Do I need a Feasibility Study?

It sounds grand, doesn't it? A feasibility study? Something more appropriate to commercial developments than for home owners? Let's explore what it is and how it might apply to your project though.

The Cambridge English Dictionary defines 'feasibility' as

"the possibility that something can be made, done, or achieved, or is reasonable"

and for once, the professional meaning in a construction project is the same.

Can it be done?

Next question,

Can what be done?

Can we build a new house at the end of our garden?

Studio Hobohm completed a detailed Feasibility Study for clients who were exploring the possibility of building a new dwelling in their large garden.

So the first question was,

"Can we build a detached house in our garden?"

Perfect, but hang-on, what kind of house?

Well I don't know, that's why you are doing a feasibility study.

Ok, but what do you want this house for?

And now we are touching on the Brief - which I talk about in another post. This isn't about how you want something to look (although if you have strong ideas, by all means, tell me now) this is about why. It might be as an investment, or to get a bigger, or a smaller house than the current one. It may be because you have individual needs like accessibility, a particular hobby that needs a certain kind of space or maybe its something you've always wanted to do. Something is driving your initial enquiry to an architect or designer - what is it?

Whatever it is, it will form the basis of the feasibility study.

Our headings were:

• Site

• Context

• Planning Constraints

• Space Planning

• Volume / Scale

• Green Technologies / Energy saving

• Utilities

• conclusion

The information under each of these headings will overlap but it can be helpful to break it down so that you can see how I, or another architect/designer, arrives at their recommendation.

The site tells us the available area, the orientation and sun path. It might also flag up a large tree, a deep sewer or changes in level. All these start to inform the potential size of the development. Then we consider the wider context: neighbours, usage patterns (shops, schools, housing) and this will feed into the consideration of planning constraints.

These headings apply as equally to a house extension as they do to a new building.

For space planning I looked at a 2011 report by the RIBA called "The Case for Space". At the time there were many discussions in the government and construction industry about national space standards but nothing was in place. Today the government issues Statutory Guidance in the form of "Technical Housing Standards" which sets out minimum provisions for different size dwellings. These are not adopted by all Local Authority and London has its own requirements so specific requirements will come up as part of the planning constraints. For my purposes they formed a useful check on the sizes and types of accommodation we could theoretically fit on the site. I worked out a basic area and a variety of footprints and then moved onto Volume and Scale.

It became clear as I analysed the parameters that it would be difficult to achieve all the desired spaces on the ground floor. A first floor or attic room would allow for a more efficient volume - but would it 'fit' the context and would the planners agree?

The final 2 headings, Green Technologies and Utilities were particular to this project at the time but in fact are key to every development, no mater how small, today.

By Utilites I mean water, electricity, gas and drainage. One key aspect which I confess I failed to highlight as a potential issue at feasibility stage, was surface water drainage. I learned the hard way - we have a huge area of water attenuating crates on this site and it was an unforeseen cost due to a planning condition. Dealing with surface water and flooding is of ever more importance so I don't take the requirements lightly and our cities' drainage infrastructure is generally overlooked and undermaintained. You may not want to go as far as a ground condition survey or drainage searches and surveys for your feasibility study but don't forget it all together.

My final heading was 'green technology' but these days I might separate this into 'energy conservation' and 'technology systems'. These requirements are sparked by your brief and also your architect's recommendations. Arguably all energy conservation strategies are desirable but the feasibility study can highlight the implications of each. For example, on this project, it was decided that the space requirement for an MVHR (A mechanical Ventilation Heat Recovery) system made it unfeasible. As far as technology goes, houses have the potential for a multitude of integrated operating systems: security cameras, sound systems, heating controls, lighting, not to mention internet access, even remotely checking your fridge. If this is part of your aspiration then flag it early so the full implications to the design, budget and build are understood.

Maybe you are still thinking this doesn't apply to your kitchen extension or garage conversion, but believe me, it will be the basis to those first concept sketches your designer puts in front of you - or should be.

My conversations with the hopeful owners of the large garden revealed a passion for bamboo plants and many things oriental. It drew me to the motif of a lacquered puzzle box and a mood board of materials and these, in turn, brought us quite quickly to a successful concept for the house itself.

From my point of view the feasibility study was invaluable and formed the basis of the pre-application planning submission, clearly illustrating to the planners the careful consideration being given to the development.

The resulting planning permission was approved without being called to committee and the construction detailing was able to proceed with the security of a solid investigation behind it.