Would a detached converted garage add value?

[Applepie21]

my house is valued at about 400k. There is an oversized detached garage at the end of the garden. I have been quoted 15k to convert half of the garage into a livable space and a toilet. The finished space will be 3.6m x 5m and is intended to be an office atm. The space will be properly insulated including floor, wall, ceiling.. My question is, do you think i can recoup this cost when I sell. We are looking to move but have no luck so far finding anything. Another question is, what is the reality with an outdoor office, Will walking through wet garden during the wet months be off putting? The garden is quite small, about 12m long, if it matters. All opinions appreciated, Thanks!

Just seen that OPs garden is quite small so they may not have as much garden stuff as we do to store which would make a difference, our garden is bigger and we have lots of gardening type stuff. I still think that you should only really do these things if you want them yourself not for the next owner unless it is maintenance related. It's like putting a new kitchen in to sell a house if it has a perfectly good one anyway, best to just point out potential when selling

If you are selling soon I wouldn't bother. Just get planning.

If you are staying then I definitely would. A separate space like that would appeal to all sorts of people - families with teenagers, man cave, outdoor bar - place to put up guests at a push.