Valuing a London balcony



New Member
Dear property experts, I need your advice! Please let me know if this is not the right forum.

We own a 2-bed (765 sqft) flat in Ealing, London (W5 zip code) on the 1st floor of an old Victorian house built in the 1890s. The flat has a 130sqft balcony. It so happens that the downstairs ground floor flat has been extended and on top of it there is another rectangular space of quite similar size to our existing balcony (I have attached a photo). We were thinking of potentially expanding our balcony, but from what we understand we need to negotiate a price with our downstairs neighbour to allow us to use the space as it belongs to him. Just to be clear, we were not thinking of building a room (he is definitely not keen) - just making our existing balcony into a bigger open space.

Trouble is, we have a no idea how to value an outdoor space. Do buyers generally value it per sqft, and if so how does outdoor space sqft price compare to indoor space? Is a balcony that is twice as big twice as valuable, or does the marginal value per sqft decrease? Or is it even more extreme and binary, in that buyers would generally pay extra for a balcony, but the amount paid would not change much beyond a certain size?

As one reference point, I looked at the valuation tool on and the marginal value of a balcony for our flat seems to be 20K. That must be based on some average estimate of balcony square footage, as the tool does not ask for the size of the existing balcony.

Any recommendations or reading resources would be much appreciated.

Many thanks!




Active Member
This as a very interesting topic because after doing a little bit of research I noticed that balconies may be classed by many peopleas a "green" elements with a potentially enhanced value?

I am not sure if is relevant but if you extended your balcony space to the left would this not impact light going into the windows below?