When you set out to build your dream home, the building method you choose may not be the first thing you think of, but the construction method will affect virtually every aspect of the project. From cost, to build time, to energy efficiency; each building method has different implications.
Here, we outline some of the various systems used in construction and what you should consider before proceeding:
The most common method of home construction in Ireland remains the standard masonry system, consisting of two rows of blockwork with a cavity in between. Insulation can be built into the cavity, but it is more common nowadays for the space to be pumped with bonded beads. Cavities have grown bigger over time, with 200mm-plus now being used.
The pros are it economical, tried and tested, good thermal mass. But it’s on-site approach means that it can be forgiving of discrepancies in foundations. As the dominant system there are loads of firms and tradesmen familiar with it, and – with training – ambitious self-builders can also get stuck in.
The Cons are its slow. Houses are physically built on site, meaning that this route has a longer ‘on-site’ build phase, which can cause inconvenience to neighbors or be liable to theft of vandalism. Slow construction means process is largely weather-dependent. Requires detailing and attention on site to ensure airtightness. Takes time to dry on site and is affected by bad weather. It also requires load-bearing walls, so open-plan designs need to be carefully planned.
Thin-joint blockwork is a variation of brick and block, that uses just 3mm of mortar. It’s a specialised system that makes for a quick build. It has to be accurately built because it doesn’t use conventional 10mm mortar beds — hence the name, thin-joint.
Modern Methods of Construction (MMC):
The term MMC can be used to describe a whole range of building methods, the uniting factor being that they are not traditional. Other terms that are used for MMC include:
industrialised or system building
They generally involve some use of new materials and a large element of factory production. Let’s talk about some examples:
1. Timber Frame
Timber carcass produced in a factory and assembled on site; external wall finish and roofing completed on site. The second-most popular route, built of wood products that act as the superstructure. This could be traditional post-and-beam or modern interpretations, such as Glulam. This is a specialist trade, built off-site in a factory to an agreed design, usually in a matter of weeks. Changes are costly once commissioned, and there’s little scope for self-builders to work on the actual structure. As it’s prefabricated off-site, the frame is erected on-site in a matter of days, and the erection is all taken care of by your manufacturer and contractors. Modern glued wood is enormously versatile, meaning it can create open-plan spaces and interesting designs with ease. The outer skin can be finished in pretty much any cladding finish – brick slips to create the look of brick, render, timber or tile. However, the foundations must be perfect, and there’s little scope for serious modification once built.
2. SIPs – Structural Insulated Panels
A system that uses panels made of a sandwich of OSB (oriented strandboard) bonded around an insulated centre. These are precision made in a factory, making a quick on-site build, and the structure is quick to erect and needs very few load bearing walls.
SIPs can be used to make walls, floors, ceilings and the roof, and they maximise loft space as there’s no need for roof trusses. While a bit more costly than conventional timber frame, you save on labour costs. The route also offers excellent air-tightness and high levels on insulation, but again this requires experienced tradesmen and precision engineering. Foundations have to be faultless, too.
The exterior can be finished in a choice of cladding finishes to create the look you want.
3. ICF – Insulated Concrete Formwork
Like the famous building blocks kids play with, ICF is made of large hollow blocks that stack to create cavities that flow through the entire structure. Typically these are made of expanded polystyrene. This insulated formwork is then pumped full of concrete to create a robust structure with great insulation values. Self-builders can easily get stuck-in with a bit of training from your supplier, but plans must be adhered to, as it’s very hard to change once the concrete is poured. It’s a quick build system, but not that common and your foundations must be spot-on – mistakes are costly to remedy. Again a range of cladding finishes are available.
4. ‘Natural’ build materials
If a sustainable, eco-friendly, self build is important to you there are many other build routes with greener credentials. Some of the alternative construction methods include Hempcrete, green oak, cob, steel frame, straw bales, rammed earth and log building. Many are niche areas but each year the numbers of self builders incorporating at least some of these methods and materials increases.
The informative presentation, ‘Modern Methods of Construction (MMC) & Eco-Building‘, explains the pros and cons of the main methods of construction.
5. Passive or Passivhaus
Not so much a build route to the structure, building a passive house is about creating a home that’s got lower running costs due to the way its constructed. Consequently, attention is given to the orientation of windows to capture solar gain in summer with overhangs offering shading in the summer, as well as very high levels of insulation. They typically have mechanical heating and ventilation systems that circulate air throughout the house, reusing heat rather than venting it outside, and because of this they need to be extremely airtight.
If you have any queries on the above or would like further advice on building materials for your new build, please contact me here.