Best way to convert a garage?

[garej]

Hi all. Thinking about converting my garage into a second lounge and am looking for experiences, either from someone who has done it or anyone with building experience.

The house is a relatively new build, built in 2017, garage is integral with a (very warm!) room on top, so we’re pretty sure it is properly insulated - at least the walls and ceiling. The floor is the bit we’re not sure about.

Both of the contractors we spoke to said it was very likely that it has been built the same way as the house but left at concrete slab level. However one suggested a wooden frame with insulation between the posts (sorry, English is not my first language so might be using the wrong terms), the other suggested laying a second concrete slab over the damp proof membrane.

Now, I know concrete is much more durable than wood but on a practical level, would it be better to do the concrete slab? Or is it something that would only make a difference in, say, 100 years’ time? What is swaying us to the wooden frame is mostly the time, the wooden frame contractor’s proposed timeframe is 3x quicker than the concrete slab one, but obviously we don’t want to have to do it twice, which is why I am asking for your help 🙂

Any insights, ideas, opinions, experiences welcome. Many thanks.

It can massively devalue a house
Some people will only buy a house with a garage
Are you able to take the loss (ie do you have a good loan to value/mortage free)

In a 2017 house - is it allowed? Are there planning restraints or covenants in place?

If you have got planning then detailed plans will include the building regs and address your questions about construction?

As above - check I'd you are allowed to do this. Some new estates put restrictions in place. Albeit for x number of years.

No plans to move in the next 20-30 years unless something drastic happens, of course. 25% LTV. We will have about 1/3 converted into storage space.

No restrictive covenants, several people have converted already. We have a 2 car drive as does everyone else on the estate, so very little on street parking happens. Planning says permitted development, building control says we only need a building notice so no need for detailed plans.

I’m guessing both would be allowed, I’m just worried about the longevity of the wood vs the concrete, I suppose. I don’t want to be a 70 year old dealing with having the flooring taken up to replaced the underfloor

We don’t build using wood much in my home country so I’m not very familiar with it as a building material.