How to estimate the size and price of your appartments

Hello @reeflings,

Below is an explanation of the different steps to follow for calculating an estimation of the size and price of you future dream appartment :slight_smile:

This is a necessary step before seeing the banks and the confesseur, and will also be information needed for the Programme (the survey that will help us assess our surface needs to pass on to the architects).

Because the estimate has changed substantially recently, @reef-full is kindly invited to have a look at this as well, and check whether their wishes still matches the new budget, or if they need to adapt the size of their apartment (if you haven’t done so already).

You can use the size and price calculator (see link below) for all of the calculations below, but do read the information in this post which have additional details.

A. Calculate the size of your appartement

1. Calculate the net size of your appartment

For the estimation of the price of your appartment, you will first need to decide what size appartment you want.

To start with, the easiest option is to calculate a “net surface” or “carpet surface”; this is the surface of your appartment excluding the inner and outter walls, also known as “carpet surface” (as in the surface of carpetting you would need to cover the ground of your appartment).

Below are a few tips on how to estimate this.

Refer to the overall minimal and standard appartment size

Below are some standard net surfaces for an appartement, based on what the architects said was doable for them (so don"t expect to be able to go lower)

  • 35m2 for a studio
  • 55m2 for a 1 bed room appartment
  • 75-78m2 for a 2 bedrooms appartment
  • 90m2 for a 3 bedrooms appartment (but that is quite small; might be doable in a new building (definetly not if renovating))
  • Well over 110m2 for a 4 bedrooms appartment (exact number to be confirmed)

Use the calculator

If you want extras or if you want to be creative, use column C (standard surface) of the size and price calculator (internal link) to get an indication of how much it would add to the minimum. You can play with the file by changing the info/numbers in the blue cells (please download this on your computer to do so!)
Use the corresponding tab at the bottom of the table, depending on whether you want an appartment or a studio.

Check the small unit post

If you are interested into a studio or 1 person flat, you will find a post on small units on Edgeryders.

Get a feel

You can always have a look on an immo website (e.g. Immoweb or Immovlan) to get a feel of how many square meters feel good to you. A more accurate option is also asking to have a look at the apartments of other Reeflings who have measured their appartments, eg. Lee (see this document ).

Err towards the lower estimate

When in doubt, don’t hesitate to take the lower estimate of what you think you’d like, for the following reasons: 1) You’ll have plenty of common spaces that you can use (e.g. guest room, dining corner etc.), and 2) Our architects are masters at making a good use of small spaces

2. Calculate the “gross” square meters

Multiply the number of net square meters by 1.25. This is because everybody needs to pay for the outer walls and insulation around their apartment, and account for the inner walls which will add to the surface of the appartment.
This is the so-called “gross number of square meters” (“surface brute” in french), which will be the reference that will be referred to when talking with the architects, the notary, etc…

As a point of reference, here are the architects’ recommendation for standard appartment size (see A1 above) converted into gross square meters:

  • 44m2 for a studio
  • 69m2 for a 1 bed room appartment
  • 94-98m2 for a 2 bedrooms appartment
  • 113m2 for a 3 bedrooms appartment (but that is quite small; might be doable in a new building (definetly not if renovating))
  • Well over 138m2 for a 4 bedrooms appartment (exact number to be confirmed)

B.Calculate the price of your appartment

1. Calculate the cost of the apartment

Multiply the gross square meters with any number between 3750 and 4600. Take a number of the lower end of the price fork if you are happy for your unit to be located anywhere in the building, take a number on the upper end of the price fork if you’d like to be on the upper floors or if you want other features that increase the resale value of the unit.

In the calculator, you will find a minimum and maximum overall price, based respectively on the lowest estimate of 3750 euros/m2 and the highest estimate of 4600 euros/m2

2. Add extras

  • Terrace (1500euros/m2). Note that it may become compulsory to add a terrace space that equals 10% of the net surface of the unit, with a minimum of 5 m² (e.g. 7 m² of terrace for a unit of 70 m² net).
  • Cave (1350 euros/m2)
  • Garage (30 000 euros). Note that a parking spot will not be mandatory, and that we’ll find a solution to share the burden of the total number of mandatory parking spots.

3. Add a 15% safety buffer

For this, multiply the price of the apartment by 1.15.

Normally we would have worked with a 10% safety buffer to provide for unexpected factors that increase the cost of the project, yet because of the current economic and geopolitical situation, unfortunately we need to take a 15% buffer.

Vice versa, what this means is that if you get the green light from the bank for a budget of x, you need to divide that sum by 1,15 to obtain the maximum budget for your unit. Should there be an unexpected cost, you then don’t need to worry that you won’t be able to borrow the extra money needed.


@reeflings: it would be good if a lot of us did this, because it is the most helpful thing to know what you want. If you do this, could you also let us know more specifically what surface of corridors you have for a one bed room, 2 bedrooms, etc…? Thanks!

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Can we not ask everybody to fill it in? So we can base Le programme on it ?

We could, but I feel we may go through a google survey to have all the data together at once?
And we could always ask them later. Let’s first talk about our plan in a meeting, and then see what we need to do…

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Well if every new member use this file for going to confesseurs, why would we ask them to fill in the google survay too ?

Maybe you can start a simple Word document somewhere on Nextcloud? I have my measurements, so under my name I would just put some bullet points with the lenght, width and total surface of the different spaces. Doing it like this would have the advantage that it’s free format, and everybody can share what they feel comfortable sharing?

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I think we need to separate the two processes anyway, so we’ll do another post when we are ready to do Le programme. Also there might be additional info we might wanna ask…
We don’t have to do a survey if we think it’s not needed, we could also use this file, let’s discuss it!


Finally getting this one off my to do list.

I created a document where people can add the measurements of their apartments, and I included those of mine.

This is the link:

@Sarah, can you maybe add this to your wiki above?

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@reeflings I’m really sorry but I didn’t save an important edit for this post, namely that you should primarily refer to the standards shared by the architects, and use the calculator only if you want something bigger…
You should take this into consideration before doing le programme 2.
Again, sorry about the f*** up!!