As part of our series on planning issues and rules we move onto a topic that causes much head-scratching. This is my interpretation of how to work out:
Surfaces Hors Oeuvre Brute (S.H.O.B.)
Surfaces Hors Oeuvre Nette (S.H.O.N.)
click on image to enlarge
Surfaces Hors Oeuvres Brute (SHOB)
This is the starting point from which the SHON is calculated by subtracting certain areas that are allowed. These will be explained later. The SHOB of a construction is the total floor area of each floor of the building. It is easier to think of this as the buildings footprint. It includes roof terraces, balconies. loggia and lean to for example. It also includes the thickness of external and internal walls. Porches, awnings that rest on posts must be included to the outer limits of the posts. Staircases at ground floor level are also counted.
Surfaces Hors Oeuvres Nette (SHON)
This measurement is determined by subtracting from the overall SHOB measurement areas that technically cannot be lived in; Garages used for parking vehicles (motorised or not), Balconies, Covered exterior walkways and areas, in eaves for example, below 1,80 metres in height. An allowance of 5% is then made for wall insulation (multiply total by 95%). Two further reductions of 5m² can then be made for sanitary improvements and special needs, handicapped persons provision.
If this figure is below 170m² an architect is not required to prepare plans for Demande for Permis Construire submission.
Many thanks Steve, a useful site. Can I just clarify on SHON that you divide the initial result by 95% for insulation (i.e. make the answer bigger) rather than multiply by 95% to make it 5% smaller.
Regards
hi Gerry.Thanks for the mail What you want to do is reduce the total by 5% so you are correct multiply
before you subtract the two extra allowances, The mistake on the graphic has been corrected
Thanks Steve, a very useful and handy site…
at the moment I am trying to calculate the SHON of a house we are designing- to be built in rural france. as far as i can see, the walls (internal and external) are included in the calculation? we are building with straw-bales so the wall space adds a large amount of area to our calculations!
In the upper floor of our design a portion of the space on the edges is less than 1800 in height. does this mean we would not include any external wall thickness in our calculations, as well as subtract the area under 1800h? there seems to be a few contradictory examples out there.
Also, do we include bathrooms and wcs in the calcs?
thanks, murray
Hi Murray,
Many thanks for the kind words re site, glad you are finding it useful.
If you click on the two diagrams they will enlarge to a reasonable size that allows you to see graphically how to work out the figures. The wall thickness is included as it’s part of the building footprint. Remember to multiply by 95% and then subtract the 5m2 for the bathroom, “sanitation” allowance. Straw bales, would be interested in seeing some pictures and words as to why you went that route as, I suspect, would other people reading the site. Best wishes for the planning and construction.
All the best
Steve D