Passive Slab on a slope or go Concrete free.

[Patrick]

I know this has been discussed at some point, but it was on a very tiny slope and I have found nothing about anyone trying near a Watercourse or similar.

So my question is:

 

Is it possible under any circumstances to build Passive Slab on a slope of ca. 1.5 meters next to a Watercourse.

My guess is "No"

But i still think it s worth a try, as this would be a good slab solution.

 

Here is some measurements (see Pic below) . House will be on a slope of 1.5 meters over 21 meters distance.

But the bigger problem probably is the Watercourse directly next to it - oh, and I forgot- a few trees as well.

I will ask Structural Engineer the same question, but her solution so far is not really a cheap one

(Pile and Beam with slab , first quote coming is : 47000£+VAT  ? ?)

Thinking by now that it might be best to leave concrete out and just put suspended Timber Floor on Screwpiles.

Anyone in here got experience with this?

Even Though Helical Piles are not cheap, might still end up much cheaper.

Has anyboday ever tried installing helical Piles themselves ? I just had a quote for the Piles themselves - just material - 1600mm length excl. shipping for 15USD each (100/pallet) , seems cheap enough to me ?

 

 

[ProDave]

Your site looks similar to mine, except my slope was less, and the trees and the stream a bit further away.

 

I considered a passive slab.  The big problem for me, was you have to build up the ground with crushed stone etc and that has to extend a bit beyond the house area. So it would have ended up having raised ground all around the house, then sloping down further out to the lower ground level.

 

In the end I did pretty normal strip foundations and a suspended insulated timber floor.  The foundations were specified by the structural engineer and the only things he did a bit different to normal were a reinforcing mesh in the concrete pour of the foundations, and a strong concrete mix specified.

 

A near neighbour to here built his house on a much more challenging small plot close to the burn and on a much steeper slope, he built his on piles. The builders dug down to pour a 1 metre square pad for each pile, then cast concrete piers using plastic drainage pipe as a former.  I don't know the cost but I suspect not cheap, largely because they had to remove a lot of soil, store it elsewhere, then bring most of it back (I would have asked the local farmer if we could rent the corner of a field to store it locally instead)

 

This is a picture of his piles before the house went on top:

 

[Patrick]

that looks good-like you said, sounds expensive though .

 

[Jeremy Harris]

We are 1.6m above a watercourse, on a slope that is pretty steep, on gault clay, and we have a passive slab, with no need for piles etc.  There's stuff about our passive slab in a few entries of our blog (earlier entries than this show the ground works needed to get the site level): 

 

http://www.mayfly.eu/2013/08/part-ten-out-of-the-ground/

 

http://www.mayfly.eu/2013/10/part-sixteen-fun-and-games-in-the-mud/

 

 

[PeterW]

Could build a retaining wall of gabions down toward the watercourse and then backfill for the slab - won’t go anywhere and it’s used fairly widely as a retaining section. 

[Patrick]

6 minutes ago, PeterW said:

Could build a retaining wall of gabions down toward the watercourse and then backfill for the slab - won’t go anywhere and it’s used fairly widely as a retaining section. 

That would be a great option,  it is a bit similar then @JSHarrisdone it with his Wall in order to get the plot level.

I think the small problem I have got is space- there is around 0.5-1 meter between the building and the Watercourse and there is a drop of around 0.8-1.2 meters .

Would be obviously better to build a bit further away, but thats also not possible.

I do however follow up on some advice and get Guys from MSS `mini`soil surveys in to give me advice with how to proceed . He has been recommended more then once on here .

 

[PeterW]

Is that a moving water course or a lake ..?? If it’s moving you will need to go with piles or similar as you will need to ensure the water can’t erode the bank. I’d be inclined to use shuttering piles to create the retaining wall and put the slab on top and you can go pretty much to the waters edge. 

[Patrick]

16 minutes ago, PeterW said:

Is that a moving water course or a lake ..?? If it’s moving you will need to go with piles or similar as you will need to ensure the water can’t erode the bank. I’d be inclined to use shuttering piles to create the retaining wall and put the slab on top and you can go pretty much to the waters edge. 

it s moving water, even though very small ( it s a little stream , around 0.5meters wide, 0.3m deep max.) . Good Idea , I will look into this

[ProDave]

1 hour ago, Patrick said:

it s moving water, even though very small ( it s a little stream , around 0.5meters wide, 0.3m deep max.) . Good Idea , I will look into this

So is our burn most of the time, but boy it knows all about spate from time to time.