Adding second storey to single storey side extension

[JayBo1979]

Hi there,

We have a single storey side extension that currently houses our kitchen. We are thinking of adding a second storey on top of it and also taking it further out towards the front of the house, keeping two of the existing walls, assuming the footings are good enough. I found a building control document that says the footings for the extension are 600mm wide, 250mm thick and 1 metre deep concrete. (see attachment). I assume this should be sufficient for a second floor?. (I realise we will have to get a structural engineer to check them over properly)

Assuming the footings are good enough does it make (economical) sense to keep two of the existing walls (back and side and maybe part of the front), save the kitchen and just take the existing extension further forwards- rather than knocking the whole thing down and starting again? One builder said its possible/feasible, while another said we should knock the whole thing down and start again (and quoted a much higher price)

If adding to an existing extension, the second builder also said we would need to update the insulation etc for the old extension walls to meet current building regs. The first builder never mentioned this- can anyone clarify?

Another thing they differed on was saving the kitchen. The first builder said the ceiling joists in the kitchen were good to build on top of and that we wouldn't need to remove/demolish the kitchen when he took off the roof, so would obviously be much less disruptive. The second guy said it would be impossible to save the kitchen from water ingress when removing the roof, without getting a very expensive scaffold roof and said we would need to remove and then reinstall the kitchen, again leading him to the conclusion that we would be better off knocking down and staring again.

Any thoughts on this- I have provided some photos/plans

Sorry for long email- in summary
1) Are the footings likely to be good enough for a 2nd storey?
2) Are we better off using the existing 2.5 walls (if footings good enough)
3) If adding to existing extension do old walls insulation need updating to meet current building regs?
3) Can we keep (ideally using) the kitchen while building works are going on?

THanks

Jamie

 

[^woody^]

How have builders quoted if you don't have detailed plans and specifications?

Never let builders quote on nothing just an idea, or what they think or what they would like to do. Those are not quotes, or even estimates, they are dreams - which become nightmares.

Speak with someone who can design it, to what you want and would like to pay. Get a design approved for all required permissions, then get your quotes.

Generally, it's cheaper to use existing walls and foundations if the resulting new rooms will perform and meet your needs.

Yes you can keep some sort of kitchen while the work proceeds around it. However, if there are time factors for the builder, then there may be costs for you. You need to weigh up the options and the builders quote cost comparisons for working in a particular way.

 

[JayBo1979]

Thanks for your reply, Woody, I have an architect working on plans, and he never mentioned any of the above potential issues. I wanted to speak to a couple of builders to get a very rough idea of costs, to see if I can afford an extension of this scale. I realise that without concrete plans then its impossible to get a detailed quote. My issue is they said totally different things buy I wonder if builder2 just was chasing a bigger job or didn't really want to do it

 

[JayBo1979]

Has anyone got any further advice on this?

 

[Mottie]

It may be because I’ve just got up but I can’t get my head around the footing dimensions. I can understand 600mm wide and 1 metre deep but I don’t understand the 250mm thick part of the dimension. What is the 'thickness'? Are they a type of square pile?

 

[noseall]

It may be because I’ve just got up but I can’t get my head around the footing dimensions. I can understand 600mm wide and 1 metre deep but I don’t understand the 250mm thick part of the dimension. What is the 'thickness'? Are they a type of square pile?

The strip footings are 600mm wide and set at a depth of 1m down from ground level. They were cast at 250mm thick.

Personally, we would have mass filled. I'd have thought 250mm thick would just about cut it, on good ground.

 

[JayBo1979]

This is relevant part of the building control doc

 

[noseall]

This is relevant part of the building control doc

The fact that they are 600mm wide, is a boon.

 

[JayBo1979]

Looking at the construction of the extension wall it’s the following:

100mm concrete outer block
100mm? thermolite block inner
25mm DR therm polystyrene slab cavity clipped to inner skin

Is this ok to build off and would the insulation need to be upgraded if incorporated into a new extension?

Thanks for all your help

 

[Mr Chibs]

Mates' extension has been told to do: 100/100 cavity/100 and 40mm PIR on internal skins for the new regs in lieu of 150mm cavity.

 

[^woody^]

Thanks for your reply, Woody, I have an architect working on plans, and he never mentioned any of the above potential issues. I wanted to speak to a couple of builders to get a very rough idea of costs, to see if I can afford an extension of this scale. I realise that without concrete plans then its impossible to get a detailed quote. My issue is they said totally different things buy I wonder if builder2 just was chasing a bigger job or didn't really want to do it

What you, as the client should do is tell the people you employ what you want and they quote for that.

So starting with the designer you tell him what you need or want from the extension, and how much you want to spend and they design to meet those requirements.

Then when you give those plans and specifications to a builder, they are quoting for the exact same thing. So quotes are comparable in that respect.

Then what you also do, is tell the builders your requirements in terms of the building process - need to use the kitchen, must be finished by a certain date, and such like, so again they quote on the exact same process.

If a builder makes a suggestion that you like, or gives you options, then yes you ask for that to be priced in the quote, but you also must ask all the other builders quoting to do the same. That way, every single quote is comparable and any price difference is nothing to do with the work or specification - ie you get the same thing whether you pay £10k or £100k.

 

[^woody^]

This is relevant part of the building control doc

That's classic 1970's plan drawing right there.