It's getting serious now....

[Alan]

Hi guys, although I've been a member for a while now there's been no need for me to have any input....until now!

First of all...what a fantastic forum! Although I can't pretend to understand a lot of it, I feel I've learned a huge amount which has definitely helped give me the confidence to continue and build our dream house. Someone famous once said 'I know enough to know I know nothing' or some variation of that....I guess that's where I am currently!

We've been planning this for many years and doing all the niceties, going to the build shows, reading the glossy mags, drawing up our plans and then re-drawing and re-drawing....over the years we must have made at least 20 versions before getting the Architect involved. We have no previous experience but plan to demolish our existing property and erect a new build. New build will have an ICF Basement with Ground and First floors Timber Frame. We've had our Topo and Eco Survey done although we are awaiting a further Bat Survey in May (money for old rope).

I will be attending some ICF courses in the coming months before making a final decision on provider with a view to going to planning in the summer.

I've read on here that there's no such thing as a 'stupid question'....I will certainly be putting that theory to the test so apologies in advance!

 

[Gone West]

Hi, welcome to the forum. It's a great resource as you've found. Good luck with your build.

[Mr Punter]

Hi @Alan and welcome.

 

Before your architect does their detail drawings, make 100% sure that your warranty provider and building control are happy with an ICF basement.

[ragg987]

Best of luck and ask away. We built an ICF basement (Integra-Spec ICF and Kryton waterproofing admixture) with MBC timber-frame double story on top, very happy with the result 3 years in.

1 hour ago, Mr Punter said:

Before your architect does their detail drawings, make 100% sure that your warranty provider and building control are happy with an ICF basement.

Good point. For warranty we did have some challenges, our install does not have separate tanking or drain channel and this became a discussion point, but we got the cover we wanted. BC did not raise any questions.

[Conor]

17 minutes ago, ragg987 said:

Best of luck and ask away. We built an ICF basement (Integra-Spec ICF and Kryton waterproofing admixture) with MBC timber-frame double story on top, very happy with the result 3 years in.

Good point. For warranty we did have some challenges, our install does not have separate tanking or drain channel and this became a discussion point, but we got the cover we wanted. BC did not raise any questions.

 

Who sorted your basement tanking guarantee? Have you a mortgage on the property?

[Bitpipe]

Just done a big basement post on another thread.

 

ICF with wp concrete (Kryten, Sika etc) is a great system, but the concrete placement needs to be bang on as you can't see any issues due to the insulation - did you do the ICF yourself or use a contractor?

 

Separate tanking should not be required depending on ground conditions but some warranty systems will ask for two out of the three systems (external, concrete and internal).

 

We got an all in warranty (Ark I think) but by the time we got BC sign off to release the policy, somewhere in the insurance chain had bust but we got an equivalent policy from the broker at no extra cost. Not that it's worth anything really but necessary if you wanted to mortgage or sell.

 

[Bitpipe]

3 hours ago, Alan said:

Hi guys, although I've been a member for a while now there's been no need for me to have any input....until now!

First of all...what a fantastic forum! Although I can't pretend to understand a lot of it, I feel I've learned a huge amount which has definitely helped give me the confidence to continue and build our dream house. Someone famous once said 'I know enough to know I know nothing' or some variation of that....I guess that's where I am currently!

We've been planning this for many years and doing all the niceties, going to the build shows, reading the glossy mags, drawing up our plans and then re-drawing and re-drawing....over the years we must have made at least 20 versions before getting the Architect involved. We have no previous experience but plan to demolish our existing property and erect a new build. New build will have an ICF Basement with Ground and First floors Timber Frame. We've had our Topo and Eco Survey done although we are awaiting a further Bat Survey in May (money for old rope).

I will be attending some ICF courses in the coming months before making a final decision on provider with a view to going to planning in the summer.

I've read on here that there's no such thing as a 'stupid question'....I will certainly be putting that theory to the test so apologies in advance!

 

 

If it helps, I built very similar to you (demolish, cast in situ basement vs ICF and 2.5 storey MBC TF passive standard house on top) with zero prior experience.

 

Could not have done it without this forum and its predecessor.

 

Ask all the 'stupid' questions you like

 

Have you done the ground investigation survey yet? This is the one that determines the spec & cost of the basement  (or any foundation structure).

Edited February 22, 2020 by Bitpipe

[Thorfun]

Welcome! I’m also a new member but have already asked a number of questions, read many blogs and learnt a lot, but I’ve still a lot to learn. I’m also looking at building a basement and the big basement post @Bitpipe mentioned was in response to a post of mine. Some great info and can be found here:

 

 

[Thorfun]

2 hours ago, Bitpipe said:

 

Have you done the ground investigation survey yet? This is the one that determines the spec & cost of the basement  (or any foundation structure).

my architect suggested waiting until we had planning permission before getting this survey. But I’m thinking we should get it now as even if planning is rejected the plot has permission for a new bungalow obtained by the previous owner so even if we build that we will need a geotechnical survey. So I can’t think of a reason not to get it done now. Assuming cash flow allows it of course! But welcome the thoughts of others. 

[ragg987]

2 hours ago, Conor said:

Who sorted your basement tanking guarantee? Have you a mortgage on the property?

Kryton provided the water tight guarantee. They included inspection during the build. Yes we have a mortgage, they did not ask any questions about basement.

[Alan]

2 hours ago, Bitpipe said:

 

If it helps, I built very similar to you (demolish, cast in situ basement vs ICF and 2.5 storey MBC TF passive standard house on top) with zero prior experience.

 

Could not have done it without this forum and its predecessor.

 

Ask all the 'stupid' questions you like

 

Have you done the ground investigation survey yet? This is the one that determines the spec & cost of the basement  (or any foundation structure).

We haven't done the Ground Investigation Survey yet. My focus at the moment is choosing the ICF so as to finalise our drawings. I'm going to try and 'size' the build around the block sizes of the ICF so as to cut down on wastage and cutting.

Do you think that the GIS should be done before choosing my ICF as the results might have an impact on what type of ICF to use?

[Bitpipe]

18 hours ago, Alan said:

We haven't done the Ground Investigation Survey yet. My focus at the moment is choosing the ICF so as to finalise our drawings. I'm going to try and 'size' the build around the block sizes of the ICF so as to cut down on wastage and cutting.

Do you think that the GIS should be done before choosing my ICF as the results might have an impact on what type of ICF to use?

 

Probably not - depends on the choice of wall thickness you have. Basement walls are usually 200mm-300mm thick depending on the SE's design, what kind of structure it is, what's on top etc. I'd guess that your ICF will have enough flexability in that respect.

 

We went for an 'open box' design so we could have flexibility of layout and a suspended timber floor to simplify the heating design. However that meant that the walls & slab needed to be thicker than usual (300mm) plus extra steel. We probably could have built a 200mm thick closed box for the same cost of concrete & steel and saved the cost of the suspended floor but the build cost would have been higher to construct the lid so it probably all netted out.

 

GIS fundamentally tells the SE the bearing strength and composition of the ground which usually dictates the design of the slab. To preserve the passive design of the house above, we put the slab on a layer of 300mm thick EPS 200 which extended beyond the walls by about 300mm to meet the 200mm thick EPS 70 vertical insulation. 

 

GIS also tells you the ground water levels which will dictate your waterproofing strategy and the overall site conditions will influence the build strategy (i.e. are you on solid rock, clay, chalk, gravel). Site conditions (and access, party wall considerations) will also influence overall cost as when you know what material you're excavating, you know how much it bulks up and what the cart away costs will be. From memory, Chalk is 3:1. clay 2:1 and gravel and rock about 1:1. While muck away trucks are rated to 20t, they can only be filled to a certain volume so this is important as you're usually charged per M3 for excavation, cart away and backfill.

 

The excavation design is also important - you usually can't just dig a straight sided hole as it may be unstable, so the sides are 'battered back' (dug at an angle) which generates more spoil - however this can be used to refill the battered portion if you backfill the usual 1m working gap between finished wall and ground with something free draining like clean stone. If you use site spoil to refill, it needs to be compacted every 200mm. Party wall also applies from the mouth of the excavation so if that's less than 6m from a neighbouring wall then you need to check the 45^o intersection rule to see if you're clear - if not you may need to resort to sheet piling.

 

I was away from site the final week of basement works and I suspect that  the contractor skimped on stone for the rear of the house as, while it all looked great when he left, about 6 months later there was significant settlement in that area and I needed to backfill it with a lot of type one when doing the landscaping - patio has still settled a touch which caused a few issues. I had retained a few £K for residuals so rather than get them back I never paid it and they never chased for it.