underpinning - is there an alternative?

old_trout

hi, hope you can help. building inspector said the footings on my ground floor extension are only 40cm and need to be 1 m. I want to put a 1st floor on it but extension is attached to a conservatory. I was told I could have a metal/rsj type structure built with pilings instead. has anyone heard of this alternative? and what would be the approx. cost. the extension is 8 x 4 m approx. I know normal underpinning costs are approx £1000 per metre. thanks for any advice. deb

Furts

The underpinning cost sounds horrendous - is this the going rate in your area of UK? This does not appear the best way of costing your job. You need a proper design and proposals.

If you undertake the underpinning, or get labour in, or project manage it can be done for reasonable sums. To give an idea, two men have hand dug and concreted foundations for MIL extension, size about 4500 x 2500, so around 9000 length of trench. This was done in one day. So around £300 for labour and £300 for concrete. The men worked like demons - I had allowed two days for the work.

With the piles and steel costs - how long is a piece of string? These will need design, plus design for the ground beams above, then a design for a steel frame above...this is all specialist work and bespoke to your home. Piling is specialist work and the cost depends on mobilisation, competition, demand for work, number of piles, depths of piles...etc.

brightontraveller

To cost a dig without knowing soil conditions, access, waste removal charges etc is fool hardy the above for example does not include waste removal ???

As a general rule of thumb 1st storey £1000 - 1500 per m²
2 storey extension the upper floor would be an additional half of the £ per m². Much of the building work required for 1 storey is only needed once no matter if is 1 storey or more, such as the foundations and roof. This cost can be increased if repositioning of services gas, water, electricity, drains etc are needed and dependant on materials used
Apart from construction other costs you will incur as part of your project. Fees for architects, engineers, planning and building regulations etc can add on a possible 10% – 20% on top of the build costs

Easiest way if add your meterage required if that is still in budget progress to architect and builders quotes etc