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The benefits and drawbacks of pre-fabricating your dream home

Have you considered using pre-fabrication as a method for building your own home?

Germany has been at the forefront of pre-fabricating home design for over 50 years (https://www.weberhaus.co.uk/) and the benefits are very German; time efficient, quality guarantee, energy efficiency guarantees. These advantages are also useful to British self-builders. Anyone who has spent time on a UK building site in winter will testify to the stress caused by weather delays and the impractical nature of working knee deep in mud. With pre-fabrication there is no need to worry about weather conditions setting you back or indeed supplier delays, you can have your dream home within a few weeks.

If you are building on a site such as Gravenhill (self-build site in Bicester) then you might find pre-fabrication offers cost and time certainty in achieving the 24 month build deadline.

We are keen to work with self-builders looking at the pre-fabrication route. We are good at working closely with pre-fabricators to ensure that you get the design and the home that you really want and for the price that you can afford.

Pre-fabrication options

There are quite a few different pre-fabrication options now available in the UK. These can be quite confusing and hopefully the next few paragraphs will ease your understanding:

Hemp, lime and timber frame prefabricated panels

Greencore closed panel system using hemp, lime and timber frame to create a breathable construction

Complete pre-fabrication (or closed panel timber frame system)

Everything is manufactured off site and arrives on a lorry. It is a timber frame system, originally from Germany but now also found in the UK (Greencore Construction, Modcell), including; external cladding, doors and windows fitted, ducting and service voids. The heavy panels require a crane so this method not suitable for a poorly accessible site. Sometimes also these systems include foundations (e.g Danilith and Greencore Construction), other times this is contracted separately.

Super structure pre-fabrication (or open panel timber frame system)

Only the walls and roof structure are built off-site in a factory, external cladding is fitted on site, as are windows, doors, ducting, plumbing, electrics. These and the rest of the trades are managed by the self-builder.

SIPs (Structurally Insulated Panels)

An American idea that made its way over to the UK in the 50’s. These are panels that look like an insulation sandwich. Not really timber frame although the ‘bread’ is usually formed from OSB (made from waste timber) or plywood panels. Not so easily mortgageable (see below).

Oakframe construction

Large timber structure made off-site and then walls and roof are wrapped in SIPs or a more natural, breathable insulation and cladding layer. The oak frame is exposed internally creating a more traditional and characterful appearance. E.g Oakwrights and Carpenter Oak

Concrete insulated panel system

Heavy panels, requiring crane erection, with pre-fitted brick/render/timber/flint cladding. E.g Danilith

Insulated Concrete Formwork (ICF)

Speeds up on site masonry construction. Not pre-fab but some companies think it saves up to 25% of time on site compared to traditional masonry construction (HB&R mag link reference).

Mortgageable straw home

Inside one of the first straw bale homes to be mortgageable in the UK (by Modcell and White Design).

Mortgageability

A timber frame pre-fabricated home will ensure that you have access to any high street lender, if you want to use SIPs you will need a specialist lender with less competitive rates. If you can buy your plot in cash you can get a mortgage based on the value of the land which gives you access to much cheaper loans.

Sustainability benefits

Off-site construction results in less construction waste, any left over materials can be re-used in the factory instead of going to land fill. But this needs to be offset with how many miles the wall and roof panels have travelled. Though there are now companies manufacturing in the UK (Scotframe, Dwelle, Boutique Modern, Modcell and Greencore). Modcell use ‘flying factories’ to literally factory build within a few miles of your site using local farm buildings and straw. Very high standards of energy efficiency and airtightness can be achieved, this, combined with a heat recovery ventilation system, will ensure a warm, healthy, fresh air environment. Only the ‘complete pre-fabrication system’ will come with the heat recovery system installed, this will need to be designed and installed by professionals if using one of the other systems.

We at CNA are keen to work on pre-fabricated dwellings with strong sustainability credentials. We believe a breathable system is best (such as Modcell, Greencore, Oakwrights or Dwelle). Timber is a breathable material and it makes sense to use breathable insulations with it. There have been issues in America whereby poor airtightness detailing has caused SIPs panels to go mouldy in parts. Until everyone is really super hot on airtightness in the UK, we feel it is safer to use breathable materials (and it is better for the environment).

Modcell straw bale home

The thickness of walls inside a Modcell and White Design straw bale pre-fabricated home in Bristol

 

Benefits of pre-fabricating your dream home

Cost certainty and time saving on site (British weather is not an issue), guaranteed airtightness and energy efficiency, high quality design. If using a UK pre-fabricator, the embodied energy of producing your home will be very low and you will be creating a true eco-home. Costs are reducing as more pre-fabricators have factories in the UK and custom build sites such as igloo’s Trevenson Park in Cornwall are increasing the demand for pre-fabricated homes. Your finish date for a watertight shell will be a certainty and if you go for the full pre-fabrication method, your move in date will be certain as well. This is a great asset when paying rent or living in a caravan on site.

 

Downsides of pre-fabricating your dream home

It can cost more (but you have much more predictability about these costs, rather than waiting on site for problems to occur, or for bad weather or supplier delays). It is expensive to ship panels from the continent, but these days there are a few options for UK pre-fabricated homes (see above under sustainability).

Once the design is fixed, it is very difficult to change things on site, windows can’t be moved a bit to the left or right or sizes changed. Walls can’t be moved (unless the pre-fab element is just outer walls). Additionally some pre-fabrication types work best with certain external cladding such as timber, render, stone. This can be an issue where planning requirements dictate a certain material is used externally. This is why it is a good idea to have an architect involved to really understand what your dream home entails and how it is best realised. Pre-fabrication companies offer fantastic benefits, but sometimes their designs can restrict your aspirations, or they are a bit too ‘standardised’. An architect can push these boundaries with the pre-fabrication firm, ensuring you realise your dream home for a cost and timescale that works for you.

August 22, 2017

The benefits of using an architect on a Gravenhill self-build or elsewhere

self build benefits of architect

Thinking of building a Gravenhill Self-Build? Here’s how to save money and reduce stress…

It’s finally happening!  You’ve found your plot, bought a hard hat, and watched every episode of Grand Designs twice over.  You’re ready to build your own house, the way that you want.  You have a clear vision of how it will be, so why appoint an architect?  Doesn’t self-build mean you do everything yourself, controlling every aspect of the project down to the doorknobs?

Well, that’s one way of approaching this task, but an architect can actually be an invaluable guide through the Gravenhill self-build process.  A professional architect will help you to get the best quality home for your budget. They will identify potential pitfalls, and be an important point of contact for your project team, co-ordinating designs from many consultants – structural engineers, ventilation design, window manufacturers, etc, etc.  Even those self-builders with lots of experience in the construction industry benefit greatly from employing an architect to work on their build – for example this client, an engineer who has been working with CNA to realise his dream of an eco-house for his family.  He has said:

Just a quick note to say that we have had the below positive response from SNC Planning with regards to our proposals. And without your valued input through the process we wouldn’t be in this position, so thank you very much….the models and proposals have been excellent and really changed the way we’d been looking at some of the aspects of our design.

An architect will help self-builders to make the most of something like a Graven Hill Golden Brick package, turning the bare bones of a project into a bespoke home within tight budget and time constraints.

 

self build benefits of architect

Cost

Budget is the defining element of any project, and getting the most out of it can be the difference between a dream home and just an expensive pile of bricks.  An architect can find you the best value for money in terms of materials and labour, and also reduce the running costs of your building in the future through good design.  A product such as a Graven Hill Golden Brick is a good starting point for estimating the cost of a self-build, but, as anyone who has flown with a budget airline knows, what starts out as a clear and transparent set of costs can all too easily become a quagmire of optional extras and hidden fees and charges.  An architect can help you anticipate, reduce and avoid these potential costs, and help you to decide what is worth spending money on and what is not. One self-build interviewee stated that without an architect, she could not have afforded her dream home.

 

self build benefits of architect

Time

In the grand list of self-building headaches, time comes a close second to cost, and there is of course a huge overlap between the two.  In the case of a package such as a Golden Brick at Gravenhill (self-build site in Bicester), the issue of time is brought sharply to the fore with the looming 32 month deadline to get a home built.  An architect can speed up the process of design itself, as well as streamlining the planning and construction stages.  It is our job to always be thinking one step ahead and making sure that the design will cause minimal problems in getting through planning and building control, and also on-site.  Our industry knowledge can also speed up decision making for you, reducing or eliminating the need for you to spend days (or weeks!) researching products or legal requirements for the project.

 

Quality

Quality is something self-builders have a large amount of control over.  This can be both a blessing, as you do not have to compromise on things that are important to you, and a curse, as the responsibility for making the correct decisions can result in a great amount of pressure and stress.  An architect, especially one based locally, is your gateway to an established network of reliable and recommended tradespeople.  Over their years in the industry, we at CNA have done the groundwork of building invaluable relationships with tradespeople, suppliers, planners and building inspectors, that you can then take advantage of.

Getting the design right

Another major influencing factor in the quality of a build is the design itself.  This is undoubtedly where architects come into their own, and where their years (and years and years!) of training are most evident.  Your architect can interpret your individual needs and come up with solutions that suit your lifestyle that you may not have even considered yourself.  They can also work out ways of fitting your requirements into restrictions such as a strict Design Code that may apply to your plot.  A predefined material or formal palette does not mean your home cannot be a bespoke expression of you.  Good design means that your home will be comfortable, safe and secure, meaning you are less likely to need to spend money on changes in years to come.  Once your house is built you will truly be able to settle in and relax.  It may be a cliché, but happiness and wellbeing are priceless, and your home is a crucial part of building a healthy personal environment.

 

self build benefits of architect

Eco-design

A house that has a minimal impact on the environment is something we should all be striving for.  Eco-houses run more efficiently, more cheaply, are healthier for their inhabitants, and create less problems such as damp and poor air quality.  Good design ensures that an eco-house need not cost more than a conventional one, and environmentally friendly features can be tailored to your lifestyle and the way you will use the house.  In fact, an energy-efficient house should eventually free up spare cash in the long term (perhaps for more home improvements!), so getting this right at the beginning can mean you reap the benefits in terms of savings for years to come.  An architect who specialises in eco-design like Clare Nash can help you to meet and surpass minimum energy requirements, such as the Fabric Energy Efficiency standards Graven Hill self-builders must adhere to.

 

Decision making

Decision making can be a daunting and energy-sapping aspect of the design process.  An architect can guide and inform you, as well as providing specialist services such as visualisations of your design options.  These can help you to decide what you really want, and persuade planners and investors of the merits of your proposal.  You can discuss all aspects of the project with your architect before you embark on it.  This will give you the time, foreplanning, information and expert insight to put your mind more at rest than if you had to make important decisions alone.  Even just an hour discussing your your plans with a professional can make a marked difference to your approach and peace of mind.

 

self build benefits of architect

Project management

Housebuilding is a risky business.  With so many things to think about, juggle, and schedule, having an architect to manage the process for you can greatly reduce your risk of going over budget and over time, and hopefully preserve some of your sanity during what will be an incredibly busy time!  When it comes to your home you are considerably emotionally invested, and having somebody who can take an objective overview can help to keep the project balanced and in perspective.

 

An architect such as Clare Nash can work with self-builders to bring out the best of their ideas, enthusiasm and motivation, as well as streamlining a complex and tiring process.  If you are an interested self-builder, or a potential one, please do get in touch with Clare Nash Architecture Ltd for a friendly chat and to see what we can do for you.

What can the UK learn about housing from examples around the world?

Katie Reilly takes inspiration from Chapter 5 of Clare’s book

vernacular housing bolivia

Centro Lak’a Uta in Bolivia: a case study in Clare’s book

The UK’s climate can be challenging to cope with due to the daily surprise of rain or shine (mostly rain!) but imagine building in an environment of extreme temperature differences, even between day and night!

In some parts of the world, ancient traditions are still practised and very much influence people’s everyday lives today, from religion to social norms. When considering designing a contemporary vernacular in areas of active rich cultural history such as those in Chapter 5 of ‘Contemporary Vernacular Design: How British housing can rediscover its soul’, it is important to take the time to understand what is important to these communities in terms of housing apart from the structure itself. What religious needs do they have? How are the communities living arrangements structured? Do they prefer to cook inside or outside? What are their social norms? e.g. the relationship between men and women or entertaining? What is their typical livelihood and does this affect their living arrangements? How do all these elements affect a community’s interaction with their housing?

While it is true that for the first time in history more than half of the world’s population live in urban environments, there is still a percentage that do not for a variety of reasons; their livelihood being one of them. As often found in traditional construction, structural and environmental techniques have been refined over many years to suit specific cultural and contextual needs. However, changing global dynamics like climate change and aspiring to Western ideals can put pressure on traditional ways of life, including housing. Therefore, in order for rural dwellers to retain their cultural heritage and practices their existing housing construction may need to be adapted and a new contemporary vernacular formed that better responds to evolving contexts consequence of these changing global demands.

vernacular house sago leaf bamboo

A vernacular house in Papua New Guinea with sago-leaf roof and bamboo walls

vernacular papua new guinea climate control

Clare’s book explores several case studies where time has been taken to identify the questions posed above and, in some cases, using this information to systematically analyse existing construction methods and materials. Elements in each case study that respond positively structurally and environmentally to their local climate, landscape and community needs have been have been highlighted. For example, adapting traditional adobe construction by adding steel formulates a contemporary vernacular that is better equipped in responding to earthquake prone areas thus supporting the future of its inhabitants. Understanding that certain materials like adobe can be interpreted as poorer can be difficult for outsiders to a community to comprehend as it has positive attributes for responding to extreme climates such as great strength and thermal mass. Therefore, how can a programme integrate a material thought of as such be translated into housing that is flexible in supporting more Western ideals and local ideas of wealth?

Australia passive design

Passive design principles, as used by Lindsay Johnston in Australia

passive design principles shade tree

Something that is clear from Chapter 5’s case studies is the importance of the future of housing projects in areas such as those described. A housing programme would be an injustice to the community if it did not consider the building’s longevity and how it will impact the lives of its inhabitants. Arguably, some of the most successful projects are those that include the community in the building process as these widen participants’ skillset and allow a sense of ownership to develop, enabling locals to continue to construct the new housing vernacular in the future. Programmes like these can provide employment opportunities and integrate new housing types into their appropriate contexts.

Clare’s book inquires how British housing can rediscover its soul. The case studies explore how using vernacular techniques for environment and structure (like adobe, sun orientation and cross ventilation) over more western ones (such as brick/concrete and air conditioning units) can enrich housing in so many ways. Be it culturally, for well-being, reducing energy consumption and most importantly, encouraging people to live as they would like to. The book is not saying that in Britain we must build in adobe, avoid using modern technologies and live on zero energy (although low energy is something to strive for!); rather in taking the time to understand the context, the community, history and local traditions of a place, Britain too can enrich their housing design and make it locally relevant and nationally proud again.

by Katie Reilly

CNA visit to Straw Bale House by Sarah Wigglesworth Architects

Recently Clare Nash Architecture Ltd. (CNA) visited the famous Straw Bale House in North London designed by Sarah Wigglesworth and Jeremy Till. With sustainability and eco design at the centre of CNA’s design approach, we were excited to be given a tour by Jeremy himself who explained how their pioneering project came about.

The team met outside the house-come- office’s tall wicker gates at the very end of Stock Orchard Street in London. With the railway on one side and Victorian terraces on the other, a building on gabion stilts with sand bags on one elevation is not quite what you would expect to find at the end of the road!

Luckily it was a dry (if a little chilly!) day as the tour started outside, with Jeremy explaining how the design concept for the Straw Bale House was developed through Sarah and him sharing stories, before any drawings were even started. Once the design was established through drawings the next challenge was getting it through planning, which was perhaps aided by one of Jeremy’s anecdotes involving a party for local residents. The building is well known for being the first straw bale house to be granted planning permission in the UK, however there are many other materials at play here including sandbags and stone gabions which certainly challenged ideas on conventional building materials at the time. The talk outside lasted for about an hour discussing structure and sustainability.

Turning the corner around the house it was a pleasant surprise to find their garden, a surprisingly green and spacious area for central London. As lovers of fresh vegetables, it was great to see what crops they were growing in their garden and to hear the clucking of chickens too! Mid-construction decisions led to only having a back door which is now the front door and works well as it encourages you to walk through the garden before entering the house.

Walking inside and up the stairs I was not sure what to expect of a space which is both living and office, shared and private. However, the top of the stairs greeted us with a warm open plan living space that was cleverly divided into functional spaces; making sense of the unusual floor layout which was organised around an organically shaped larder inspired by Malawi cooking ovens. The use of natural wood and exposed white painted steelwork could have had a cool industrial feel to it but was complimented by splashes of warm orange furnishings and large amounts of glass allowing natural light to flood the space enhancing the feeling of homeliness. One of my favourite areas was the kitchen which was again homely and quirky too as each item seemed carefully considered, perhaps handcrafted, all the way down to the papier mache lampshade suspended over the table.

A fairly large group were on the tour with us but after admiring the first floor, we ascended the (perhaps not quite building regs approved!) staircase into the tower. Lining the stairs were shelves and shelves of books which seemed to change in levels of architectural relevance the further up you went. So at the bottom were architectural text books while at the top, nearing Jeremy’s office, were fiction books and novels. Having a library like this might get tiring in reality but as a visitor it was a very charming idea!

On our way out we popped into Sarah Wigglesworth’s attached (Quilted) office where she was working. It was an impressive space, both organised and bright and surprisingly quiet despite being on the railway track side- the sandbags must be doing their job!

Although the project is known for having challenged ideas of structure and materials in terms of sustainability, it was very interesting to hear Jeremey Till say that the construction methods and material composition are actually not that sustainable in the context of what is possible today. Technology has moved on since the house was originally built; even the double glazing is no longer as efficient as it could be!  Nonetheless, the choice and composition of the interior materials and spaces has a certain quality to it that, while you could probably Google ‘Sarah Wigglesworth House’ or something similar; would just not be the same as experiencing in reality.

 

 

 

Vernacular self-build today

DSCF7269DSCF7386I presented a talk at Oxford Brookes University today on the subject of my masters (How Vernacular Technologies can be used in Modern Sustainable Housing Design) and how I apply it to my work today.

Does vernacular self-build have a future?

I spoke about how vernacular building is a time rich product and it has been written that as such it is no longer sustainable. In developed countries it is only the rich who have the money to pay others to self build to their design, in developing countries, only the Campesino’s (farmers) have the time, while everyone aspires to the modern, climatically unsuitable brick buildings.

Poorer quality homes built today vs vernacular self-build

Ironically we live in far poorer housing stock now than we did when we had the time to build for ourselves (stone/cob country cottage versus thin walled brick facade suburban house; earth dwelling versus high rise concrete flats), albeit with all mod cons (indoor WC, power showers, televisions, computers etc).

Over-complicated technologies

I noticed when reviewing my masters case studies that a lot of the issues were associated with technologies, emphasising the need for good passive design, minimising the need for add on technology.

Self-finish custom-build creates less waste

I also noticed that many of the user issues were to do with personal preference over fittings. One example I gave was at the Swindon case study by Habhousing (Kevin McCloud’s venture) with Glenn Howells architects and Stride Treglown landscaping. Small baths were fitted to save water use, however one father of 3 said he would have preferred a larger bath so that all 3 children can be bathed simultaneously and he will probably retrofit a new bath. Though this appears trivial, multiplied over a housing development it has waste implications. Had the occupants had final choice over these fittings, there would surely be less need for retrofit. In the self-build scheme in Stroud (Springhill Co-housing) by Architype, the community came up with a common design that was then subtly altered to individuals tastes in terms of fittings, room layouts etc.

This kind of semi-self-build seems to me to be a partial answer to the problem of self-build affordability, while still ensuring better quality homes with community and infrastructure. The biggest asset to the Swindon and Stroud schemes in my mind is the community and quality of design. These qualities would have been very high on the agenda of a vernacular builder, whether he was conscious of it or not.