One of the key decisions we had to take on our build was what method we should use for the construction. There were three major options: traditional brick and block; timber-frame; or SIPS (structural insulated panels). We fairly rapidly dismissed the traditional brick and block method on cost, time and environmental impact. We took some time to decide between Timber Frame and SIPs.
Initially we were attracted to the SIPs approach. As we are trying to build to near Passive House standards there is a clear appeal in using pre-insulated panels that are put together in a factory environment, with the precision fitting on site significantly reducing the risk of air bridges. They are load bearing so obviate the requirement for beams and supports and are thinner than other methods of building so provide up to 10% more space within the house. Also in the right hands they go up very quickly, (once delivered on site the shell can be up in 7 days), and provide walls and roofing in one package.
However a key consideration for us on our site is access! Our property is down a narrow lane and we quickly realised that we would not be able to get regular sized SIPs panels to the site – this would mean using smaller panels which impacted on cost, speed of construction and potentially air tightness.
Another issue is that SIPS do need to be kept dry and given the incredibly inclement weather we have been experiencing since the build started this would have been a major challenge and concern. This doesn’t mean that they cannot get wet at all, but the relentless, endless rain we have experienced over many weeks would likely have resulted in a delay to the project.
Also with SIPs as they are fully constructed off site all the channels for plumbing, wiring, and windows and doors have to be done at that point, they are therefore a fairly inflexible building system. It is very difficult to make changes to apertures and services once the SIPs have been manufactured.
So we then looked at timber frames – initially factory manufactured that could be produced off site and then delivered and constructed in a few days. Timber frames offer some of the same advantages as SIPs. Provided they come from a sustainable source they are environmentally better than traditional builds. They can be put up relatively quickly compared to traditional builds. If they are properly insulated and sealed they can give the same thermal performance of SIPS. However on the downside factory manufactured timber frames allow for little flexibility once done and again we came up against the site access issue.
When Phil of HM Construction https://www.hmconstructionuk.co.uk put in his quote for the job he said that he would prefer to build the timber frame on site. He confirmed that his team could do this within the same timeframe that it would take to get factory frame produced and erected on site.
This method is known as “stick built,” as the building goes up literally stick by stick. This had immediate appeal for three reasons. Firstly it dealt with the access issue as it is a lot easier to get the loose timber delivered up the lane rather than large pre-built frames. Secondly it meant just one contractor managing the job from end to end – laying the foundation stones and constructing the frame, so reduced risk of errors, miscommunications and conflicts. And finally it does allow for some flexibility in design as if we found anything that looked completely wrong once erected it would be possible to make changes if absolutely necessary, though this is not desirable as it impacts on costs and timeframes.
Many of the modular timber frame companies are critical of stick built houses particularly concerning quality assurance of the workmanship. Tony our designer was well aware of these issues and before we agreed to let HM Construction use the stick build approach we went to see a building they had constructed using that method. This satisfied us as to the quality and attention to detail of their work. Owing a lot to the fact that they started as a Carpentry business then moved into major construction; so their roots and skills are ideal for stick built construction.
Suffice to say we are delighted with our choice. The frame has gone up incredibly fast – the ground floor was in place in just over a week and we have been informed by Phil that the first floor will be finished before the break for the Christmas Holidays. We literally can see our house rising out of the foundations before our eyes, it is very exciting and impressive.
What is equally impressive is the team putting it up. They have worked in all weathers, every day. Neighbours have commented on how diligent they are and cheerful despite the adverse conditions. They really are brilliant.
So as 2019 draws to a close our build is well on its way. The New Year will see new challenges and new decisions as we drill for water, finalise all the minutiae of details that are required for fitting out the house, fit the windows and doors and decide on which Solar PV system to use. But for the next few weeks I will be taking a break as I go to visit dear friends in South Africa. So I would like to take this opportunity to send you all seasons greetings with a message from the TWO TOMs!