"Le programme": minimum buildable area

Hello @reef-building,

At the last plenary meeting we had a brief discussion about the fact that the architects sometimes indicate that the site is a bit too small for our programme.

This created some confusion, so I put some numbers in an Excel to see what would be the lowest we could go in terms of buildable square meters. It is saved in Team Building > Scouting exercise > Buildable area estimation (internal link).

The essence is this:

  • The architects work with a benchmark of 3294 m² buildable, which would be 25 units of 90 m² net.
  • If we go for 25 units of 80 m² net, the number goes down to 2928 m².
  • If we go for 20 units of 80 m² net (lower end of the Blueprint), the number goes down to 2342 m².
  • If we go for 18 units of 80 m² (Blueprint with a 10% error margin), the number goes down to 2108 m².

(patting myself on the back for my successful numerical juggling :muscle:)

So when they say “it does not fit your programme”, these are the numbers we can use to put this into perspective.

These numbers say nothing about the financial implications, which is something that is done in each and every feasibility study. The bottomline (as explained by Alberto below) is this: the lower the number of square meters and the lower the number of floors, the higher the number of fixed costs we have to divide among us, hence the higher the price per square meter. That doesn’t mean we should discard these sites rightaway though. We can do a first estimate ourselves, but normally the feasibility study should unveil, well, if a site is feasible for us.

I’m moving two (earlier) posts from the Team Building thread here, because I believe this is something we need to be able to find back without too much trouble.


@alberto (or any other number cruncher with a calling :slight_smile: ) can you please have a look at the simulation that I made, and see whether it is correct?

It is saved in Team Building > Scouting exercise > Buildable area estimation (internal link). I also left a copy of the architects’ estimation in that folder, so that whoever wants to can play around with it without risking much.

If it is correct, then as a next step let’s create a separate post about this, and after that check in with the architects.

To be clear: this is only about the surfaces and does not include implications on costs (even though that could be built in if needed).

I saw it. What do you imagine using it for? I could imagine using it to extend the range of candidate sites. If we build only 18 units with an average size of 80 m2, we only need to build 2,108 m2 (instead of 3,294), so we can afford a slightly smaller plot. This could potentially unlock some extra candidate sites (though then the garden might become smaller than 900 m2).

However, this is certain to have implications on the price per square meter.

To explain this, I first need to make clear what square meter we are talking about. In this estimation, the architects have a new (for me) concept: the vendable square meter. This means a private, gross square meter. Each vendable square meter comes with a pro quota part of the common spaces and the utilities (corridors etc.), that are not sold alone, but only in bundle with the private units. Our estimation comes to 2,700 m2 vendables, but that requires building another 594 m2, and that’s not even counting the underground parts. The estimated price means that, if we sell 2,700 m2 at that price, we can pay for the whole thing: the 2,700, plus the 594, plus the underground part.

Also note that, whereas the commons were made to be 10% of the private space in the very first estimation, now they are 594/2,700 = 22%.

With that out of the way, the estimation imagines spending 1.5 mil EUR for the site. With a going rate of 1,000 EUR per m2, that means a 1,500 m2 site. The two that we sent to the architects yesterday are, if memory serves, 3,000 m2 and 2,700 m2. Even if we were able to build The Reef to the specification in that estimate, out total bill would go up by at least 1.2 mil. I have calculated that every extra 500K EUR paid for the site adds 185 EUR to each m2 vendable. So, if you are buying a 100 m2 apartment, a site that costs 2 mil instead of 1.5 will translate in you paying an extra 18,500 EUR; a site that costs 2.5 will translate in an extra 37,000, and so on.

With fewer, smaller units this effect is componded further: the cost of the site is now spread on a smaller number of vendable m2. Where fewer and smaller units might give un an advantage is if they allow us to buy a smaller plot (for example a 1,200 m2 one), because this will result in more plots available on the marker, and in a smaller cost of the site per m2.

In general, I am looking forward to the feasibility studies, because they might suggest we need to add another criterion: we need to build four stories or more to be economically viable. Low-lying cohousings like Spiegel are pretty, but expensive in terms of the incidence of the cost of the site per vendable m2.


Thanks for the comprehensive info @alberto! I think that we’re all hoping that these first few feasibility studies will provide us with a clearer idea about what we should be aiming for :slight_smile:

Exactly that. If we can avoid discarding sites because they are supposedly too small, that would be a great win.

I’ve never heard this phrase before… does it apply to everything in the Blueprint (garden, distance to train station, etc.)?

Thanks for this to both of you, much clearer now…

Can you explain what the extra 694m2 are? I get the feeling that it is common spaces +corridors, in which case I think it should be 594m2, no? But it doesn’t change much to what you said though…

1 Like

Right on both accounts. I do mean 594: changed now, commons + corridor m2 comes to 594/2700 = 22% of the private m2. Values in EUR are computed on the basis of the 2,700, so they are unchanged.

1 Like

We have never discussed this, and I propose that we do take this up once we make it through the reviews that are planned, but for now I can indeed well imagine that a 10% error margin will overall be a reasonable proposal. If for example an otherwise excellent site is 33 minutes away from one of the main stations, I would find it odd if we would reject it right away.


Same file as the post above, now calculating the absolute minimum, the ideal average and the absolute maximum number of square meters:


Internal link | Publicly accessible link