Building a garage and Kitchen Extension

[sandman77]

I am in the early stages of planning a house extention that will incorporate a garage and kitchen extension. I plan on doing the build in stages (for financial reasons).
Firstly I will be be digging and pouring the foundations and building up to FFL and pouring the slab. The FFL will be roughly 1m above existing ground level. The build will then stay at this stage while I get the finds together for the next stage.
Stage 2 will be to build the shell of the extension and make watertight (roof/windows/door). Once this stage is complete I plan on using the Kitchen extension part of the building as a garden store untill next summer when I will knock through into the kitchen and brick up the existing back door to the house.

Is this feasable? Can you see any problems in doing things this way?
The extension will be a standard block and brick build and I will get a brickie in to do the brockwork but I plan on digging and pouring the foundations myself. For costing purposes what size of foundation should I go for? Is a 350mmx350mm strip enough for this type of build? I suppose I should build it so I can, in the future if I want, build a 2nd story on top.

Untitled

• sandman77
• 15 Feb 2011
• 1

 

[RedHerring2]

You'll have to build it according to Building Regulations, and it would probably be easier to submit plans for BCO approval prior to beginning.
The alternative is starting on a Builders Notice, when plans are not submitted, but in your case you'll need to know what is wanted/needed before you do it, and then seek approval at each stage.

I would suggest that 125mm extra either side of the blockwork would be required for footings, assuming 100mm blockwork, 100mm cavity, 100mm blockwork, your footings will need to be 450mm wide, at a guess. At least 275mm thick. Depth is due to local conditions.

If you submit plans and have them approved by BCO, they are approved at the current regulations, even if it takes you 5 years to build and they change in that time. Also, you'll know what is required rather than relying on guesswork.

Your phases sound perfectly acceptable to me.
You might need to watch out for frost damage at certains time and places, e.g. water in the cavity freezing and damaging the wall, deterioration of insulation, frost damage to blockwork, etc.

Sounds like you'll also need SE calculations for steelwork when you knock through. This will aslo need BCO approval.

 

[noseall]

I can't foresee any problems with your scheduling arrangements. Builds are often left at slab level and/or watertight stage and are popular cut-off points.

Foundations will depend upon how you wish to build.

A typical cavity wall achieving 0.3 u value would consist of 100mm outer skin, 100mm full fill cavity (dri-therm etc) and 100mm aerated block inner skin. Typical foundations would be 600mm wide, a minimum of 225mm thick (or mass fill for ease) and 1m deep.

 

[RedHerring2]

I'm just a DIYer so take more notice of Noseall's advice than mine.

 

[noseall]

I'm just a DIYer so take more notice of Noseall's advice than mine.

Looks like good advice to me Red, and you pipped me this time.....