What Are Cavity Trays? What Are Cavity Trays Used For?
What Are Cavity Trays?
A cavity tray is a damp-proof course (DPC) that crosses the cavity of a cavity wall in order to prevent dampness from permeating the internal skin of a wall.
It is typically made up of a number of trays and is used to prevent rainwater from penetrating any cavity wall and causing water damage to windows and doors.
Cavity trays are lightweight, simple to install, and long-lasting solutions to the prevention of damp from entering walls.
Cavity trays can be used in a variety of applications, such as when the external wall changes to that of an internal partition below the roof line, or when inserted into existing walls for extensions.
They are also used as refurbishment systems, whereby they are folded to facilitate the insertion of a new tray into an existing wall.
Different types of cavity trays exist, such as self-weeping trays and catchment trays, and standards for their use have been established by organizations such as British Standards Institute (BSI).
What Are Cavity Trays Used For?
Cavity trays serve a range of purposes in construction projects. One of their main uses is to provide protection against water infiltration in areas where the external wall meets an internal partition beneath the roof line, such as gable abutments in new builds or lean-to extensions in refurbishment projects.
Cavity trays are also useful when a flat roof is resurfaced or rebuilt with added insulation, which can raise the level of the roof and leave gaps that allow water and damp to enter.
The simplicity and versatility of cavity trays make them a popular choice for builders and architects. The single-element system is easy to calculate and transport, and cavity trays are compatible with all types of building materials.
The bridging piece can accommodate cavity widths of 50mm to 100mm, providing flexibility in design and installation. Overall, cavity trays are an effective solution for preventing water damage and maintaining the integrity of buildings.
Cavity Tray Installation
The installation of cavity trays is an important feature in external cavity walls to ensure that any water is directed outside the building. Cavity trays should be installed directly above the opening/lintel and be in a single continuous length (without joints) wherever possible.
If joints cannot be avoided along their length, these should be rigidly supported and have a lap of at least 100mm, sealed according to material/product manufacturer’s details.
Cavity trays should also be installed over all external door and window openings including bay windows and at roof abutments, both horizontal and pitched.
British Standard codes of practice (BS 8215 and 8000-3) provide guidance on appropriate materials and installation methods to reduce the risk of defects in the wall structure.
The website cavitytrays.com provides fitting guides for installing cavity trays as well as information about Cavity Tray Standards.
What Is A Cavity Tray Made From?
A cavity tray is a flexible, pre-formed material such as lead or metal that can be molded into a range of shapes for different cavity widths, corners, stop ends, steps, lintel shapes, arch shapes and sometimes incorporating external flashing.
It is designed to protect the roof structure and walls from water penetration caused by rising damp or wind-driven rain.
Cavity trays are essential in preventing water damage to buildings and play an important role in increasing the longevity of a property.