Foundations quote

[oldkettle]

Hi,

 

Just had a quote for the foundations and services for our outbuilding. Seems on the high side to me - can you please have a look? South East.

 

I will check how much insulation they quoted for because they omitted this little detail, but there are a few things I don't quite understand.

1) What are prelims - on top of setting up and SE work.

2) why do they need 2 skips (at an inflated price from what I can see) if there is no demolition involved, the only thing to get rid of is probably formwork?

3) 50m excavation (in our back garden, I think the number is slightly high) looks like a 2 day job for a mini-digger and probably less for a trencher? 

 

Obviously, no idea about the main item as the cage size may be quite large due to Lawson's cypress in 2m, but mesh seems to be about £600 for 2 layers + cages, the main slab is about 5m3 of concrete + way more on the toes at £100+m3. 

 

TA.

	Quantity		Unit Value	Total
Raft Foundation
Set up and enable site	1	item	£ 300.00	£ 300.00
Supply structural engineers design and calculations	1	item	£ 850.00	£ 850.00
Cut and fill ground to accommodate a 6x9m raft foundation	54	m2	£ 20.00	£ 1,080.00
Supply and lay HEXATHERM XFLOOR 300 (insulation) under raft foundation	54	m2	£ 62.00	£ 3,348.00
Lay hardcore sub base, install timber formwork, install 2 layers of A393 steel mesh with perimeter toe steel cage. Pour RC35 concrete for a reinforced slab as per Structural Engineers design	54	m2	£ 160.00	£ 8,640.00
Supply concrete pump	1	item	£ 800.00	£ 800.00
6 yrd skip	2	nr	£ 330.00	£ 660.00
Services
Excavate trench and install 110mm foul pipe, include connection into exiting chamber	49	m	£ 55.00	£ 2,695.00
Additional chambers and back drops	3	items	£ 450.00	£ 1,350.00
Supply and lay 25mm water pipe to open trench (connections by others)	49	m	£ 6.00	£ 294.00
To terminate by corner of house
Supply and lay 65mm electric duct	49	m	£ 7.20	£ 352.80
To terminate by corner of house
		Sub total		£ 20,369.80
		Prelims @12%		£ 2,444.38
		Total (excl VAT)		£ 22,814.18

[oldkettle]

80mm insulation for £3348. Nice.

[Mr Punter]

Your prelims are for managing the job, RAMS, PPE etc.  May also be for overheads costs and profit.

Skips - for concrete pump washout?  Offcuts from insulation.  Packaging.  Pallets.  Pipe and duct offcuts.  Tree roots.

Not sure how deep the foul is going but it doesn't sound crazy.

Can you exclude any of these from their works and do yourself?

At least now you have prices and quants you can compare to others / look at SPONS.

 

[Russell griffiths]

I would do a bit of re, thinking. 

Why hex a therm, it’s possible the dearest insulation you can buy. 

Why timber shuttering, if you use one of the insulated slabs with the upstand you don’t need shuttering. 

 

If you look look at what sort of price people have paid for their house slabs your one is very expensive. 

 

There was a post a week week ago regarding cost for a slab, I think from memory it was on average £145-175 a m. 

With ground works on top of that. 

 

That hexatherm is £60 a m ??? I would leave that to the big civil engineering companies. 

 

Edited August 19, 2020 by Russell griffiths

[oldkettle]

1 hour ago, Mr Punter said:

Your prelims are for managing the job, RAMS, PPE etc.  May also be for overheads costs and profit.

Skips - for concrete pump washout?  Offcuts from insulation.  Packaging.  Pallets.  Pipe and duct offcuts.  Tree roots.

Not sure how deep the foul is going but it doesn't sound crazy.

Can you exclude any of these from their works and do yourself?

At least now you have prices and quants you can compare to others / look at SPONS.

 

 

Prelims - you are probably right, but this looks really steep to me - this is a company specialising in ground works and "managing the job for 10%" is something an architect charges for getting to site once a week. Anyway, won't be questioning this number.

Skips were apparently for timber shuttering and steel offcuts. I thought concrete wasn't allowed in a skip? Anyway, they are happy to leave rubbish in place  

Foul would probably go to a minimum required depth, our site is sloping in the right direction at about 1m in 15 so may need to be slightly deeper at the start to arrive back to the house with 1:40 fall. I guess the trench needs to be deeper for the mains water anyway. Am I way off with my 2 days estimate?

 

They are quoting chambers and back drops at £450 a pop - seem to cost about £200 normally? Surely doesn't take a plumber half a day to install each of them?

 

I wanted an idea about the cost. £27K (inc. VAT) makes the project not viable. £10K - as Russell has referenced and which I kind of hoped for - would have been more like it. Will obviously get more quotes. 

Edited August 19, 2020 by oldkettle
typo

[PeterW]

6 minutes ago, oldkettle said:

They are quoting chambers and back drops at £450 a pop - seem to cost about £200 normally? Surely doesn't take a plumber half a day to install each of them?

Sounds about right. Chamber will be £150, benching and backfill, excavation etc will be about right. If they have to do external backdrops then these take a lot more effort and bits to make them work. 

[oldkettle]

1 hour ago, Russell griffiths said:

I would do a bit of re, thinking. 

Why hex a therm, it’s possible the dearest insulation you can buy. 

Why timber shuttering, if you use one of the insulated slabs with the upstand you don’t need shuttering. 

 

If you look look at what sort of price people have paid for their house slabs your one is very expensive. 

 

There was a post a week week ago regarding cost for a slab, I think from memory it was on average £145-175 a m. 

With ground works on top of that. 

 

That hexatherm is £60 a m ??? I would leave that to the big civil engineering companies. 

 

 

You are certainly right

I found the first company around here who have insulated raft on their website. Wanted to get an idea of the cost. They completely ignored my "300mm EPS" message, no idea why hexatherm has been quoted.

 

Yeah, I went through several posts about the slabs including DIY ones and saw the guide prices you mentioned, just hoped to find something with a reasonable price here, otherwise my wife will switch back to "we should rent"  and I really don't want to live in an apartment ever again: even caravan sounds better to me.

Edited August 19, 2020 by oldkettle
typo

[oldkettle]

5 minutes ago, PeterW said:

Sounds about right. Chamber will be £150, benching and backfill, excavation etc will be about right. If they have to do external backdrops then these take a lot more effort and bits to make them work. 

 

I thought excavation for the whole trench was a separate item anyway? Or is more work required specifically for chambers?

 

With regards to backdrops, I read a bit on pavingexpert and not sure whether this applies, as I'd expect only the "source" in the outbuilding and a single connection to the existing system, this may be the place where one is needed? But again, "include connection into exiting chamber" is a part of the excavation line.

[PeterW]

Set of plans would be useful to see what they are suggesting ..? 

[oldkettle]

Sorry, there are none: he came around to look at the site, took some measurements and provided a quote in a few days.

 

The project is to build a 9x6 gym at the top of our garden, and take services there (and foul water back). This company has quoted for the groundworks part. As I said, there is a fall of about 2.5-3m from the top point towards the house and the distance is about 40m. There may be a gentle turn or two on the way to arrive at the corner. Attached is a very very rough drawing of what needs to happen.

 

 

[PeterW]

So without knowing the invert level it’s difficult to say but not sure why he’s quoting to put back drops in ..? If your invert at the house is say 600mm, start at 1.2m at the back and you’ve got about a 1:20 fall across the drains. Nothing too dramatic. Needs an IC half way down but that’s all. 
 

9 minutes ago, oldkettle said:

The project is to build a 9x6 gym

That’s a very big gym..!!! What is the construction method planned and whats the access to the back garden ...?

[ProDave]

My first thought is why a solid floor?

 

Timber building with timber floor set on a few concrete pads, vastly simplifies the groundworks, small amount of concrete is barrowable so avoids the concrete pump, hardly any soil to lose, you could probably lose it on site, avoids the skips etc etc.

[oldkettle]

@PeterW, @ProDave

 

Well, I am not sure about concrete, but since we want to live there during the build I thought making it into a well insulated one would make sense. I do indeed want to use it as a gym eventually (and the kids have other ideas for the extra space) and want to avoid cold floors in winter and really hot air in summer. Yes, it would be way more economical to use pads, although due to the proximity to the trees these may have to be really deep (with this size I have to involve BC).

With regards to the build method, I started with SIPS as one of the producers was happy to quote for both the extension and the outbuilding, but right now I am seriously thinking about ICF: 30m perimeter, one floor, must be possible to DIY in a reasonable time. Don't need anything special inside, just MDF or plywood, a couple of internal walls. I am not sure at all about the heating and hot water though  but one problem at a time.

 

There is access for a mini-digger on the right of the house, just over a meter wide. There is also an option to create an opening at the back of the garage, then obviously a larger digger would be possible (although the height may become a limitation). I did a quick search and it seems due to the very limited excavation any mini-digger should be able to handle it.

 

1 hour ago, PeterW said:

So without knowing the invert level it’s difficult to say but not sure why he’s quoting to put back drops in ..? If your invert at the house is say 600mm, start at 1.2m at the back and you’ve got about a 1:20 fall across the drains. Nothing too dramatic. Needs an IC half way down but that’s all. 

 

Peter, this is what I thought about the drains. Even if it is required in one place, certainly shouldn't be 3. Seems just a way to inflate the quote to me - but again, this is why I ask others to advise, don't know nearly enough.

[Mr Punter]

Backdrops not required.  Given that this is only a gym I would want to reduce the cost by 40%.  EPS insulation is fine under the slab and if you DIY will save 70%.  You may get a more economical slab design.  The £4,700 for the trench and buried plastic seems steep.  With the prelims, because they are a percentage these should come down as well.

 

Just use this as an initial quote and look at savings that can be made.

 

Because it is a fair sized slab you will need someone competent to pour and finish the concrete.

 

Regarding the build method, why not blockwork cavity walls with insulation?  Does not need to be passive standard, just normal batts or partial fill pur.  If you are keen to muck in you could load out the blocks for your brickie.  You could have the brickie and his mate do a day a week and they would do it in no time. 

[oldkettle]

7 hours ago, Mr Punter said:

Backdrops not required.  Given that this is only a gym I would want to reduce the cost by 40%.  EPS insulation is fine under the slab and if you DIY will save 70%.  You may get a more economical slab design.  The £4,700 for the trench and buried plastic seems steep.  With the prelims, because they are a percentage these should come down as well.

 

Just use this as an initial quote and look at savings that can be made.

 

Because it is a fair sized slab you will need someone competent to pour and finish the concrete.

 

Regarding the build method, why not blockwork cavity walls with insulation?  Does not need to be passive standard, just normal batts or partial fill pur.  If you are keen to muck in you could load out the blocks for your brickie.  You could have the brickie and his mate do a day a week and they would do it in no time. 

 

You said 40% off - I thought the initial price was twice what I expected  nearly there.

 

Yes, I won't touch concrete whatever happens.

 

WRT cavity wall, not sure it would save me enough. If I spend 10K+ on the passive foundations with services it probably makes sense to complete this properly. SIPS panels and ICF seem to be £50/m2, I need about 30*2.4=72m2, doesn't seems to make a huge difference, maybe insulated b&b would be 3K rather than 4K here? Or am I well off here?

[Mr Punter]

I thought site access was bad, so smaller units would be easier to move.  Blockwork is good as it will not rot.  You could do a single skin of 140mm medium density blockwork, left fair faced internally with external EPS insulation and thin coat render on the outside.  You could DIY the insulation if you wanted to save money.  A pitched roof is likely to be lower risk.

[oldkettle]

17 minutes ago, Mr Punter said:

I thought site access was bad, so smaller units would be easier to move.  Blockwork is good as it will not rot.  You could do a single skin of 140mm medium density blockwork, left fair faced internally with external EPS insulation and thin coat render on the outside.  You could DIY the insulation if you wanted to save money.  A pitched roof is likely to be lower risk.

 

well, the access is not too bad - surely can get 1.2*2.4m panel through easily and for ICF this wouldn't be required. But can't do without a pump.

 

Roof I certainly want pitched, need more height for the gym  

 

I remember single skin construction was discussed here a while ago. Need to try and find robust detail for it, see whether there is a way to have an uninterrupted insulation layer with the roof. Also make sure rats are easy to keep away - a building which in not used 24/7 will be under constant threat.

[ProDave]

If the old bungalow is coming down, why not take the garage down now and you can then get through with a dumper for pouring concrete etc.

[oldkettle]

20 minutes ago, ProDave said:

If the old bungalow is coming down, why not take the garage down now and you can then get through with a dumper for pouring concrete etc.

 

The bungalow is not coming down fully, PP is for an extension.

Do you mean a dumper truck? This is a big beast.

When talking to builders I always tell them I am open to suggestions regarding access. £800 + VAT for a pump isn't a small change but rebuilding a garage is not going to be cheaper.

[ProDave]

Take the garage roof off. Leave the side wall standing. Take down the rear garage wall.  That will give you vastly better access for all the building work.

 

When done, fit a garage door in the back, always handy to have through access to the garden, and fit a better pitched roof to give storage above the garage.

 

Otherwise you will need the concrete pump again for the extension build, and getting materials through will be harder, and everything will have to be done by hand or with a tiny digger.

[JFDIY]

£300 for a pump (often with with operator) is the norm round here.

[oldkettle]

1 hour ago, ProDave said:

Take the garage roof off. Leave the side wall standing. Take down the rear garage wall.  That will give you vastly better access for all the building work.

 

When done, fit a garage door in the back, always handy to have through access to the garden, and fit a better pitched roof to give storage above the garage.

 

Otherwise you will need the concrete pump again for the extension build, and getting materials through will be harder, and everything will have to be done by hand or with a tiny digger.

 

Absolutely, there is a window in the rear garage wall, an opening can be created there as well. Depends on what needs to go through - what type do you think is required? I thought a  1.5t digger would be enough as there is very little to actually dig so didn't worry too much as it's only about 1m wide.

The garage roof will have to come down as it a corrugated asbestos cement one, for now it's a storage + while there is a door it add security. I was planning to do it when the main building works start as will probably make putting scaffolding there easier.

Edited August 20, 2020 by oldkettle
typo

[oldkettle]

50 minutes ago, JFDIY said:

£300 for a pump (often with with operator) is the norm round here.

 

it may well be - I didn't check, the only link I found was https://www.hanson.co.uk/en/ready-mixed-concrete/technical-information/concrete-pump-faqs

>> Concrete pump hire costs can vary but, as a guide, expect to pay around £300-£400 on top of the price of the concrete.

 

If this is the case 800 (+ VAT) is another nice little earner. Or rather not.  

[Russell griffiths]

This is the difference between using a main contractor or booking trades yourself. 

I paid £600 for the biggest pump you will ever need, but if I booked it to pour your slab I would put 10-15% on top. 

I would also do the same for all materials. 

[oldkettle]

18 minutes ago, Russell griffiths said:

This is the difference between using a main contractor or booking trades yourself. 

I paid £600 for the biggest pump you will ever need, but if I booked it to pour your slab I would put 10-15% on top. 

I would also do the same for all materials. 

 

10-15% I'd accept. It's 800 vs 400 (+12% prelims) which I find OOT.