The face of Irish construction is changing, with pressure on Architects, Specifiers, Contractors, Builders and Manufacturers mounting to provide more housing, better, faster, and cheaper. The challenges are not insignificant. The housing crisis certainly demands that we embrace rapid build solutions, but we cannot afford replicate the mistakes of the past, sacrificing quality and performance in a bid to populate the country with quick built houses.
We know the standard of new housing must exceed that of the past in more ways than one. We’re painfully aware of the importance of fire performance in our building. Add to this the looming nZEB standard (Near Zero Energy Buildings), which tasks us with finding solutions to improve the energy efficiency of our homes by a further 10% over current regulations, and a whopping 70% over those built just 10 years ago. Improved U-values, better airtightness, carefully designed junctions to reduce thermal bridging, oversized renewable energy systems, better ventilation, the list goes on.
The concern for many of course is that achieving all of these goals will see a significant increase in the build cost, a potential scenario that everyone wants to avoid.
Each demand on its own is achievable, but as we add one to another, and another, and another, it may begin to feel like an insurmountable challenge. How can we achieve it all, fast? It demands a fundamental change in how we build houses, one which will require the entire industry to embrace willingly, and quickly.
Learning from Europe
It’s at times like these that we need to learn from what works for other nations, and understand how their building practices can be effectively adopted here in Ireland to achieve the desired advances in our construction industry. And so, we turn to Europe. Nations such as Germany and France, and many more, who share a common method of construction as standard: single leaf thin joint masonry construction.
Single leaf thin joint masonry is not a new concept, although it is rarely adopted in Ireland. These European countries have been using it for years, and for good reason. The benefits of using single leaf thin joint masonry include quicker construction, enhanced thermal performance and improved airtightness versus traditional cavity wall construction.
When we look at how this build method stacks up to the increasingly popular timber frame house, the comparison shows thin joint is cheaper to build and offers up to six hours fire resistance versus the typical thirty minutes for timber framed construction.
Already, we can see how this construction method starts to tick the boxes on our wish list: faster, cheaper, better. Couple this with a host of other benefits, such as reduced waste on site, increased productivity, the fact that it uses skills already used in Irish construction, so there is no risk to the block layer willing to adopt this method, and the potential is huge. Time to start looking at this as a serious contender? Absolutely!
What is thin joint construction?
Thin joint construction is a modern method of construction which utilises a 2-3mm fast setting adhesive in place of the traditional 10mm general purpose mortar joint. It’s commonly used in conjunction with aircrete blocks (e.g. Quinn Lite) due to the exceptional dimensional accuracy achieved during the manufacture of this product. This coupled with the fact that aircrete blocks have a far superior thermal performance when compared to dense concrete or lightweight aggregate blocks, makes this a perfect solution for low energy builds.
Thin joint and rapid build
This is crucial to the successful adoption of thin joint construction in Ireland. Construction firms and builders are under pressure to deliver more housing, and they need to look at rapid build construction methods to meet the demand. This has resulted in a rise in timber frame construction, but this comes with its own limitations, particularly relating to fire performance. Timber frame construction can require hefty upfront deposits and result in lengthy delays whilst the frame is being fabricated, something which we don’t have to contend with when using thin joint masonry construction.
When compared to traditional cavity wall construction, single leaf thin joint masonry construction is approximately 60% quicker. This stems from the fact that there are only half the number of blocks to be built in the external walls. In addition, it has been proven that building with thin joint mortar is 20% faster than general purpose mortar.
With the structure going up so quickly, the roof can go on and the building can be made weather tight much sooner than with traditional masonry construction, allowing internal trades to commence long before the insulation and external finishes are applied.
From 1st January 2019 the new nZEB requirements will apply to all new public buildings, with all other buildings following thereafter. Basically, what nZEB means for dwelling is an A2 BER rating and an energy value of 45kWh/m2/annum or less. The Energy Performance Co-efficient (EPC) and Carbon Performance Co-efficient (CPC) must be less than 0.302 and 0.305 respectively.
The smart way to achieve this standard is the fabric first approach. We need to use more thermally efficient materials and reduce construction cost by designing buildings in a way that addresses thermal bridging and improves airtightness.
Single leaf thin joint construction could have been designed for nZEB. The use of aircrete thermal blocks in conjunction with thin layer mortar and external insulation can achieve exceptional U-values and address thermal bridging and airtightness almost by default. All this whilst eliminating the risk of interstitial or surface condensation.
nZEB friendly? Yes, but it offers more than that. The comfort factor is, for the end user, one of the key selling points. A well-designed, nZEB compliant house consisting of thin joint masonry construction will be more comfortable to live in. The thermal mass of the masonry walls will help regulate temperatures giving a much more constant temperature throughout the day and night, whilst saving on heating and cooling requirement when compared to lightweight framed construction.
That ‘chill’ feeling we get from a poorly designed junction with low surface temperature will be no more. The health implications from mould growing on cold surfaces or invisibly within the structure will no longer be a concern.
As if that wasn’t enough, aircrete thermal blocks built with thin joint mortar are stronger than traditional blockwork. A recent study had shown that 200mm Quinn Lite B7 block built with thin joint mortar is almost 3 times stronger than a 350mm wide traditional cavity wall when assessed under typical domestic loading.
If we want better quality housing, and we do, the argument is certainly strong.
Crunching the numbers
With the list of benefits achievable using thin joint construction, you’d be forgiven for thinking this will blow the budget. On the contrary. When we compare the costs to timber frame housing, it’s significantly cheaper. For a pair of typical semi-detached houses, single leaf thin joint masonry will save you around €6,000 on build costs. This does not include savings which can be made by calculating the thermal bridging factor and subsequently reducing the amount of renewables or indeed insulation required elsewhere in the build, which will easily exceed an additional €2,000.
Yes, it costs slightly more than traditional masonry wall construction, but when we take the time and labour savings into account, and the quicker completion of the house, the gap becomes relatively narrow. It’s a very small price to pay for a significantly improved quality of build.
Adopting thin joint in Ireland
On paper, thin joint looks undeniably strong. So, what does it take to facilitate adoption in the Irish construction industry?
The reality is that the ‘fundamental change’ is not so fundamental after all, given that it does not require a radical shift in building practice, or the complete re-training of Irish tradesmen. The practice of building thin joint block walls can be quickly adopted by willing builders, given that it relies on the skills already in place.
The bigger challenge, as is often the case when we’re asking for change, is changing minds, and changing habits.
We’ve recently introduced SIMS by Quinn, a construction system which utilises thin joint technology and single leaf Quinn Lite thermal blocks, externally finished with an NSAI certified external insulation system and internally finished with plasterboard on dabs or wet plaster.
The solution delivers on all the benefits discussed: faster, better fire performance, better thermal properties, airtight, and cheaper than timber frame. We’ve been working with a number of Contractors and Architects on their plans, and SIMS houses will be in construction within weeks, marking the first steps towards better housing, faster.
Tags: Aircrete Blocks, Architect, Construction products, nZEB, Quinn Lite, rapid build construction, rapid build housing, rapid build Ireland, SIMS SIMS by Quinn, Thermal Bridging, Thin joint, thin joint blockwork, thin joint construction, thin joint masonry construction, thin joint technology, timber frame