Why would you want to read this? Because, in the drive for having space around your house (because you want to work from home, so you want more space and to be 'in the country') you probably cannot have both a newer house and 'more' space. The reason for that is to do with planning regulation and house-builders' profit expectations.
We measure housing density in residential units per area unit, such as u/ha. When we exceed 30u/ha it is difficult to meet sustainability objectives such as urban cooling and biodiversity. [10] Looking specifically at Blackpool [11], which is only 14 square miles, we have a target of 300 dwellings per annum at the moment. For the period 2012-20 there were 250 houses on greenfield sites and 1750 on brownfield (previously developed land, PDL). I see that ratio 1:7 as being pretty good. [11 pp10-13 have relevant tables]. What I'm interested in is density, which is something each local planning authority is supposed to set for itself, reflecting local circumstances. Simultaneously the authorities are expected to go for 'optimum density'; I do not see this as measurable at all, but one could presume that greater accessibility allows for increased density. I guess means identified spare capacity in infrastructure such as roads, drains, utility supplies and services such as education and health. Apparently it means being within walking distance of some sort of local 'centre' or with particularly good local transport. Again, I do not see how this can be sensibly quantified and I am sure it should be, rather like an EPC for a house. The densities are classed and below 30 u/ha, between 30 and 50 and above 50. For Blackpool, 2019/20, that was 38%, 38% and 24%. A google search shows that in Essex, for example, detached and semi-detached go=housing would be at a density below 20 u/ha, which is an eighth of an acre each.
I then wonder what density applies in my immediate area. One could work out one's own density; one unit on say 0.2 hectares is 5u/ha, but you should include your road and pavement frontage and your share of any adjacent green space. 30u/ha spread evenly is 0.033ha each, 330 square metres or a plot 15x22 or 11x30, which is about what we have.
Fifty units per hectare means 200 sq metres each, say a plot of 10x20m less your share of the road (3.5 to 5 metres) suggesting a single residence plot might be 10x15 or 8x20 (metres). So a small house at 70m² with a 8m plot width might have a footprint of about 8x4.5, leaving total garden length of about 15 metres. if you expect to park your car on your own land then the front is 4m or so and so the back garden, once you've allowed for footings and drainage pipework, is going to be 7x10m. if the plot width is 10metres, the back garden switches to more like 7x5m. In practice, densities as high as 50u/ha call for other green space within the development. In and close to city centres one expects densities exceeding 100u/ha which means flats and apartments, high rise and heavily shared green space. Houses of multiple occupation (HMOs, Blackpool has very many) have their very own issues, not least those of parking and waste collection. An HMO is defined as a property that is let to 3 or more people from 2 or more households. So one (or more) is not related to the others. So a couple renting a room to a lodger is an HMO and will need a licence – and quite probably that entails all sorts of additional building work to meet the required standards. I note in passing the use of the grocer's apostrophe in (incorrectly) offering HMO's as a plural. I attempted to count the number of licensed houses in Blackpool; it's about 1400, 900 of which lie in my immediate area; 31 are in my street. These are not all HMOs and there are quite a lot of houses that are licensed and classed as 'house in single occupation', which I think means that there is a waiver of sorts on council tax, either 25% off or minimum band. For my street that removes 12 of the 31; there are 200 houses, so we're looking at about 10% of the houses as being HMOs, having flats or other forms of multiple occupation.