At this point, it should be highlighted that the structural design of a building in the real-world world normally require a qualified architect to underwrite. Therefore, it also needs to be highlighted that this section really has more to do with the ‘look & feel’ of the design rather than being a statement of its structural integrity. However, while the following designs are more about the use of living space, there is no obvious reason why they could not become the basis of a subsequent structural plan and initial cost model based on the cost estimates in the last discussion. So with the previous ‘health & safety’ disclaimers in mind, the following house designs will be outlined along with the rationale behind them:
Utilizes an awkward sloping plot of land, which might be acquired at a lower cost.
An extended family house, which might be shared by more than one generation.
Is based on an existing plot that might be re-developed in a cost-effective way.
A practical dream house, if money is no object.
In some respects, the first 3 designs are possible ways of addressing some of the problems raised in ‘The Reality of House Building’, which face any self-build project. However, as previously indicated, one of the biggest problems, in the UK, is the acquisition of a piece of land with planning permission. The likelihood of buying a piece of green-field farmland and then gaining planning permission for a house is so close to zero as to make no different to the average self-builder. However, the probability of finding a plot can be increased, if plots with awkward shapes and/or steep slopes are considered, which then require specific designs as discussed in House-1. Another approach is to look for plots with an existing house that might be re-developed as discussed in House-3.
So what cost model needs to be taken into consideration?
The selling price of the house designs outlined above will be initially based on a build cost of £1000/m2, such that it aligns to an ‘excellent’ quality specification, as previously defined, although this need not be the actual build cost to the self-builder. While the build costs are reflected in the selling price, there are a number of other key factors, e.g. location. Therefore, the selling price attached to each of the examples may be relatively arbitrary and only reflective of current house prices in my own local area. It might also be realised that new houses, constructed by commercial builders, will include some required profit margin. While the actual figure will depend on the state of the market, a figure of 15% will be used in the examples. Finally, there is one other major factor that needs to be taken into consideration, which is the cost of the plot on which the house is to be built. While the size and position of the plot will clearly be a major factor, the actual plot cost is also linked to the value of the house that can be built on the plot, such that we might quantify this cost as follows:
Plot Cost = Selling Price – ( Build Cost + Profit)
So, by way of an arbitrary example, let us assume that the build cost of a 4-bedroom 200m2 house is £200k, which is expected to realise a selling price of £400k and 15% profit margin of £60k. On this basis, the maximum plot cost from the perspective of a developer would be:
Plot Cost = 400,000 – (200,000+60,000) = 140,000
However, it is possible that the person selling the plot does not necessarily know the exact details of the house that the buyer is planning to build assuming the outline planning permission can be revised. As such, there may be some scope for a clever house design to exceed the assumed selling price on which the plot cost is calculated. There is also some scope for the ‘savvy’ and ‘capable’ self-builder to make an additional ‘profit’ through savings on the ‘build cost’. In terms of a self-build project, we might rationalise the potential profit as follows:
Profit = Selling Price – ( Build Cost + Plot Costs)
Now if a commercial builder can make 15% profit over above the build cost and plot cost, there is a suggestion that a self-builder might make 10% profit. This assumption is based on building a house of comparable quality and that the self-builder is capable of project managing the build to sub-contracted tradesmen. However, there is also some additional scope for our self-builder to reduce the build costs without necessarily affecting the perceived build quality by doing as much of the work himself and buying good quality, but possibly end-of-range stock via the Internet. If so, it might not be just wishful thinking that the build cost of £1000/m2 could be reduced to 800/m2 without any appreciable reduction in build quality. As such, we might revised the previous exa,ple calculation as follows:
Profit = Selling Price – ( Build Cost + Plot Costs )
Profit = 400,000 – ( 160,000 + 140,000 ) = 100,000
Here we see the potential profit, if the build costs can be reduced from £200k to £160k without affecting the selling price, which some anecdotal self-build stories may support. Of course, if it was that easy to make this sort of profit, then everybody would be doing it. This said, while designing a house to maximise a plot is not easy, it is not necessarily impossible and this will be the challenge taken up in the first 3 example.
Of course, sometimes it is just fun to forget about all the practical problems and just design a dream house in virtual reality, where large green-field plots with unrestricted planning permission go for next to nothing. This is why it is called a dream house.