The vast majority of buildings constructed nowadays incorporate cavity walls in their structure, and have done largely since the 1920s. This means that the exterior has what is known as an outer leaf layer (which is commonly composed of brickwork but sometimes other such blockwork or stone) and then an inner leaf layer (which is usually made up of those big grey blocks which are bigger than bricks and are often referred to as ‘breeze blocks’ – chances are you have probably seen them at some point). Between these two layers of masonry is a gap – hence the expression ‘cavity wall’. They are very susceptible to dampness.

Outer leaf brickwork is porous

The bricks which are used for the outer leaf brickwork of most buildings are a lot more porous than you might think, despite their sturdiness and strength. Indeed – such bricks have tiny interstices in them and this basically means that liquid and air is actually quite easily able to pass through. Strong, wind-driven rain often penetrates and saturates outer leaf brickwork and this moisture finds its way into the building’s wall cavity.


How this can cause damage to your conservatory

Dampness and moisture in the cavity wall is therefore rather common and not really a problem whatsoever – unless the wall in question has a roof adjoining it, as is the case with conservatory and extension roofs. This can be a major problem.

When a conservatory is added to a home, it changes the function of the outside wall – which is now technically inside the house – into, well, an inside wall of the conservatory. So, when rainwater gets in the outer leaf brickwork above the conservatory or extension roofline and then trickles down – as of course it will do naturally – the rain-soaked brickwork of the original outside wall (which, bear in mind, is now an inside wall to all intents and purposes) creates a damp interior wall. To say that this is something you should try to avoid is putting it extremely lightly, as it can cause quite serious problems and lasting damage to your internal rooms and the inside of your house.

If you live anywhere in the British Isles, the chances are your area experience its fair share of rainfall each year, especially in the winter. Of course, some areas are more subject to rainfall than others, but all the same it just takes one particularly aggressive downpour and you will be at the mercy of cavity wall saturation. Therefore, you will need something to combat it if and when it happens.

Why your conservatory needs to have cavity trays installed

Thankfully there is a solution, and it is cavity trays. How do they work?

The concept of the cavity tray is really quite simple, but at the same time it is actually somewhat ingenious. They are plastic sloping trays which are put in place in the cavity between the outer leaf brickwork and the inner leaf blockwork, just above the roofline of the conservatory or extension roof.

So, when rain finds its way in through the outer leaf brickwork, it cannot trickle down below the roofline to dampen the inside wall, because the cavity tray is there to intercept it. The rainwater is then deflected back out through the outer leaf brickwork and onto the conservatory or extension roof, because that is where the cavity tray is positioned just above the roofline.

The water consequently runs down and off of the roof then into the gutter and down the downpipes – as it should. If this happens, everything has run smoothly. This will not happen without the implementation of cavity trays. This is what needs to happen in order to prevent the brickwork inside the conservatory getting damp and becoming further problematic thereby.

Building regulations now dictating that dampness-prevention measures must be taken during construction

Building regulations in many countries now – quite rightly and wisely – dictate that the most thorough of measures must be taken to ensure that new buildings are safe in regards to moisture, both for the building’s sake and the people in it.

In Scotland, their 2013 Building Standards states:

“Every building must be designed and constructed in such a way that there will not be a threat to the building or the health of the occupants as a result of moisture from precipitation penetrating to the inner face of the building.”

Be very careful who you hire to construct your conservatory or extension

Cavity trays are exactly the sort of dampness-prevention measure that building regulations are starting to make compulsory. If your conservatory or extension is constructed without one in this day and age, well then, quite frankly, you have made a huge misjudgement regarding who you have hired to install it. No reputable or conscientious tradesperson or outfit would even dream of not putting in cavity trays – it is quite simply a corner you cannot get away with cutting.


There are different types of cavity trays

There are a few different types and shapes of cavity trays, and the ones used for diverting water onto conservatory roofs are generally referred to as ‘horizontal’ cavity trays. As you may have guessed, this is because they deflect the water horizontally. These are the ones you will need, most likely.

If cavity trays are being installed into an already-existing conservatory that was, for whatever reason, not fitted with them when it was built, the general method of installation is that two, three or four bricks (depending on the length of the horizontal cavity tray) on one row are removed at a time, and the trays are then slid in and positioned so that they can perform their function.

Conservatories deviating from their original definition – now much more permanent

The dictionary definition for the word ‘conservatory’ states that it is essentially a mostly glazed structure – a greenhouse even – used to house plants, in which people occasionally sun-lounge if they so desire. Now, though that is indeed the traditional function of conservatories, we now think of them as much more solid and permanent brick-laden structures – because they are.

For this reason, the construction of your conservatory is something that needs to be taken very seriously. It is always best to hire somebody or a firm that you know are good, come highly recommended or are renowned in your local area. Do not choose who builds your conservatory based solely on how much they charge. Paying a bit more for someone who will do a thorough and skilled job is always the wiser option: cutting corners financially on the construction can end up costing you an arm and a leg in repairs or modifications later on. Remember – it is not only the new conservatory (or extension) part of the house that can be damaged if it is poorly constructed, but the rest of the house as well.

Many older conservatories will not have cavity trays

It is mainly older conservatories that do not have cavity trays in place. Though they have in actual fact been around for years, it could be said that it is only over the last few that they have started to be taken as seriously as they should be. They are becoming a legal requirement at long last.

When looking at houses as a buyer, keep your eyes peeled regarding the little yet important things like cavity trays

If you are ever looking at a house that already has a conservatory installed, make sure you find out whether it has cavity trays or not. Though you could quite easily have some installed if not, a great deal of damage to the inside walls may already have been done and could end up costing you some serious cash.

Other things you can do to improve an already existent conservatory

  • Add some nice furniture

You want to be your conservatory to be somewhere you are comfortable in. Don’t just furnish it with any old neglected chairs or sofas, as you won’t want to spend any time in there. The idea of a conservatory is to create another room of relaxation which is especially pleasant in the summer.

  • Make sure it is as energy efficient as possible

Especially if it is connected to your living room, it is imperative that as little heat as possible is lost during the colder months. Get parts of your conservatory refitted if you think it might be losing heat – a wise and necessary investment for sure.

  • Ensure the doors are of good quality

This will help with both energy efficiency and security. A lot of heat can escape through the doorway because it covers such a large surface area – and don’t forget, there will most likely be the doors connecting your living room (or kitchen) to the conservatory, and another set connecting the conservatory to the garden or patio, too.

  • Put in some plants

After all, this is the original idea of the conservatory – to house and grow plants. A great benefit to you, the conservatory-dweller, though, is that plants positively affect your overall happiness and well-being and reduce your anxiety and stress. On top of that, being around plants helps you concentrate, so if you have some work or studying to be getting on with, get in a plant-laden conservatory!

  • Keep it clean

Conservatories aren’t super-high maintenance at all, but they soon get a bit dirty inside and out. Just keep on top of it as you would all the other rooms in the house. All it takes is a cleaning of the floor and wiping the windows every now and again.


Things you will want to bear in mind when considering having a conservatory installed

  • Make sure you are completely happy with the design you have chosen

Pick one that looks and relevant now but also one you think you will still like in a few years – conservatories are much more fixed and permanent now than they used to be. A lot of time and money goes into them – your money, that is.

  • Make sure it is designed to be secure

You want a conservatory that will give you a great new relaxation area that brings you closer to the feeling of being the garden, but you need to make sure that it does not in turn provide unwelcome intruders with an easy break-in point. Every modern conservatory needs to have sturdy windows and doors – not just a lock on the door.

  • Ensure it is as energy efficient as possible

If you invest in a conservatory of substandard design and construction, you could end up wasting a lot of money on energy you are not getting the benefit of. A poor quality conservatory can hemorrhage heat – just like if you left the front or back door open, and you wouldn’t do that!

  • Make sure the roofline has good guttering fitted

You need to have highly effective guttering and downpipes installed, just as on the rest of the house, in order to ensure that rainwater does not settle where it shouldn’t. This can also make a massive difference to your conservatory looking smart and well-finished and it looking like a scruffy and neglected part of the house, so make sure it matches the rest of the house’s guttering and is of the highest quality possible.


At the end of the day, the conservatory is a part of your house like any other, and it is crucial that everything is properly done as to both save you headaches and not devalue the house at all. Getting cavity trays installed is a relatively simple process – the professionals know how to do it and also how to rectify any damage that has already occurred as a result of there being an absence of cavity trays, so call a reputable company and ask for a price quote. It is a small investment that goes a very long way!