Extension- where to start?

[Dilbertian]

We want to replace the kitchen, build an extension for a utility room and move the boiler into it, and remodel the patio.

How do I go about this? All I know is that I like the kitchen in Friday Night Dinner. Where to start?

Draw it out

Yes plan what you want first. Then research to get a ball park likely cost to see if you can afford it.

After that drawings. Then quites from contractors. Planning /building regs if required.

If you know what layout you want, and don't think you need an architect, then get a structural engineer to do the specs for your builder. These will be used for building regs too.
You could also research all in one firms that will design and construct, but you will obviously pay for this extra level of involvement. Houzz is a good place to research the people you need on your area.

Start by thinking about the space you want to create. How many square metres will that be? As a very rough estimate, work on the assumption of £2k per square metre, plus VAT for the plastered shell with windows, electrics, plumbing. Then its a question of trawling through various websites to get an idea of what you want & prices - kitchen / utility / flooring / light fixtures / upgrades from standard builder's fittings (e.g. if you want nicer radiators or plug sockets / light switches), and bank on maybe £700-1500 for moving the boiler maybe? Velux windows?

Once you've got a ball park figure, you can see whether you can afford it / think about how you're going to finance it.

If that all stacks up, then its a question of getting some drawings prepared, seeing if you can do it within permitted development or whether you will need planning permission, and then getting some quotes from builders.

Thanks, this is exactly the sort of info I need.

How do I know whether I need an architect or a structural engineer to do the drawings? I have a fairly good idea of what I want, but don't know whether it's possible out how best to achieve it.

In the rough sketch, blue is the existing house and red is what I want to extend. The house is already extended, so I don't know whether further extension would fit within permitted development. That's one reason why the patio remodel would probably be roof and floor only, rather than a fully-walled sunroom.

It depends - I would do a ring around of local architects / structural engineers (if you look on your local planning portal you can see neighbouring properties that have submitted drawings and they will have the name of the company that has done the drawings listed on them ) and just ask whether they'd give you some advice / idea of cost.