DPCs) are available in preformed & profiled systems to provide excellent Damp Proofing Solutions. Other products include weep vents, flashings, remedial products and arresting barriers for all damp proofing problems.
Cavity trays can also supply an extensive range of Membranes for all applications. These include: * Contaminated Land Gas Reception Sump * Gas and Water Outlets and Service Entry Points * Methane Barriers * Radon (Cavity) Barriers * Service Pipe Entry Seals (top hats) * Type N Sitesealer Membrane
Cavity Trays supply a wide range of products to solve ventilation problems on all contruction projects. Products include: Air bricks, sleeves, Ventilators, Roof vents, roofline Ventilation for Soffits, eaves and Fascias.
Cavity Trays offer a wide range of associated products to include: Masonry Attachment Profiles, Loft access doors & hatches, Eaves Protection, Bonding strips and valley gutters.
Cavity Trays supply a wide range of Cavity Closers for all construction & refurbishment methods. Products include: Bespoke Traditional Cavity Closers, Fire integrity stops & barriers, Acoustic barriers, waterproof barriers, insulated cavity closers & barriers.
Main Product categories:
Threshold cavity trays, Cavity cloaks, DPC, Remedial cavity trays, Cavity trays, Party wall trays, Cavity weeps, Wall ventilators, Valley gutters, Cavity closers, cavity closers sash frame, Fire barriers, Fire stops, Cavity closers wide cavity, Access panels fire resistant, Access panels, Cavity socks, Damp proofing membranes, Dampcourse jointing tapes, Dampcourses gas resistant, Membranes Contaminated land, Radon protection systems, Roof space ventilators, Ventilation grilles, air bricks, air brick adaptors, Ventilation roof void, Ventilation roof space.
Cavity Wall Reveal - Improved Performance
Cavity Wall Reveal - Improved Performance The review of Part L highlights the importance of addressing unnecessary heat-loss from a building. Possibly one of the most commonplace areas of thermal bridging is around window and door openings. These literally punctuate the cavity wall at all levels and so doing creates opportunities for thermal bridging at the reveals.
Often overlooked is the extent by which an exterior skin material will worsen the heat loss path (and so challenge the intended thermal wellbeing around an opening) whenever the masonry skin becomes saturated with water.The conductivity of a brick does not improve when wet, quite the contrary. But how often is this taken into account when considering the overall performance of the structure? Can a reveal detail that marginally complies with Part L requirements remain compliancy when the structure is wet?
The thermal conductivity of any material depends on temperature, density and importantly its moisture content. When a material becomes wet, the air enclosures fill with water and the conductivity of the material increases because water is a better conductor than air. A dry brick might have a specific mass of 1600-1900 kg/m³ and thermal conductivity of 0.6-0.7 W/mK.
The same brick when wet can have a thermal conductivity of 0.9 – 1.2 W/mK. An increase in conductivity approaching 100%.
This should be borne in mind when calculating any heat loss path given the proximity of a wet outside skin with the reveal closing arrangement. Here is a prompt list of possible improvement aspects designers and builders might consider:
1) Use a Cavicloser that permits variable frame positions rather than just a fixed one. Moving the frame further back within the reveal within the permitted parameters can shorten the heat-loss path through the exterior skin and lengthen the path through the interior skin. Check whether this might benefit your openings.
2) Instead of using an ordinary cavity closer consider using a Continuity Closer. Continuity Closers link with the cavity insulation and so block the commonplace gaps that occur and provide heat-loss paths. A Continuity Closer can cost no more yet can raise the performance compared with a non-interfacing alternative. (Gaps contravene Approved Document L1A 5.9 that states the building fabric should be constructed so that there are no reasonably avoidable thermal bridges in the insulation layers caused by gaps and refers to those at the edges of elements such as around windows and doors).
3) Ensure any penetrating water arrested by a cavity tray, lintel or DPC is quickly evacuated from the structure and not retained within it. The more quickly the masonry dries out the more quickly the thermal performance improves. Caviweeps provide water exit routes – select from the various models available. Some are dual-function and can function despite directly-blowing wind pressure.
4) Opening heads and opening sills can receive insulation infill’s that reduce heat loss. Compressible Cavistops are ready-shaped to suit the area into which they are fitted and provide acoustic and thermal qualities. They take just seconds to install and friction-fit. Always review the calculated performance of any opening through a cavity wall. How it changes when gaps occur between cavity insulation and reveal closer. The thermal deterioration when the exterior skin masonry becomes saturated.
Cavity Trays tech manual provides best practice advice for terraces and balconies
Cavity Trays’ technical manual provides best practice advice for terraces and balconies
Specifiers should always consider to what extent water might penetrate a balcony or terrace outer cavity wall, and where that penetrating water might end up.
In the example shown, the exposed outer parapet wall to the high level terrace incorporates an inward-stepping DPC with a flashing under to dress over the terrace surface upstand. Whilst acceptable in theory, the arrangement is flawed. When the exposed outer skin saturates, water can track on the underside of the inward stepping DPC, feeding wet directly into the room(s) below.
In situations where there is living accommodation below the terrace, it is essential that the protective DPC arrangement steps outwardly – despite it being shown otherwise in some technical manuals.
A similar scenario exists with doorways providing access onto an upper-level terrace with rooms below. The protective arrangement in the cavity wall must step outwardly. It should also be remembered that the Building Regulation requirement of ‘fins’ on reveal cavity closers guides penetrating water downwardly, so any adjacent DPC horizontal arrestment detail must interface to receive and evacuate water at that level. Failure to do so can allow water to continue downwardly, discharging from closer fins into the area under - that is supposed to be kept dry.
Masonry skins of all thicknesses can saturate, including exterior skins of 225mm (two-brick ) thickness. Beware of potential under-tracking with any inward stepping DPC in a cavity wall.
The 200-page Cavity Trays Best Practice Technical Manual demonstrates how such weakness can be eliminated using preformed outward-stepping approved Cavitrays and compatible interfacings.
Cavity Trays of Yeovil is the longest-established UK company in its specialised field and the only UK tray manufacturer awarded European Technical Approval.
T: 01935 474769