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Water drainage and footway design


Ann

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Hello, this is my first post and my first experience as a self-builder. Currently at the RM planning application stage for a four-bedroom house on a good size plot. The outline planning approval included the conditions to provide details of the land, foul and surface water drainage arrangements, plus a detailed scheme to increase the footway along the site frontage.

 

I've received a quote for the water drainage design and the footway design (both by same company), but the cost seems quite high. I'd welcome any advice about the cost of this work as I don't have anything to compare it to and, at the moment, can't find another company to quote.

Edited by Ann
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Hello Ann,    Welcome.

 

Welcome also to the type of problem that you will have with almost every expenditure heading. And the answer is leg-work; or networking to give it another name.

Many here use the global build cost of between £1500 and £1300 per square meter. Put the numbers you have for the drainage in context first: it may be that special circumstances exist where you are - rock - sandy soil - boggy ground. 

 

But that doesn't help you with the current issue. @PeterW's post above is the one that needs answering first. 

Generally, the answer starts with the process of asking as many people as possible for their advice. Don't be shy.

Ian

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The building plot is 18 m by 40 m, in a village. The plot was part of the garden of a neighbouring house. The plans are for a detached four-bedroom house.

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Thanks for the advice. I've been looking at posts about the build cost per square metre. So far I've only had the planning and architect costs. The drainage and footway design quote just seems quite high at £2,500 plus VAT. Or is that reasonable?

 

I'll try to post some plans later.

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By the sounds of it the council are asking for an 18m footway along the front of the plot. 

 

If thats at a standard 1100mm wide and built up to council spec (ie concrete edging both sides, 150mm MOT1, Tarmac top coat to 65mm) then you will be looking at circa £100 a metre. 

 

If they’ve asked for it to edge to the road and have a road kerb detail with dropped kerbs for your driveway then you could double that if they also need a roadworks licence and a road edge to make good. Main road could add traffic lights so add £2k. 

 

Drains are an unknown unless you’ve got a drain plan and can advise if  it includes the main sewer connection ..?

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The council has only specified that the footway has to be widened by about 500 mm to 1800 mm and a drop kerb is required. I need to submit the plans to be approved with the RM application. It's not a main road; just a quiet road in a village, parts of which don't even have a footway! I challenged the council on this during the outline planning application, but other developments in the village have had the same condition applied to widen the  existing footway.

 

The drainage design includes the main sewer connection.

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@Ann welcome! Perhaps consider the implied hourly rate of the cost. How many hours might the job take for an experienced engineer? And is is just desk work or is surveying required? 10 hours for example would imply a £250 hourly rate, which I would consider extremely generous.

 

Do also note that the VAT will not be reclaimable from HMRC at the end.

 

Finally, its good advice to always get three quotations, every time.

 

Edited to add: slightly off topic, as a shortcut I try to extract an hourly rate from all the contractors (professional and the trades), if only for comparison purposes. It gives me an ability to compare their value-for-money as I perceive it in a more equivalent manner and even between disciplines. And I find it avoids mismatches in expectations on financial matters between them & I. I can then compose my team on a value-for-money basis based on my own priorities.   

 

For example, I did this exercise across architects and am just about to select one that is every bit as good than the others (and in some ways better in their knowledge of Passive Hosue for example) but has an hourly rate that is half that of the priciest one. I expect that in the longer term this will lead to a more harmonious relationship, with fewer rankles over fees.

Edited by Dreadnaught
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It's definitely for design only. I'm now getting another quote!

 

Many thanks for the input. I'm just starting out so I'm sure I'll be posting more questions in the future!

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You may not need anyone to do the drainage design, at least not for planning purposes. You might be able to write it up yourself but it depends on a few things.. 

 

Is there a sewer in the road? In which case you might only need to say: "Foul drainage will be connected to the main sewer in the road, details to be agreed with Building Control". If there isn't easy access to a sewer then they will want details of the sewerage treatment plant you propose to use. There are people on this forum that can probably recommend one.

 

What sort of soil do you have and do you know if soakaways work?  On free draining soil you might get away with saying that "The ground is free draining and rainwater will be discharged to soakaways, dimensions and locations to be agreed with Building Control". If you are on clay or soil that's not free draining you might need to prove that soakaways will work. This is usually done by doing a "percolation test" which involves digging a hole and filling it with water. There are "site investigation" or "ground works" companies that will do this. If you also need a "soil condition report" to design the foundations you can save money by employing the same company to do both at once. Can also save money if you provide the digger and driver. 

 

So best case you might only need to write a short letter to satisfy the planners and more details for Building Control later.

 

 

Edited by Temp
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