Avoiding Mortar 

Mortar has been used in roofing for hundreds of years. Its principle use is as a means of fixing and weather tightness at junctions such as ridges and verges.
 
Whilst mortar certainly does the job, there are a number of disadvantages it is worth being aware of. First, mortar has a limited lifespan and requires regular maintenance because it will deteriorate in time through natural weathering. Secondly mortar is susceptible to cracking because of the natural movement within the building structure, particularly where the roof passes over solid masonry walls. Once this happens, the ridges, hips or verges can become dislodged by high winds, and will be susceptible to water ingress
 
 
 

 

 

 

Over the years, manufacturers have developed systems that do away with the need for mortar. These systems, commonly known as 'dry-fix' roofing systems, offer a number of advantages over cement mortar:

1. Remove the need for regular maintenance of the roof. Over time, mortar can succumb to frost damage and building movement. When this occurs, repairs can be quite costly as scaffold access is often required. By eliminating mortar from the roof you can virtually eliminate any such maintenance.

2. Allows the natural movement within a roof structure to take place without damaging the ridge and hip fixings.

3. Provide the means to 'mechanically' fix ridges and hip tiles, greatly reducing the risk of storm damage.

4. Provide discreet roof space ventilation at the ridge and hip which helps control harmful condensation in the roof space.

5. Allows the roofer to complete the work safe in the knowledge that rain will not cause mortar to stain the roof or frost to damage the mortar before it has had chance to properly set.

 

1. Ridge Systems

Dry Ridge systems come in a variety of designs but offer a similar level of performance. They are designed to secure the ridge tiles which are located at the apex of a roof. When using dry ridge systems the mortar joints between ridge tiles are replaced by plastic inserts, known as unions, that create the visual appearance of a mortar joint but have a hidden weather proofing system that carries away the water.

The next significant component of a dry ridge system sits between the ridges and the tiles of the roof slope. This part of the system usually includes a ventilated strip that ensures moisture laden air is vented from under the tiles. The interface with the ridges and the tiles can be handled in two ways. The first method uses plastic inserts following the shape of the tiles, the second uses an adhesive roll which is corrugated and stuck down to the tile surface. Whilst the 'roll' systems are the most affordable, the profile system looks the best and offers an edge when it comes to longevity.

 Dry-Ridge.jpg

 A dry fix system replaces the mortar traditionally used at the ridge.
 

2. Hip Systems

A hip is the external junction between two sloping roof faces. As with ridges the traditional method of weather proofing this type of junction is usually to use ridge tiles which are then secured on a bed on mortar. 
 
Dry Hip systems eliminate the need for mortar and provide a more secure and maintenance free hip detail. The systems follow a similar design to dry ridge systems. The one key difference is when curved or profiled tiles are used, the dry hip system will rely on some form of tray to provide support along the length of the hip line. This tray helps ensure the roofer creates a neat hip line, without it the ridges would be sitting on the undulating tiles below. This would create an uneven hip line which not only looks unsightly but could affect the performance of the dry hip system (for example, it could leak).
 
Some products like plain tiles and slates do not require a dry hip system as they can be cut, or mitred, to the hip line with weatherproofing supplied by plastic or lead soakers that are laid underneath.
 
 
 Dry-Hip.jpg
 The dry hip system shown above replaces the mortar traditionally used at the hip.
 

3. Dry Verge Systems

A verge refers to the junction between the roof and the gable end of the building. A gable refers to the wall that infills between two opposite roof slopes and usually finishes in a triangular shape. The traditional way of finishing the roof at a gable wall is to use mortar. Traditionally this detail includes a layer of plain tiles, slates or fibre cement board to assist in the weatherproofing. Unfortunately all too often this type of verge is poorly installed, leading to eventual water ingress.  Even if properly installed a verge detail will require regular maintenance as it is prone to mortar failure.
 
Dry verge systems help avoid these defects and the need for periodic maintenance of the mortar bedding. For many tiles, special 'cloaked verge' tiles are available which neatly close the gap at the verge. Alternatively plastic dry verge systems are available which suit most tiles. These are available in single units, ie one piece per tile course, or in continuous lengths. These are attractive and highly functional ways to improving the overall appearance of your roof. The systems are easy-to-use and provide a neat, secure and mortar-less finish at roof verges.
  
A dry verge system will also reduce the risk of wind damage, water penetration and will stop small animals getting into the roof space.
 
 
The dry verge system shown above replaces the mortar traditionally used at the verge.
 
 

Do Dry Systems cost more than mortar?

This is not any easy question to answer as there are many systems on the market, plus a large proportion of the cost of both mortar bedding and dry systems is in the labour.  As a general rule the cost of the dry system per linear metre of ridge or hip will be slightly more than the cost of mortar. However, this additional cost of materials should be counter-acted by the labour saving benefit of using a mechanical system. Some contractors don't properly consider the true labour cost of mixing the mortar, getting it up to the roof and the time spend bedding and pointing each ridge or hip tile. Also, they may forget that if a ridge is mortared, other means must be found to ventilate, which means additional cost in tile or ridge ventilators.
 
On this basis using a dry system is usually cost neutral, that is until you take into account the future cost of maintenance. 
 

 

 
 
Jargon Buster

Not sure what each term means?

Click here for some basic roofing terminology.

 
 
Maintenance Plan

Missing tile? Cracked Mortar?

Download our Maintenance Plan here.
 
 
 
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