Quote for groundworks is really high! - help and opinions needed please

[AjitSingh213]

Hi All,

 

I am a self-builder and I need help! 

 

Short story is: I have planning, got a self-build mortgage in place (only drawn down money to buy the land so far), was working with a turnkey house provider to build a Timber SIPs home (tight ish site), they were going to do from planning to giving us the key, they did the SE for groundworks (insulated concrete raft slab - passive), drainage/services and retaining wall and got quotes for groundworks which were way higher than expected so we are parting ways (along with several other reasons) with them so we can be more flexible on costs and take on some more stuff ourselves (we are nervous about this!). 

 

The question I have is what a reasonable ball park cost for groundworks, demolition (2 small single story barns), site clearance and securing the site, foundation, drainage/utilities and retaining wall might be? For my work I was quoted £175k and I am finding it hard to believe that this is reasonable for the size of our plot (120sqm GIA – 10m x 8m footprint, 80sqm garden space) - maybe it is but from indicatively speaking to people in the trade, they don't seem to think so?

 

I have full planning drawings, in a residential area so utilities is close by, it is on a slight slope and we are digging down to get a 2 storey house in (planning requirement), retaining wall is on average less than 1m high most of the way round the boundary (30m in length). I don't have the SE drawings yet, we are going to pay for those as part of our termination and will receive them shortly (previous company used them to get the quote), ground investigation done with no major concerns on ground conditions. 

 

We are currently exploring using a different builder all together for the house and have had estimates already for groundworks which are significantly less (although they do not have the structural engineering or drainage design so we understand this could change massively although their estimates are based on their SE reviewing the plans and coming up with an estimated price).

 

We understand that there are a lot of variables, we understand we don’t know what we might dig up and we know that no site is the same but we are just trying to understand 

 

1)    Whether anybody has had similar experience to us and if so, what action did you take? 
2)    Whether anybody has any general advice on what the best next steps are and any thoughts on the price provided? 
3)    Whether anybody can share their groundworks costs so I can make rough comparisons or express their opinions on the price quoted?

 

Any help would be greatly appreciated! Some images and sections of the site and house plans are below

 

Thanks in advance

 

 

 

[Kelvin]

You need to get several quotes but you also need your full SE foundation design and drainage plans. None of the groundsworks companies I contacted would quote without it. 
 

As for the cost it does look horrendously high. Our site was similar to yours also requiring a 30m retaining wall and the total cost was £67k which included a treatment plant, drainage field and rainwater attenuation. 

[saveasteading]

8 minutes ago, Kelvin said:

several quotes but you also need your full SE foundation design

You are asking for quotes to get a feeling for the cost, as they can't give firm quotes without a design. Thus these are guesses, some high maybe some low.

There may be a bigger contractor with the experience to estimate this fairly accurately. They might spare it  a couple of hours to do this, but it would still only be a guide not a firm offer.

Also please note: word will get round that you are asking multiple contractors. Only one can get the job and a proper quote costs them time and money. Just go to 3 or 4. 

Assume somewhere in the middle for now, but get it designed. 

[nod]

As above 

At the moment They are thinking of a number and doubling it Worse case scenario 

GW companies can easily loose money 

Muck away can cost a small fortune 

At least with a foundation design You can be pretty accurate with what needs to come out and what needs to go back in 

[AjitSingh213]

Hi All, 

 

Thank you so much for your responses, as you can imagine, extremely stressful time for us, which we expected with self building but maybe not so much before we had even started on site? Trying to remain positive about this and looking for a solution.

 

@Kelvin We have approached some other groundworkers who are more local, the ones that quoted were about 1.5 hrs away and seem like a large outfit with high set up costs so hopefully a smaller groundworker will charge less. Good to know re. your costs, at this stage we would even be acceptable to paying £100k for the groundworks package.

 

@saveasteading Thanks for the advice, we have gone to 1 who is doing the groundworks right next door for another self builder so he is familiar with the site, hopefully that helps. Another who is an old friend and another who we know through a mutual contact - all local, I will see what they come back with and yes, we will provide them with the SE designs. We received them this morning so have sent that all across to them including all of the surveys we have had done. 

 

@nod Agreed, as stated, we have the designs now, personally I can't make heads or tails of whether it is going to be that expensive or not, would it be helpful to post some images of what has been designed here? Or is it just worth waiting for groundworkers to come back with more quotes and then see what they say. Whilst we are digging down, and we agree and accept that will come at an extra cost, we just didnt think it would be that much. 

 

Again, appreciate the responses

 

Thanks

[Kelvin]

Always helpful to post some images. Anonymise them first though as this site is publicly searchable. 
 

Groundswork is the least predictable part of the build. You don’t know exactly what you have until the machines start excavating. Local companies are great to use though as they are more familiar with the ground. Also don’t be lulled into the mindset that £100k is good because you’ve already had a very high quote. As @nod said muck away is dear. We were lucky as we had somewhere to put ours so we didn’t remove anything from the site. 

[saveasteading]

2 hours ago, Kelvin said:

muck away is dear.

Minimise it. There are sometimes options on how to build that can save on muck away and replacing with concretd/ gravel etc.

[AjitSingh213]

Thanks @Kelvin I agree, we were aware about groundworks being unknown and are hoping that the ground investigation has given us a good idea of what is underground although understand we may still dig something up. Understood re. price, will stay optimistic that some of the smaller local groundworkers can give us a more appealing price. What foundation system did you use for your build by the way out of interest?

 

Thanks @saveasteading I will keep this in mind and speak to groundworkers about any value engineering that might be available. Our retaining wall is a cantilevered solid concrete wall for example but it isn't that high so have had some indications that there may be other options, along with alternative options for the foundation such as beam and block as opposed to insulated raft passive slab which may be more cost effective? But unclear on whether it will be as I understand that it is dependent on ground conditions? As far as I am aware, the ground investigation company said that the ground conditions were relatively good so hoping that there might be other avenues that we can take. 

[Kelvin]

Standard trench using insulated foundation blocks with insulation on outside and inside upstand and concrete slab. 

[Mr Punter]

I think the retaining walls faced with reclaimed stone are messing you up.  Get a proper design for the wall.  Get someone else to do the stone facings.

 

[Kelvin]

Our retaining wall is just built with concrete blocks and no facings or cladding. I quite like it. Looks rustic (ok unfinished) but it’s not the eyesore I thought it might be. We were going to clad it to match the house but have changed our mind. If we do finish it, it will be in facing stone. I’ll probably do that myself though. 

[AjitSingh213]

Thanks all, retaining wall alone is costing £37k I think, which is for a concrete poured cantilevered wall. It will likely look nice but not sure I can afford that! I will get some more quotes from local ground workers and maybe report back once I have some more clarity  

[saveasteading]

1 hour ago, AjitSingh213 said:

a concrete poured cantilevered wall

That is very specialist. A masonry wall should be half the price.

[AjitSingh213]

I hope so! I will double check everything and get a groundworker to have a look again at other options. I need to look at what strength of wall we need as the land behind will have cars driving over it as it is a driveway for the house behind.