Building with thin joint masonry
Could this modern blockwork system suit your building project? Emily Smith takes a closer look at this construction method
Emily Smith takes a look at how this modern construction method could benefit your self build scheme
Choosing your construction method is one of the first key decisions anyone undertaking a major building project will need to make. Masonry is still the UK’S most popular choice, but going down this route doesn’t necessarily mean using traditional bricks, as modern technologies have brought products to the home building market that offer advanced efficiency. The thin joint system is one such solution – here are the main benefits of this construction route.
1 It’s familiar
Thin joint gets its name from the narrow layer of special adhesive used to glue the concrete building blocks together. While traditional mortar beds (the cement-based mix between bricks) are 10mm taking up around 7.5% of the wall, thin joint is just 2mm-3mm thick and closer to 1%, meaning you need less material to build up the wall. The adhesive is delivered in bags as a powder, ready to be mixed on site simply using water in a bucket with an electric stirrer. Not only is it simple to put together, but the 25kg bags are also easy to store on site until needed.
Fundamentally, this is a build system that we can all recognise as masonry. Bedding the blocks is done in a slightly different way, using a special applicator, but it’s easy for brickies to get to grips with and super-quick.
2 Energy efficient results
This construction method uses aircrete blocks, which have been around in the UK since the 1960s. They’re a precision-engineered, lightweight alternative to dense traditional units, featuring an aerated concrete profile. They’re easy to handle, cut and drill – just ordinary hand tools work fine – plus they have better insulation values. The thin layer of adhesive means a faster build time and less room for air leakage between blocks, so the partnership creates an energy-efficient structure that can achieve impressively low U-values (a measure of heat loss where lower numbers indicate better performance).
Thin joint systems also allow a good level of thermal mass (although not quite as good as dense blocks). This means the walls are able to absorb energy from sunlight
and dissipate warmth into the home in winter, as well as create a cooling buffer in the summer to prevent rooms from overheating. All of this means these systems will help to cut energy bills and reduce your long-term carbon footprint – key goals for many self builders.
3 Sustainability credentials
The powdered form of the thin joint adhesive tends to mean there’s less waste on site because the just-addwater solution has a lean profile that doesn’t need to be created in massive batches. These sustainability points are further enhanced by the long shelf life of aircrete and its makeup – UK manufacturers generally use 80% recycled materials to create the blocks. “Aircrete’s environmental credentials extend to its eventual recycling at the end of a building’s life,” says Cliff Fudge, technical director at H+H. “As well as being an inert material that will far outlast the usual 60 year design life expectancy of a building, aircrete is easily recyclable and can be crushed down with other masonry material and used in future applications.”
Aircrete blocks have good sustainability credentials, then, but not everyone’s keen on using cement-based units. Thin joint walls can also be built using clay versions, such as Wienerberger’s Porotherm units.
4 Quick build time
Premanufactured timber frame structures come with a lead time while you wait for the shell to be created in the factory (usually 8-12 weeks) but the brick and block route allows you to start on site straight away. Typically, using thin joint will reduce build time by a few weeks compared to traditional masonry, with the shell coming together in roughly the same time it takes for a timber frame home.
The lightweight makeup of aircrete blocks means they are available in large-format units – helping walls to gain height quicker. “The internal side of the cavity walls can be built independently of the outer brick wall, so homes become weathertight sooner. The interior trades can then make headway with fitting out the inside at the same time as the brick outer leaf is being finished,” says Cliff.
That thin layer of adhesive also dries quickly, reaching full strength in just 15-20 minutes, meaning walls can be built up much faster than with traditional mortar. “Speed of construction is one of the major benefits when building using thin joint,” adds Cliff. “Traditional mortar takes time to set, with only six block layers being built in a day, whereas this reaches full strength almost immediately, allowing a whole storey-height wall to be constructed in one day.”
5 Versatile & affordable method
This construction type can be used for cavity walls, solid walls, basements and internal partitions, as well as party walls. “Thin joint is suitable for single and multi-storey buildings, even basement levels in either cavity or solid wall construction,” says Cliff. “Aircrete is also capable of meeting Passivhaus requirements.” The method has no limitations in terms of what style of property can be achieved. “Aircrete provides great versatility due to the ability to finish the exterior of your home however you like – you can use brick, render, pebble dash, weatherboard or pretty much any type of cladding you like,” says Cliff.
In terms of costs, you can expect to pay around the same as you would for a traditional masonry structure. While the larger blocks might come in at a higher price, you’ll claw back some savings thanks to the quicker build time and therefore less labour needed on site.