It is an internal moisture or water barrier made up of a number of trays. The purpose of it is to prevent rainwater from penetrating any cavity wall and causing water damage to any windows and doors within a conservatory or orangery design. Damp typically occurs as a result of rainwater soaking external brickwork and forcing its way into the cavity between the inner and outer walls. Serious consideration should be given to a cavity tray when the external wall of the house is modified into a rear internal wall to accommodate a new conservatory, orangery or solid roof installation.
Most modern bricks are susceptible to absorbing water which is why a lot of newly built properties have small plastic vents positioned above ground level windows and doors. They’re better known as ‘weepers’ and are designed to let rainfall flow out of them when they connect with the lintel supporting the brickwork above the windows and doors. Despite these ‘weepers’, some of these buildings still require a cavity tray.
The compass orientation and height elevation of the relevant side of the house will also determine if a cavity tray is likely needed as properties facing south or south west are more exposed to rainfall. The amount of brickwork used above any ground floor windows and doors will similarly play a part in the decision.
You should also remember that we live in a perennially rainy country and if the scientists are right, Britain will become even rainier in the future. This incessant rain has seen the retrospective fitting of cavity trays to many existing extensions that previously didn’t have one.
So, it may make sense to include one in your plans when everything is being costed up as you will be charged extra for the integration of a cavity tray. We will be upfront and honest as to whether we feel you need one and will only be able to determine this once we have analysed the building to see if there is a chance of excess rain causing ‘wet wall’ problems or damp.
Our hottest early May bank holiday ever was a very welcome surprise and hopefully a sign of things to come as we inch every closer…
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