Please comment on prelim.budget

[Bored Shopper]

We're at SE plans stage with our 242 sq m "box with basement" (c.180 sq m without basement). 

 

A recommended main contractor issued a preliminary (pretty ballpark) costings budget. We are combing through it but definitely need experienced pair(s) of eyes to see where it gets ridiculous.  We'd love to have a basement but may be forced to drop it if it proves prohibitive.

 

Any comments on the budget would be much appreciated. 

(NB: we'll have a PM to manage this, minimal own labour, and we're within M25 in Greater London (woe!). An existing old bungalow to be demolished. The plot is flat, service connected, no crested newts / sandy ground / major rivers etc).

 

 

[Bitpipe]

Basement cost looks high - we built a 110m2 basement (inc demolition & all drainage & services for house) for £120k in 2015 in Berkshire.

 

Have you had ground investigation to spec the basement design (loading, water/gas monitoring / substrate analysis)?

 

SE can only design basement (inc waterproofing strategy) when you have that and you can only get it costed when the SE has designed it.

 

[ProDave]

Exclude the basement, and you get £242,060 for 180 square metres, which is £1344 per square metre which is good.

 

£162,450 for a 41 square metre basement is £3962 per square metre.

 

you would really really REALLY want need that extra space and not able to get that extra space any other way to pay that much.  (that basement is costed at more than my whole house build!!!)

 

Electrics at £11,250 is on the steep side for me.

[recoveringbuilder]

All I can say is thank goodness I’m not in London ?

[PeterW]

Electrics and mechanical are steep - should be max 2/3rds that even in London pricing. Windows are mental for standard uPVC unless you’ve got 10m bifolds that you’re hiding ...!! 

 

Basement - get another quote as that seems very expensive.  

[Ferdinand]

I would suggest coming up with your own estimate for the exclusions to get a ballpark total, and for the bits you have commissioned ... architect, future PM etc. And get your total figure. Another 150k?

 

Agree on another quote, and perhaps an online service QS too? Perhaps a quote by a package supplier, such as a TF company with a higher spec.

 

Ferdinand

 

[Declan52]

Would be cheaper and easier to put a room in the roof so you have 3 floors instead of the basement. The 3rd floor would have more useable space. 

Are you restricted with the height of your ridge???

What type of 100mm cavity wall insulation are you planning to use to meet building regs??

 

[Bored Shopper]

15 minutes ago, Declan52 said:

Would be cheaper and easier to put a room in the roof so you have 3 floors instead of the basement. The 3rd floor would have more useable space. 

Are you restricted with the height of your ridge???

Sadly, we are very restricted height-wise, as our first option, killed mercilessly by the council, was a nice room in the roof. We are in a street with 50% bungalows and it massively ties our hands. Hence the option to dig down rather than build up. Also the garden is small so not much room for another outbuilding for storage there...

[Bored Shopper]

9 hours ago, Bitpipe said:

Basement cost looks high - we built a 110m2 basement (inc demolition & all drainage & services for house) for £120k in 2015 in Berkshire.

Have you had ground investigation to spec the basement design (loading, water/gas monitoring / substrate analysis)?

SE can only design basement (inc waterproofing strategy) when you have that and you can only get it costed when the SE has designed it.

 

yes we've had 2x holes drilled, SE came and had a good look at both and a report on paper is pending, so maybe something would change (for the better).

[Bitpipe]

10 hours ago, ProDave said:

£162,450 for a 41 square metre basement is £3962 per square metre.

 

Our 110m2 basement was £1000/m2 before fit out (plastering, flooring, electrics, doors etc) and that included demolition of existing and water, power, telco, drainage to the plot.

 

They key is to avoid any contractor with basement in their title. it's just a RC box in the ground and any competent groundworker can build one (they usually sub out the concrete works to a specialised crew). These crews are building underground car parks, etc all day long for developers so you're nothing special.

 

SE will spec the necessary waterproofing requirements, if ground water is below the basement then a land drain to the perimeter and warrantied waterproof concrete (e.g. Sika) will suffice - no need for membranes or sumps & pumps. Site access and space will also impact cost as will the muckaway depending on whats in the ground ) clay, gravel, chalk etc.

 

It's a great use of space on site and the best rooms you will have in your house - cool in summer and warm in winter. No heating required if you build off an EPS slab and clad external walls in EPS. Ours have 2m wide high level windows in GRP lightwells and are as bright and sunny as any room in the house.

Edited July 9, 2019 by Bitpipe

[Tony C]

Very interesting for me as I am waiting to receive quotation from 4 contractors in a few weeks! Our house is in London also, single story 150m2 including small basement (25m2)

 

Our basement is a little different as it is  2/3 basement + 1/3 above ground level, but I share QS estimate for the basement shell here.

Will you be using PM who hire collection of subs instead of single contractor?

 

 

 

 

 

[Temp]

One possibility would be to hire a QS to go over the cost estimates but that in itself can be expensive.

 

I noticed rather a lot of figures like £12,995 and £13,995.