Experience with changing upstairs layout or adding an upstairs extension

[TheBirdintheCave]

At some point in 2026 we'll have the funds to buy and renovate a larger home. We've found a house we love, it's in the road behind my brother's house is within budget and the downstairs floorplan works well as it is. Upstairs is less favourable. The master bedroom lacks an ensuite and the bedrooms that would become our kids rooms are smaller than their current (shared) bedroom.

I've drawn up some basic plans on PowerPoint of what I might do to correct the issue. After expenses to replace the 70s kitchen and convert the garage into a playroom/guestroom, we'll have about £70k left for any further remodelling. The area is a big mixture of differently priced houses and we're looking to make a forever home so I'm not worried about resale price.

I'd love to know if anyone here has had this sort of work done before and what it cost you. Would a £70k budget actually cover any of this or am I dreaming? 😅

Options:

A: Change the walls to create a new master with ensuite, two more evenly sized (though still small) kids bedrooms and a small study.

B: Add an extension over the garage to create a master bedroom with an ensuite and knock through two of the bedrooms to make three large bedrooms in total and one smaller guest room/study.

C: Stop trying to force the house to fit our needs and hope something else comes up that's more suitable.

I feel like C is the most sensible option unfortunately but my heart isn't ready to let it go just yet! 😂

£70k would easily move the walls if they are plasterboard. If they are structural that will cost more, particularly if you need steels to support the roof. I think it’s tight to go over the garage, also its foundations may not support another storey. Also depends where in the country you are.

We built a new upstairs bedroom but needed to demolish the old garage and single-storey rear extension to make a bigger footprint and add steels (the garage and old extension couldn't support the weight of the new room).

We're in Sussex with a fast connection to London so unfortunately are paying London commuter belt prices for everything x_x

Good to know that moving the walls might be a possibility at least :)

Interesting that you've both mentioned foundations, I didn't even consider that.

How would one find out something like that? Is is something that would be on a survey or mentioned in any of the houses documentation that an estate agent would have? Or would it literally be a gamble that I could only know after buying the house?

I would get a builder round. They may well have some ideas you hadn't considered about making the layout work for you. Regarding foundations, I'm no builder but I would assume any single storey garage or extension would not cope with the weight of another storey.

You need to dig a hole to find the foundation depth

A Steel frame can be used on pad foundations if the garage can’t take the additional weight of another floor altjough the average builder usually prefers a strip foundation so may need to knock it down

A structural surveyor can advise on this and whether the existing garage is sufficient as is. Probably not though as they are usually single skin with intermittent brick pillars to take the roof

Estate agents won’t have this info. If it’s a relatively new property the plans may still be on the planning portal online with the local council

If you go into the roof you can see how the roof is supported and on which walls below to give you an initial idea of which ones you can remove
Again check with a structural engineer before anything is removed

The option with new windows: May be very hard to get planning approval if that is the front of the house.

Option D: move the walls to create 3 bedrooms plus en suite and ditch the study?

It’s only an issue in a conservation area or on a listed building.

If not then it’s just a planning application

I think Option A (moving the walls) is definitely do-able. And the sizes of the rooms look fine to me.

It’s all very well waiting for something bigger but if you love the area it is a bit of a risk- what if the bigger property never comes on the market? And could you afford it if it did?

The other thing to consider is whether you could go into the loft?

Unfortunately I work from home so need some form of office space which is why we needed a four bedroom house. Otherwise that would work great.

Yeah I spent about an hour last night looking into this as I’d totally forgotten it was even an option.

Downside is it’s a 70s build and I’ve read that they’re trickier to convert as the roofs are lower.

Could be a viable option D though!

No way, plan C sucks!! You seem to like the house and the downstairs and the location and building something to your spec is fun. And you have the money. I vote over garage and whack a garden office in.

(we did 2 bedrooms over garage - but we converted garage into kitchen - and have had a garden office for about 3 or 4 years now, used every day)

I think 70 might not be enough to build out over the garage even assuming the foundations were ok for that - roof work etc adds a lot to the cost

many Houses built in the NE in the 70s could take a over garage extension with no problems -if lots have been done then I would think it would be ok

moving the walls is small rooms for the kids - have you tried fitting the furniture into your plan?

Option C

Yes! I had lots of fun with this on PowerPoint based on the dimensions of our existing furniture 😬 It does all fit but yes, I don’t like that the rooms are small. One of the reasons we’d be leaving where we are now is to gain space and I definitely want the children to have more of it. Although they do share a room currently so I suppose even having their own space is technically more space.

Can I chuck in that I dislike en suites. Our builders pushed for us to have one and we chose to position the door to have a communal shower with toilet plus separate bathroom. Such a better set -up for us, as a family of 4.

I’m too used to ours to not have one in the future now I think 😅

I did an extension over my garage recently, knocked through downstairs to give a large kitchen / diner and now no garage! There was quite a lot of work, as i also remodelled downstairs to get a downstairs office. My garage had sufficient foundations for the extension - confirmed by a structural engineer after house purchase - but I had to build walls inside in order to meet regs, particularly insulation requirements. It cost more than £70k but less than £100. I'm in the Midlands. I'm not worried about future sale price, as we intend to be here at least 15 years.

Should have said, the upstairs extension was a bedroom and en-suite.

Could you not use bedroom 4 as an en-suite to bedroom 1 - you'd have to check out costs of putting in sewage/water as it's not near the existing bathroom and then putting home office in the garden?

I thought that would be way more complicated than just putting an ensuite next to the current bathroom. Plus then we’d still have to somehow make the other two bedrooms bigger :/

Totally agree with this. Much more flexible!

you can do a loft conversion for your office - if it’s not going to be slept in it doesn’t need the same construction requirements so can be much cheaper to achieve than if you’re adding a bedroom. For less ££ you could have a fabulous big office with amazing views and restructure the walls below to have 3 big bedrooms - quicker and less disruption too.