Concrete Foundations

Costs of Concrete Foundations

Q - What are the cost and practical implications of using ready mixed or site mixed concrete?

A - On small projects such as single or extensions houses it is just not worth the bother of site mixing concrete. Ready mixed, delivered to the site, will cost more but will save you both time and back ache. On larger projects, savings of up to £15 to £20 per cubic metre can be achieved by site mixing but only if substantial volumes of concrete are involved to justify the setting up of the batching plant.

Q- We hope to commence work on our large house extension shortly and are wondering about the concrete foundations. Should we mix the concrete on site or have it delivered ready mixed? And what are the cost implications in these options?

A - On small projects the volume of concrete in the foundations is relatively small but the physical effort required in site mixing and placing the concrete is considerable. You will probably have to an extra £10 to £15 per cubic metre for ready mixed but this is a small price to pay for the convenience of tipping the concrete by chute directly into the trenches.

Q - I am about to build a three-storey detached town house in North Wales. The site has some old brick church foundations on it that will encroach on the new footprint of my house. How much of a problem would you expect this to be and what should I be paying for 60 square metres of slab foundations and drains?

A - For a 60m2 of concrete slab foundations sized-house you should expect to pay £5,000 to £6,000 for the foundations and slab and about £3,500 for the drains in normal ground conditions. Unless you are building directly over the existing foundations (as opposed to crossing them here and there), the extra costs should be insignificant.

Q - What is the difference in costs between strip foundations with a concrete slab and concrete filled trenches and a slab for a house size 170 square metres?

A - The concrete slab applies to both methods of construction and should cost about £3,500. A concrete strip foundation plus brickwork should cost £ 3,250 and filling the trenches with concrete should be £4,250 so you can see that the traditional method of strip foundations and brickwork is the cheaper option but it takes longer to construct.

Q - A contractor is building the foundations and shell of our house. He is currently up to eaves level and has asked for 80% of the total quotation but this seems a little excessive to me. What do you think?

A - This shows the importance of agreeing the method of payment before starting. The following percentages are typical for this type of work.


Q - We have permission to build a four-bedroom house on clay soil with adjacent mature trees. We have been advised to mini-pile the foundations and use pot and block flooring. Can you give us some guidelines on the likely costs of this work?

A - Piling is a highly specialised form of construction and the nature of the ground and weight of the building to be supported will dictate the depth and number of piles required. So you must obtain quotes from a specialist firm. For the pot and block flooring I would allow £50 per square metre.

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