This page forms part of our blog which contains a series of hints, tips and advice for consumers and tradespeople.
Whether you’re working in the trade or are a homeowner looking to make sense of the odd terms used in the construction industry, this guide is for you.
What is a wet roof fixing method?
Any fixing system that claims to be “wet” is one that uses concrete mortar as the primary method to secure the roof tiles in place.
The photo below shows ridge tiles being bedded onto mortar:
Why Wet Systems Fail
While most people think that concrete mortar is a strong material that’ll last forever, the truth is often very different.
When a roof on a typical house is constructed, the weight of the tiles presses down onto the roof timbers and causes some flexing and movement.
Most new houses will experience between 5-30mm of movement in the roof. This usually occurs within the first few years after construction.
While this is quite normal, it does have an effect on the mortar which is holding the tiles in place.
Mortar doesn’t like movement, it often cracks and can crumble.
Also, wet concrete mortar can’t be used when it’s raining or when freezing weather is forecast.
The end result is often something similar to this:
Failed mortar and loose ridge tiles
Failed mortar can crack, fail and the tile can come loose.
Needless to say, a loose tile like this could be blown off the roof on a windy day and potentially kill someone.
Changes to British Standards (BS 5534)
In 2010 the NHBC (National House Builders Council) saw a 60% increase in the number of claims relating to pitched tiled roofs.
Most of the claims were a result of mortar failure.
This, along with an increase in adverse weather, led to several changes in the requirements of British Standards.
These changes are now in force.
BS5534 states that mortar can no longer be used as the sole means of securing roof tiles in place.
To meet the new requirements, a mechanical fix such as a screw or clip should be used either with mortar or to replace it.
The Dry System
The dry fix system secures the roof tiles to the roof without any mortar whatsoever.
Take a look at the photo below:
As you can see, a clip secures the tile into place and allows for plenty of movement, there’s no mortar to crack and the tile can shift and move with the roof without breaking loose.
This type of fixing system is now used on almost all new build roofs.
It’s also becoming more popular on refurbishment projects.
The Hybrid Fixing System
The hybrid fixing system is one that uses mortar for aesthetic purposes whilst adding a clip system to guarantee that the tiles won’t come loose.
Below is a photo of a wet system and a dry system combined, i.e a hybrid:
The Pros and Cons of Each
Below you can see the pros and cons of the wet fix, dry fix and hybrid systems:
The Wet Fix System
Pros
- looks traditional
- will blend in neatly with neighbouring roofs if you’re using it on a refurbishment project
Cons
- can crack and tiles may come loose (more likely on new homes because the roof takes a few years to settle)
- time-consuming
- mortar will fail if the temperature drops below freezing before the material has set
- cannot be laid in the rain
The Dry Fix System
Pros
- quick and easy to lay
- can lay in rain and cold weather
- it’s quick to learn this installation method
- secure tiles with little chance of them coming loose
Cons
- not as aesthetically pleasing as mortar
- may look out of place on a traditional property
- potential issues with listed buildings
The Hybrid System
Pros
- secures the tiles
- keeps the roof looking aesthetically pleasing
Cons
- takes the most amount of time to complete
- mortar cannot be laid on wet or cold weather
My preference is the hybrid fixing method as it securely holds the tiles in place but looks better.
What About Building Regulations and “The Law”
The British Standard (BS 5534) does not form part of the building regulations and is not enforceable by “the law”.
British Standards only apply to roofers that have agreed to abide by the requirements.
A good example of this is house builders that offer a 10-year NHBC guarantee. The NHBC require all roof tiles to be fixed in accordance with British Standards.
While this agreement is not “the law”, it does form a contract that could be enforced through a civil court.
If you comply with a British Standard then it’s pretty clear that you take your responsibilities seriously as an organisation, and indeed compliance is often taken as evidence of due diligence. It certainly speaks volumes about your attitudes to doing things properly. However, standards aren’t the same as regulations and following a standard doesn’t guarantee that you’re within the relevant laws. – BSI Group
What About Refurbishments?
Many roofing firms are now using either the dry or hybrid fixing system for refurbishment projects as well as newly built homes.
While most people feel that the British Standards are “best practices”, there are some reasons why a roofing firm may consider a wet system instead:
- the property is listed/graded
- for purely aesthetic reasons
- the property is in a very sheltered location
- the roofer feels that the roof has settled and is unlikely to experience any further movement and a wet system will suffice
Our Recommendation
We recommend that all roofers use either the dry or hybrid system unless there are valid reasons not to, such as the property being listed.
Other Types of Tile That Can be Dry Fixed
The photos further up on this page show ridge tiles and the various fixing methods.
Similar fixing methods also apply to verge, hip and other tiles.
See the photos below:
Plastic dry verge system
Hip system with clips for cut tiles
Get a Quote
If you need a quote for roofing work, just hit the link below and fill out the form.
It only takes 2 minutes to get the ball rolling:
