Selfbuilders need to think further ahead than ever

It’s not often that a major Hollywood movie combines two of my abiding passions – science fiction, that is, and housing – but that’s exactly what the recent Matt Damon vehicle Downsizing achieved.

It really is about moving from one barely affordable house to another on a completely different scale, thereby making dramatic cost savings. But, being Hollywood, it’s not just the house that changes scale. It’s the occupants, too.

Thanks to a vague but convenient process discovered by Norwegian scientists, Mr Damon is shrunk to a height of just five inches. By selling his small, cramped, heavily mortgaged family home he is easily able to afford a huge, multi-bedroomed, chateau-style mansion – mainly because it’s the size of the average doll’s house.

Miniaturisation would certainly do a lot to resolve Britain’s ongoing housing crisis. But in the non-Hollywood world the nearest we get is the steady shrinking of the average developer’s property and the rise of micro-apartments, aimed generally at young singletons.

Both, of course, are good reasons to consider building your own home. But how exactly should you build it?

The question is likely to be more complex today than in previous decades for at least two good reasons. One is that the time you spend in your new home may well be longer than you plan. Declining incomes, rising property prices and high stamp duty mean that moving house every seven years or so – the traditional average at the turn of the century – is either financially impossible or wildly uneconomic. In other words, one of the main reasons for self build – jumping a rung or two on the property ladder – is far less important than it was. The pendulum has swung towards the second main reason for self build: building a ‘forever’ home, traditionally prompted mainly by retirement and downsizing.

The other major factor to consider is climate change. Whatever the causes, the weather is becoming more extreme, and more unpredictable, and we need to take account of that in the way we heat – and cool – our homes.

These are the issues examined in a recent report by the National House Building Council (NHBC). The UK’s best-known provider of warranties and insurance for new homes, it also sets the bulk of the UK’s building standards.

Entitled Futurology, the report looks 30 years into the future to judge what the homes of 2050 might be like. It also takes into account a handful of basic statistics. They include the increasing numbers of people currently living alone (up 51 per cent over the last 20-odd years), of young adults living with their parents (now one-third of 20- to 34-year-olds) and of people aged over 85 (likely to double by 2041.)

Flexibility

So what recommendations does it have to make your build 2050-ready? Flexibility is the key word in future-ready design. A layout that suits a couple or a young family today should be adaptable to cope with adult offspring who can’t afford to leave and, perhaps, even their offspring. Multi-generational homes, once the norm in western societies, are likely to become much more common – and not just out of financial necessity. Other generations can provide childcare and care for the elderly, as well as companionship, plus the benefits of multiple incomes.

In practical terms that means the ability to create areas with specific functions as and when they are required. Think home offices, quiet spaces and even self-contained accommodation for teenagers, the elderly or lodgers.

On large plots extensions into the garden can often meet that need most easily. But on an urban site where space is likely to be more limited, and planning rules stricter, building those options in at the design stage is usually more sensible.

The report offers townhouse designs over three and four storeys, sacrificing much of the garden space – a process already underway with the growing popularity of garden studios. Instead, outside space is provided by either terraces on the upper floors, a small courtyard at ground level, or both.

All the internal walls are lightweight partitions which can be removed or rearranged. To make this easier all pipework and wiring runs through the external walls and a central core, which might include the staircase and an adjacent space on each floor. This space is large enough to take a small one- or two-person lift, which can be installed later if needed. Until then it can act as a cupboard or storage area.

Meanwhile each floor has either a bathroom or shower room with toilet. One or more of the upper floors can also contain the plumbing and electrics for a kitchen, enabling it to become self contained. One design featured in the report adds an external staircase rising from a courtyard to the top floor, allowing it to be entirely separate from the rest of the house, if needed.

As to the weather in 2050, the report assumes heavier rainfall, more heatwaves, storms and drought and also unpredictable fluctuations in temperature – ‘summer days’ in winter, and vice versa. To combat overheating, it suggests ample exterior shading and secure ventilation at roof height – ideally over stairwells – to allow excessive warm air to rise through the house.

It also recommends careful thought before choosing masonry construction – still Britain’s favourite – since thermal mass is slow to heat and cool. Underfloor heating, too, with its slow response times, may not suit a volatile climate.

On the other hand, those effects can be mitigated by using thermal stores such as large water cylinders or ground-coupled heat exchangers. These are tubes, either empty or fluid-filled, buried over a metre deep in the ground where the temperature is around 10C throughout the year. As a result they can be used either to dump excessive heat or draw cool air into the house.

And if all that sounds a bit high tech, it’s how ground source heat pump central heating systems work.

December 2018