Thanks for the breakdown of costs but in my case there are extra costs that need factoring in. For instance the soakaway would need to be dug into an embankment that is almost 1m higher than the ground level of the house. The embankment is held back by a retaining wall. Building Control have stated that the soakaway would need to go down 2.3m with at least 1:40 gradient and need a 1 cubic metre soakaway crate. On the internet a crates this size are priced somewhere in the region of £200. The soakaway would need to meet design BRE Digest 365. I have had landscape gardeners, builders and drainage companies round to quote me a price and they have all stated that this would be a major job costing in excess of £1000. Out of the quotes I've had already, they range from £1300 to £2500 so even if you factor in adjustments such as loss of profit etc, I still find it difficult to accept £500 as being a reasonable amount to deduct from the overall price. I think what I am going to do is take an average of the three lowest quotes (minus adjustments) and ask the builder to take this amount off his bill. Does this sound fair?

Well I may believe what you are saying is true except for one thing. My builder charged me £3000 to dig a 1m deep 5m trench for footings. That included waste removal and 4 cubic metres of concrete. Even if the concrete was around £500 and a grab lorry was say £500 that still leaves £2000 labour for just digging the same size hole! Unless I'm missing something I'm not sure why the costs would be so different. Any thoughts?

Also there is no provision for "loss of profit" in our contract so can he really claim for this?

Thanks for your reply. It was the builders suggestion that the work should be done at a later date and so we agreed to remove the item from the overall costs. The builder hasn't started any work on the soakaway so how would I know what claim for "loss of profit" was reasonable?

Other builders are actually quoting higher (more than double) because the amount of work involved is quite extensive. The reason why I believe my builder is quoting such a low amount is because he needs to deduct it from the overall amount that I have yet to pay him. The soak away can not be done as part of the work he is doing until some other construction work that he is not contracted to perform has been completed which is some way off. Because of this he has agreed to deduct the cost of the soak away from his bill and I feel that he is not being totally honest and fair with me when it comes to pricing this up.

I have a builder who has almost finished an extension on the back of my house. The only remaining task was to build a soak away which was included in the original quote. However, we both came to an agreement to remove the soak away from the quoted list of works as it was no longer required but the only problem was that this item was not explicitly priced in the quote so there is some dispute over how much should be deducted. The builder is adamant that the soak away will cost £500 and is not willing to accept other quotes from other builders. I still owe him some money so where do I stand on this? Am I in my rights to deduct from what I owe him the cost of what other builders would quote for a soak away?