What is a dry ridge system?
Dry ridge refers to a method of mechanically fixing ridge tiles or hip ridge tiles to a roof without the use of traditional sand and cement mortar.
Dry ridge, rather than relying on mortar for a bond, instead employs a dry fix system that typically uses screws – often stainless steel – to attach clamps between the joints of every ridge tile, clamping them to the roof. Beneath these screws are waterproof unions that catch any small amount of direct rainfall and disperse it sideways back onto the roof itself.
IS DRY RIDGE ANY GOOD ?
In a word yes. In fact they are now a building control requirement on all new roofs since BS 5534 was introduced, although repairs to existing roofs are exempt, as are some listed and period properties under the right conditions. The benefits of a dry ridge system are as follows.
- Will not blow off – There are many things that can affect the lifespan or bond of mortar bonded ridge tiles. Dry ridge however (as long as it has been installed correctly) will not blow off under normal conditions, greatly reducing the risk from storm damage. No more ridge tiles landing on the floor, car or conservatory after high winds.
- Maintenance – Unlike mortar there is nothing to maintain, mortar mixes will degrade over time, sometimes prematurely.
- Ventilation – Dry ridge provides discreet ventilation of the roof space and helps to stop any harmful buildup of condensation, as described on my roof ventilation page.
- Movement – Believe it or not roofs move. This can be through vibration (near main roads or train tracks) or through natural expansion and contraction. Dry ridge allows for all types of movement.
DIFFERENT TYPES OF DRY RIDGE SYSTEMS
Dry ridge comes in two main types, and although similar to each other they can have their own dedicated fixing systems. Luckily good dry fix ridge kits are now available that work for both ridges and hip ridges, this is called a universal dry ridge system.
WHAT IS DRY RIDGE
The ridge normally refers to the fixing of ridge tiles located at the top of a roof or the apex. This could be for instance where the roof, or a section of the roof, would go straight up and down, from front to back. This situation would require a standard dry ridge kit, or the universal system.
WHAT IS A DRY HIP RIDGE
There is a subtle difference between the dry ridge above and a dry hip ridge. Hip ridges cover an external junction between two sloping faces of a roof, and these are usually seen on roofs with 3 faces or more, and at least one of those faces is usually a triangular shape. Although roofs can have a combination of both ridges and hip ridges. This type of roof would require a dry hip ridge system or a universal system.
Often when fitting hip ridges you also install hip trays, or hip support trays. The function of these is not only to add additional waterproofing underneath the ridges, but to help create a neat visual line by providing gentle support to the underneath of the ridge tiles themselves. This is particularly useful in either exposed weather locations or on profiled roof tiles, when not using them can not only make to ridge line look undulating and uneven, but also compromise the waterproof unions.
CAN I CONVERT MY SLATE OR TILED ROOF TO A DRY RIDGE SYSTEM ?
The answer is almost certainly yes with a dry ridge conversion. When the existing mortar on your roof or ridge tiles ages it may become an ideal candidate for dry ridge conversion. This usually involves removing your existing ridge tiles and either reusing them or replacing them. A Dry ridge system can then be used instead of traditional sand and cement, and I can only think of two common obstacles.
- Firstly your existing mortar has to be in a loose enough condition that it can be removed from both the surface of the roof and any ridge tiles you wish to keep. If they aren’t loose it’s not worth potentially damaging the roof to achieve this goal.
- Secondly the ridge tiles if being reused may be problematic if they are handmade clay, or of an unusual design. In which case mechanical fixing and mortar may be a better option.
DRY RIDGE VS MORTAR (SAND AND CEMENT)
Dry ridge isn’t always suitable or desirable, especially on some period properties. The good news is there is an alternative to dry ridge, and as long as you are not having a ‘new roof’ you can still rebed or re-lay loose ridges with mortar in the traditional manner, and if done correctly it should last many decades.
The exception to this is that in certain locations wind can channel and blow off traditional mortar bedded ridge tiles time and time again, sometimes whilst avoiding all other properties in the process. Over the years I have known this phenomenon and in this case it’s best to admit defeat and convert to dry ridge, or a compromise as mentioned below.
Alternatively traditional mortar can be combined with mechanical fixings too and this can work on both a new roof or remedial work. Of course there may be other solutions too and these can be discussed with either your roofing contractor or architect.