Design Process
Single-storey house design
Many clients come to the first meeting at our studio and, even without yet being sure which plot the house will be built on, they already know whether they want a single-storey or a two-storey home.
Some even arrive with very clear layout plans, with room sizes and uses; others, however, come in with great enthusiasm but no idea of what their future home will be like.
While all options are valid and, of course, we always try above all to respect the needs of each client and each family throughout the design process, the reality is that the layout of a single-storey or two-storey house will depend on the plot available and the budget.
Even so, it is always worth assessing each option and the pros and cons of building on one or two storeys. In today’s post we will focus on single-storey house design, an option that is generally more economical and practical unless the plot does not allow it.
Let’s look at what single-storey house design involves, step by step:
Single-storey house design
1. Plot coverage
The first thing to assess is the total plot area. In many towns, the minimum plot size is usually around 400 or 500 m2 ; from there, a large plot is considered to be from 1,000 m2, and a very large one from 2,000 m2. Above 2,000 m2 we typically find rural plots. We can also find urban plots of less than 400 m2, but these are usually plots for terraced housing, whether single-family or multi-family.
If we are placing our home on a 400 or 500 m2 plot, we probably do not want to occupy more than 150 m2 on the ground floor, so that we have enough outdoor space, whether for parking or for garden or pool areas. In addition, regulations generally limit us and do not allow us to build more than 30% or 40% of the total plot area on the ground floor, which is known as plot coverage.
So, if we want to build a 300 m2 house on a small plot, we will have to build upwards and rule out a single-storey design, building at least two storeys.
As we can see, on conventionally sized plots, the decision to build a one- or two-storey house is very important in relation to plot coverage.
Coverage regulations
Single-storey house design can conflict with regulations if they are very restrictive or if we have few square metres on our plot. Coverage and buildability are two concepts to consider in house design.
Plot coverage is the total area, expressed as a percentage, that we can build on the ground floor, i.e., the m2 of floor area of our home.
Depending on each municipality’s regulations, coverage may include eaves, porches, or other elements that project from the façades.
For example, on a 1,000 m2 plot with 20% coverage, we can build a house with a maximum ground-floor footprint of 200 m2. This does not mean we cannot build two storeys of 200 m2 one on top of the other. To do so, we must check the regulations regarding buildability.
The buildability of a plot indicates how many total square metres can be built across one or more storeys.
Continuing the previous example, if we have a 1,000 m2 plot with a buildability of 0.3, we can build a maximum of 300 m2 of living space, adding up all storeys.
For this reason, it is important to check regulations before deciding on a single-storey or two-storey house design. In very restrictive cases, it will be worth considering building the home on more than one storey.
2. Adapting to the plot
Single-storey house design also involves adapting to the plot. Its slope and orientation will be decisive when planning the home.
Sloping plots and flat plots
When the plot has a steep slope, it will be more difficult and less advisable to build a single-storey house, as this would involve more earthworks and larger retaining walls, increasing construction costs.
In addition, we always recommend adapting to the plot as much as possible, since the connection with the outdoor space will be much more direct, and we will avoid major earthworks and large retaining walls, with the resulting visual impact.
In fact, many municipalities limit the height and total number of retaining walls precisely to avoid disproportionate walls that spoil the appearance of the natural landscape.
In general, if the slope is not too steep, there is no problem building a single-storey house, and some earthworks and soil retention can be carried out to create a sufficiently large, flat area to place the home.
On a flat plot, by contrast, single-storey house design is easier, and there is no need to work with different levels to adapt to the site.
Orientation, sun and ventilation
Orientation is something that, although it does not increase the budget, does affect our quality of life in the home.
In single-storey house design, it is necessary to plan which rooms we want to place on each orientation and what relationship they will have with one another.
Orientation is closely related to the slope, as it will determine the directions of views and privacy on the plot. Of course, the ideal case is a south-facing slope, where the views open towards the sun. In this case, it can also be effective to build a two-storey house adapted to the terrain, effectively doubling the south-facing façade.
However, having a slope that is not south-facing is not always a problem. Recently we carried out a project in Vallromanes where the slope faced west, so we adapted the house to the terrain to achieve the maximum south-facing façade.
In addition to orientation, ventilation is important. At our studio, all projects are designed so that, as far as possible, all rooms have cross ventilation. In this way, we renew the air quickly and effectively and, especially in summer, remove any heat that may build up indoors.
3. No stairs
Of course, the absence of stairs in single-storey house design is important for accessibility in the case of older people, or, for example, if we are in a cast.
But it is also important in terms of reducing the space we allocate to circulation.
Spanish building regulations – CTE – require the width of a staircase in a private home to be at least 1 metre. If we consider that a two-flight staircase takes up around 3 metres in length, this results in 6 square metres of our home being allocated solely to the staircase. On top of that, we must add the corridor circulation that will be created again on the second floor.
Therefore, in a two-storey house, the proportion of space dedicated to circulation will be much higher.
Is it advisable to design a single-storey house that will later be extended with a second storey?
In general, no. Although anything can be done, it is not advisable, as we would be building a roof in the first phase only to later demolish it and add a new storey. This is not very coherent.
Normally, if we want to plan a future extension of our home, it is recommended to extend it on the same level we already have.
4. Compactness
Compactness is a concept to consider in any project. The more compact a house is, the fewer metres of façade it will have and, therefore, the less energy exchange there will be with the outside.
In other words, a very compact house will be more efficient, as it will not lose as much energy in winter or heat up as much in summer.
In addition, this affects the total cost: one of the most expensive construction elements is the façade, as it involves multiple layers, including insulation and finishes that must be executed to a very high standard.
In relation to compactness, when assessing a single-storey or two-storey house design, we must bear in mind that building a 200 m² surface on a single level will make the home much less compact than if we build it over two storeys.
5. Possibility of incorporating courtyards
Although courtyards reduce compactness, in the Mediterranean climate they tend to work very well in many situations.
Single-storey house design makes it more feasible to incorporate courtyards and for them to receive more light, since the height of the surrounding walls will be lower. It is always worth assessing courtyards based on both orientation and the programme.
Courtyards allow us to improve ventilation, provide natural light, and add unexpected views in the design of a single-storey house, as well as multi-storey homes.
6. Roof accessibility
Logically, the fewer storeys our home has, the easier it will be to access the roof, whether for maintenance or to use it as a terrace.
In fact, when we design a single-storey house on a sloping plot, it is very easy to access the roof from the upper part of the slope, a circumstance many of our clients take advantage of to place a staircase and access the roof space.
Example of a single-storey house design
At Slow Studio, we offer a single-storey timber house design: a base model that can be adapted to the specific needs of each plot and each family.
It is a 110-square-metre home with 3 bedrooms, two bathrooms, a living–dining room and kitchen, plus a semi-outdoor porch that increases the usable area by 40 outdoor square metres during the summer months.
This is an example of a single-storey house design that works according to passive house principles, i.e., it minimises energy consumption through design strategies such as south-facing openings, cross ventilation, and high levels of insulation.
It is a model that aims to meet everything we have discussed so far:
– It adapts to the plot with small modifications, placing the porch to the south.
– It is a very compact square-shaped house of approximately 10 x 10 metres, which reduces energy losses across the façade surface.
– There are no stairs, and the proportion of corridors relative to the total is very low. In addition, the corridors are used to incorporate shelving for storage and a study or work table connected to the living area.
– In this case, there are no courtyards, as priority is given to compactness and to reducing the budget, but they could be included without any problem. In this specific case, the limited floor area of the home (110 m2) allows us to ventilate all rooms to the outside efficiently.
Single-storey house design will always be closely linked to the project’s development.
Each client and each plot are unique, so although in this article we have covered some general concepts, it is advisable to assess each case and consider all alternatives in relation to the client’s needs and, of course, the plot. At Slow Studio, the practice of which I am a partner, we meet with the client from day one through to completion of the build to achieve a home that responds to each situation.