Side Extension Plan

Its_not_paranoia

Doing something very similar in SW London, currently. 

That T shaped structural design is fraught with issues, and depending on the age and existing foundations will more likely than not require two sets of goalpost or picture frames as the structural design - not just the two beams resting on existing walls. 

On 'how much will this cost' the key question is 'what are you including'. Agree that the 70k thrown around already is a sensible ballpark for the headline of the builder's quote. On top of that you're providing the glazing (£6k?) Kitchen (1xk?), floor finishes, light fittings, bathroom furniture.......

There are architects fees, structural engineers, planning. I'd suggest you'll need to get you hands dirty and/or manage it very tightly to stay inside 100k. 

You need to get an architect involved, then a SE, then I would advise you to get a professional estimator to tell you the cost, to help you negotiate with builders (/come to terms with the price tag)

gab3x

Its_not_paranoia said:

Doing something very similar in SW London, currently. 

That T shaped structural design is fraught with issues, and depending on the age and existing foundations will more likely than not require two sets of goalpost or picture frames as the structural design - not just the two beams resting on existing walls. 

On 'how much will this cost' the key question is 'what are you including'. Agree that the 70k thrown around already is a sensible ballpark for the headline of the builder's quote. On top of that you're providing the glazing (£6k?) Kitchen (1xk?), floor finishes, light fittings, bathroom furniture.......

There are architects fees, structural engineers, planning. I'd suggest you'll need to get you hands dirty and/or manage it very tightly to stay inside 100k. 

You need to get an architect involved, then a SE, then I would advise you to get a professional estimator to tell you the cost, to help you negotiate with builders (/come to terms with the price tag)

The house is 1900 (+/- 10 years).

I was hoping we are looking at £70k all incl. max. I was reading on Which to budget £28k for 12m2 extension + 10% architect fees + 10% structural engineer. Kitchen £10k, bathroom £7k, electricity + water £7k, convert large bathroom upstairs to room and lavatory £7k then leave 10% of that total for contingency ~ £70k. Adding those 12m2 would in effect cost £540/sq ft.

I have to be conservative and take £600/sq ft as realistic sale price so anything above £70k total would carry a high risk of not recouping the cost.

If that is unrealistic then I might just have to contend with as is which is also very good, and I'll have to find myself another project.

Its_not_paranoia

I've found the cost/msq estimates to be an absolute joke, partly because mine is pretty small, and mostly because of the structural design. 

Losing the side return wall my structural engineer required a picture frame in the middle to keep lateral stability in the house. Other houses on my street have the same too. 

On the plus side I have an existing party wall, which is a nice saving. 

Building quotes to plasterwork were 30-50k plus vat, with the estimator saying that 35 is about right. Then there's the decorating, kitchen fitting, and supply of kitchen, glazing, floor finishes, which means I might squeeze mine out for 70k all in if I do all decorating, joinery, tiling, floor fitting etc. I'm also doing nearly all the electrical work myself. 

Given that yours is a lot bigger, two storey and doesn't have the new external wall already in place I'm suggesting you might get it for 80 or 90 (now including vat, glazing, kitchen etc) if you did a lot yourself (e.g. decorating, floor fitting etc) or realistically need a starting budget of 100k. 

gab3x

Its_not_paranoia said:

I've found the cost/msq estimates to be an absolute joke, partly because mine is pretty small, and mostly because of the structural design. 

Losing the side return wall my structural engineer required a picture frame in the middle to keep lateral stability in the house. Other houses on my street have the same too. 

On the plus side I have an existing party wall, which is a nice saving. 

Building quotes to plasterwork were 30-50k plus vat, with the estimator saying that 35 is about right. Then there's the decorating, kitchen fitting, and supply of kitchen, glazing, floor finishes, which means I might squeeze mine out for 70k all in if I do all decorating, joinery, tiling, floor fitting etc. I'm also doing nearly all the electrical work myself. 

Given that yours is a lot bigger, two storey and doesn't have the new external wall already in place I'm suggesting you might get it for 80 or 90 (now including vat, glazing, kitchen etc) if you did a lot yourself (e.g. decorating, floor fitting etc) or realistically need a starting budget of 100k. 

This is absolutely amazing and thanks for the additional context. I have no skills to do anything other than paint so this means I would be looking at the £100k mark. Really not sure if this is worth it.

By the way, mine would be a single story extension. Upstairs, I would make my bathroom into a bedroom and a small toilet. Nothing structural upstairs.

Lots to think about.. thanks!

casper_gutman

I think the plans look great, but I'd echo what others have said about costs. The "£x per square metre" figures you find on the internet might give a guide for building a relatively large  box of an extension in a clear space, but your project consists mostly of intricate structural modifications to an existing building and much of the cost will be in the remodelling not the new part.

Your steelwork is not just a straightforward beam, and an existing house from 1900-ish will be built with shallow brick footings or similar so will need new foundations to support where the steel lands. By the time you've had a new kitchen and bathroom fitted, floors, rooflights etc. I really don't think this is something where you'll have change leftover from £100,000.

Its_not_paranoia

PS. My builder works primarily down your way, and if he gets mine finished off nicely in the next few weeks I'll be happy to recommend. 

If you do press on with your project, I think you need architects plans and structural engineers design to be able to have a sensible conversation with builders. (i.e. to have spend perhaps 2k on fees)

The way I look at it, is that I get to live in exactly the house I want, so the requirement isn't to make profit on the sale. Living in the house is the profit, and if it almost pays back on sale, then that's a win. 

GDB2222

I have absolutely no problem with a bathroom without windows. Most hotel bathrooms are like that, and they are fine. 

However, a downstairs bathroom is not for me! 

thegreenone

As you seem to have a good idea of what you want, perhaps find an SE to do the plans/SE element. You don't have to have an architect. My husband is an SE and has done start to finish plans/applications for family and close friends.  (One more year until retirement otherwise he might have been able to help).

Have a chat to the planning/BRegs department to see if there is anything else that needs to be taken into consideration. 

Once you have proper plans* drawn up, you can approach builders for estimates.

*No offence, yours are a very good starting point.

Rosa_Damascena

GDB2222 said:

I have absolutely no problem with a bathroom without windows. Most hotel bathrooms are like that, and they are fine. 

However, a downstairs bathroom is not for me! 

I quite like a shower room downstairs, just not as the main bathroom!