thanks for your patience, new at this and just working stuff out. 

 

I’ve crudely measured our site at around 5* or 10%. So for every 10m it reduces by 1m. 
 

is this within bounds for passive raft insulated foundation of about 75m2 (10x7.5m) 

Obviously with excavation and sub base layer and formation of some sort of retaining wall. 
 

If ground conditions ok, would this in theory support block inner and stone outer leaf? 
 

2 storey pitched roof

 

thanks 

Using google earth, height difference between top and bottom of site it’s actually 7* if that makes a significant difference. 

Our site slopes a similar amount and I discounted a passive slab for this reason.

 

No problem at the high end, but what do you do at the low end?

 

By the time you have excavated all the organic soft top soil, at least a metre here and then built it all back up with infil, then keep on building it up until you get to your slab level you are almost 2M of built up infil.  That would have been an awful lot of material to buy and compact in layers.

 

Then you would have to continue that raised infill beyond the house and either then slope it down to the ground level, or build a retaining wall.

 

It was oh so much simpler to do stepped strip foundations and then a well insulated suspended floor.  Less work, less cost, still a well insulated floor and nothing fancy to do with the garden levels.

Hi I have put a raft foundation in 5.5m x 12.5 m dug down 2m one end to level up sight removed 28 truck loads. So as long as the ground is good when you dig out it should not be a problem but raft needs to be on a flat level  ground

Keith

1 hour ago, goatcarrot said:

...

is this within bounds for passive raft insulated foundation of about 75m2 (10x7.5m) 

...

 

Yes.Ours slope is at least 2 meters (more often more) across the site (25 meters) . The fence behind the 14 tonner is 2 meters high.

The raft has 64 piles underneath it (£6500) because we are on Made Ground .  Piling took one day, everything finished in 3.

 

This photo shows the fall across the site.

Edited March 10, 20215 yr by ToughButterCup

@ProDave  I can see your logic there. 

so re the stepped strip foundations would then have beam and block suspended floor with insulation on top and then screed/ufh?
 

or I could have a stepped floor level perhaps if staying with the raft? 

@keith65  I see so you’ve gone longer and narrower. How many bedrooms and what’s your layout? Are those up stands for ICF? 

@ToughButterCup thanks, ours is a big field with usually good conditions so we have space to get the muck away and even out the levels elsewhere avoiding trucking it out. 
quarry up the road does crushed stone for £15/ton delivered, maybe cheaper in bulk

What attracts me about the raft apart from the simplicity is that I can potentially do most of it myself if it’s mainly just digging and moving stuff about. 
 

the stepped strip footings I can’t really envisage in my mind’s eye yet

1 hour ago, goatcarrot said:

What attracts me about the raft apart from the simplicity is that I can potentially do most of it myself if it’s mainly just digging and moving stuff about. 
 

the stepped strip footings I can’t really envisage in my mind’s eye yet

I dug the footings myself with my own little digger, then the builders poured the concrete and built up from there.  Timber suspended floor.

 

 

 

In the above picture the FFL is only just above ground level, but at the far left corner is over 1M above ground level.

@ProDave interesting thank you

 

if using strip footings with beam and block is it a similar approach but with the insulation on top? Is it then possible to achieve ph levels of insulation and thermal bridging do you know? 
I’m trying to look at alternatives to wood in the substructure 

Hi 

Mine is a one bed house with double garage so house is only 7.25m x 5.5m  two story in Isotex icf

Thanks for the replies. 
 

I really like the raft idea however what about rodents nibbling away at the EPS , is that not a risk factor? 

No.

Cover it with lead,  or in our case lead replacement. ( forgotten the trade name)

Ubiflex B3 Lead Alternative Flashing 250mm x 12m (3.5mm Thick) - Black

1 hour ago, ToughButterCup said:

Ubiflex B3 Lead Alternative Flashing 250mm x 12m (3.5mm Thick) - Black

 

This seems to be for the usage above the ground only? Lifetime of 30 years worries me a bit. 

Ok so that would sort the edges but what’s to stop them burrowing up from underneath I wonder. Can’t be nice chewing eps if you’re a rat I guess but I’ve seen evidence of it in an old caravan! 

5 minutes ago, oldkettle said:

 

This seems to be for the usage above the ground only? Lifetime of 30 years worries me a bit. 

 

It may worry you, lad ?. But I'll be dead or so out of it that I won't care by then

 

4 minutes ago, goatcarrot said:

... what’s to stop them burrowing up from underneath I wonder...

 

Nothing.

I too am considering using Ubbiflex B3 for covering my insulation at the bottom. I have the samples of grey and black (tempted by the black).

 

I am puzzling over fixings. @ToughButterCup, how did you attach yours to your EPS?  

 

Regarding stopping vermin, I am thinking of putting a narrow layer of MOT-style stone right next to the house and up against the Ubbiflex. I assume the buggers won't chew or burrow through stone. Then backfill with soil for my flower beds.

Edited March 12, 20215 yr by Dreadnaught

2 hours ago, oldkettle said:

Lifetime of 30 years worries me a bit. 

 

Suspect that's a minimum. Or rather a maximum that their lifetime-aging-system will allow them to estimate. 

30-years will see me out. And it will probably be an easy-ish job to replace it when the times comes.

Edited March 12, 20215 yr by Dreadnaught