Diary of a self-builder – Part 10: Creating an airtight oak frame home

August 17, 2017

Last month in ‘Diary of a self-builder – Part 9’, Mark told us about fitting his joinery and his on-going issues with the utility companies. This month Mark talks us through the all-important task of creating a well-insulated home.

Once the main utility services (water and electricity) were in and the trenches covered, I had a permanent electricity supply that was fully metered and unique to our house.

Severn Trent had given me a date to get the permanent water supply in place, as the existing one needed to be upgraded to a 32mm pipe. Unfortunately, this meant another road closure and dig; which meant we would be in the dog house with the neighbours again. It’s such a shame the providers cannot liaise and work alongside each other to ensure that there’s only one road closure and one level of disruption and cost to all.

The only thing that was left to consider was how the BT broadband line would get to the house. I was not keen on having overhead cables which meant I would need to dig yet another trench soon!

I was feeling a bit nervy about all the services and drains running underground. I decided to map out the location of each run (as far as is practicable) so I didn’t accidentally break through any pipes.

Our home emerges

I was really pleased with the full effect of the contemporary windows and doors; I think the grey tone looks great against the beamwork, and will look even better once the oak starts to silver down. My obsession with the notion of combining oak, an age-old building material, with modern fabrics and finishes came together nicely. I received comments from people saying that the emerging look was great.

Along with the design of our home, the thermal efficiency and air tightness were key elements that dictated the overall ethos and specification of the build. As Julia and I have experienced living in an old house where there’s always something to repair or make good, it was very important to us for the property to be as low maintenance as possible.

I was determined that the new house would be trouble free, simple to look after and straightforward to keep clean and tidy – so we have no unnecessary nooks and crannies, just wide open spaces to live in and enjoy.

I used Marley Eternit’s Cedral Lap weatherboard in several places; it has a grey hue and requires no maintenance because it is made of fibre cement. It will never rot and comes pre-painted, too.

For the balcony decking, I managed to source a recycled extruded plastic product from Eco Systems, which has a wood grain effect to it on one side and a more traditional grooved finish on the other. It was really simple to fit with a rather nifty T-shaped section that creates an even gap, allowing for simple screw fittings. This is also maintenance free and is quite easy on the eye.

The balconies coming off all three bedrooms are made from durable stainless steel posts and brackets with toughened glass panels in-between. We’ve named one of them the ‘G&T balcony’ in eager anticipation of our lifestyle to come.

Fitting the insulation

I dreaded the insulation phase from day one. I have been anxious about it for two reasons: the first is the cost outlay; the second is the pure drudgery of the installation process.

I shopped around very hard for the best value product to meet the initial design-stage performance set out in the Standard Assessment Procedure (SAP). I chose Xtratherm, who gave me fantastic support and advice about their range and managed to break down in simple English the various benefits of their product.

Julia and I carried out the unbelievably tedious work of cutting and fitting the insulation. It was a dirty, messy, smelly task and even wearing masks and goggles, the dust that comes off during cutting is horrible stuff. When it gets in your eyes it is agony. I am slightly asthmatic and also suffer from hay fever, so it played havoc with my allergies.

Insulating the ceilings was by far the worst bit, where I needed to fit 120mm-thick insulation into the gaps between the rafters. The entire second floor is vaulted to show off the oak detail, so there is effectively no flat ceiling anywhere. There are four major valleys in the roof, which meant a horrendous number of angles and compound cuts to make in the insulation. I then had to try to make it fit snugly between the rafters.

I was obviously working at a fair height up at the ridgeline and in the middle of summer the heat in that area of the house was intense. You can probably imagine the sweating, a runny nose and dust floating in the air was not pleasant at all.

The real killer was actually the sheer amount of time it took. I could be at it solidly for a day, up and down the ladder and felt there wasn’t any progress being made, so it was quite demoralising stuff. I couldn’t wait to at least get the ceilings done; the straight walls and flooring were a doddle after this.

A tight seal

Alongside this nasty element of work came the task of getting the build as airtight as possible. This was also painfully slow and required a great deal of care and attention. You only have one chance to get this right so it has to be done well.

Under normal conditions it would have been probably correct to have had a full air tightness test carried out at this stage of the process so we could detect any leaks and fix them. The problem was I hadn’t had the glass fitted to the doors and I didn’t want to put the panes in at the front or back in case they got damaged. So there was no point in testing this element at that point.

Julia got stuck into the job of installing and taping up the specialised breathable membrane supplied by Pro Clima. I told her it’s just like wrapping up my birthday present, only from the inside out, and I did keep reminding her of the money we’ll save on the heating bills.

One very upsetting aspect of this work is that there’s an unbelievable amount of wastage. It is estimated that as much as 30% of the material can be lost. We spent £10,000 on our insulation so if this is correct I threw £3,000 away. And that’s not all, it cannot be considered household waste so we couldn’t just take it down to the local refuse depot. I apparently needed a special license or I would have to pay a registered waste disposal operator to take the offcuts away for me.

I really think it’s time that the insulation manufacturers get to grips with dealing with the reuse or recycling of the offcuts. It’s an astounding waste of money and I just cannot believe there is no other use for this material. I understand Kingspan has announced a scheme for taking the remnants back, but I have no idea how it could work economically – unless they are going to make a charge for this service. Either way it’s an area of great concern; if this amount was wasted on our house build alone, I can’t imagine what happens on a nationwide scale.

Julia and I looked forward to the next phase; which was the first fix electrical and plumbing work. It was at this stage we started to make the internals our own. I hadn’t even put up the stud walls yet, so we were still imagining the room spaces, but we couldn’t wait to get on with it.

Next month Mark and Julia prepare for the first fix phase and start to imagine how they will live in their brand new home.