zoothorn

Basework on slope/ cabin.

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Hi all- my 1st thread. My lower garden is narrow 15m with a tricky ~45* slope, down to a stream: a near unuseable area due to profile. My plan to best use it, is to put a 3.5x3.5m log cabin 'across' it, making best use of area & 'covering over' the slope visually.

 

The left side/ easy surely.. but the right side's slope away is the issue, to create support for a base ontop up from here.

 

My builder had 2 ideas (& a hefty quote not inc a base optop- £900). Idea1: exacvate & "shutter 4 300x300mm concrete columns, 2 shallow, 2 deep stream side". Idea2: excavate, nip/ pull one side across, to a barrier (posts/ stacked gravel boards?)/ filling up this side.. to create a level patch.

 

So 4 coners 'pillars' idea? My concern is as ground is not the most stable on slope side, wouldn't a block maybe 'shift' over time pulling the base down & sideways? My concern with Idea2 is the pressure/ weight against the boards, & the new levelled ground 'settling/ sinking a bit over time, with concrete base on > cabin ontop of.

 

Any other ideas? a pic of the lower end, looking to where the front of cabin would be (2nd pic reverse view). Thanks zH

 

 

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That is quite similar to our burn.

 

Thoughts, in no particular order.

 

Don't build too close. The area under the cabin will be dry and will get no sunlight = no vegatation will grow = dry bare ground that will wash away easilly in flood (assumint like outs it sometimes floods)

 

Piles of some sort are what you want. A neigbhour here built a complete house on ground like this. They hd to dig quite deep to get to firm soil, removing a lot of soft top soil in the process. Then big square concrete pads. They built up from those concrete pillars using large plastic drainage pipe as formers.

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Or like Dave above with pads but steel pillars bolted to pads.

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Screw or helical piles may well be a good option, quick to put in, no concrete needed and are load bearing as soon as they are in.  We looked at them for the first plot we tried to buy (coincidentally also in Wales, just, in the Wye valley) and I was pretty impressed with what I found out about them, particularly that there were screw piles still supporting some seaside piers that were over 100 years old and still fine.

 

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Not dissimilar to my own build, although a more extreme slope.

I went with individual concrete pillars, different heights to create a level support structure.

Each pillar was made by digging out an approximately 800x800 hole down to firm ground, then pouring this up to ground level with rebar to tie it into the next pour. The second pour was a 450x450 shuttered column. I cast a 20mm diameter threaded rod into each column, and this holds down the building.

My build was made using a hefty Douglas Fir ring beam as a sort of 'chassis' upon which the floor and frame are built.

 

Of course for a small and lightweight structure this could all be overkill. You might get away with big strainer type posts set into the ground, especially if the cabin going on top is a strong monolithic box.

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7 minutes ago, Russell griffiths said:

 

 

 Was not to sure about that when he started, but looked pretty solid at the end. 

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^^ I expected him to stagger off and fall over at the end, like on YBF.

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Google "shed on slope". Lots of ideas there under Images.

Edited by Onoff

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Hi chaps- terrific helps thanks (just seen I got these replies!). 'Shed on slope'.. some things are so obvious eh? I'll look into that.

11 hours ago, Russell griffiths said:

 

 

 

Interesting ^.. certainly feasable as 2 for the easy side.. but I'm talking maybe a 3/4m height gap on the RHS: Id need something similar, but 3x as heavy duty/ tall to go deep, as ground here isn't so solid. The stream nearby compromising the ground in the adjacent area.

 

Do you think my quote of £900 (that's not even including anything above the 4 concrete blocks, not even pillar things prior to a base).. is OTT?

 

Appreciated, zootH

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18 hours ago, ProDave said:

That is quite similar to our burn.

 

Thoughts, in no particular order.

 

Don't build too close. The area under the cabin will be dry and will get no sunlight = no vegatation will grow = dry bare ground that will wash away easilly in flood (assumint like outs it sometimes floods)

 

Piles of some sort are what you want. A neigbhour here built a complete house on ground like this. They hd to dig quite deep to get to firm soil, removing a lot of soft top soil in the process. Then big square concrete pads. They built up from those concrete pillars using large plastic drainage pipe as formers.

 

Hi Dave- are the 'piles' (I only know the other type..) you refer to, effectively what my builder refers to in idea1? When you say don'y build too close.. you mean to stream, not house I guess?

 

can someone explain what 'shutter' means?

 

Does this idea3 have legs: re-use an old telegragh pole, do the concrete block idea with a 2m section of pole set in the middle. Top of it cut off at precise H > big notch for a solid timber beam to slot into. Any thoughts on this? Ideally this tricky side Id want something I could adjust for height, should there be any 'creep' over time wouldn't I?

 

Appreciated, zoot

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Piles, in building terms, are long posts made of precast concrete, steel, or wood, driven into the ground until they can support a determined loading. Generally used on larger projects like bridges, and where there is a deep layer of soft ground.

 

A shutter is a mould that you pour concrete into. Can be wood, plastic, metal, or even cardboard tubes. 

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Ok so in order to dig a hole for a shutter, in my eg/ 4 support points for a 500kg max log cabin/ fancyshed.. does it A) have to be done with a mini digger, B) have to go down to hit 'solid' ground, & C) would a mini digger of 1 ton bugger up going across my new lawn?

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How about a nice cantilevered shed with NO SUPPORTS?

 

Glass box overlooking the stream. All very GD!

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Just now, zoothorn said:

what is a cantilevered shed?

 

Magic ?.

 

i think you could dig it by hand, depends on your ground but 800mm to 1m should be deep enough, and big enough to Weald a shovel ! But only needs to be 300 to 400mm square ( at the bottom) a minidigger would be easier (costly) and if you bought some shutter ply for the lawn as protection it will not show much. You may have a problem operating a digger on that sloping site ( they can fall over !).

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10 minutes ago, zoothorn said:

Ok so in order to dig a hole for a shutter, in my eg/ 4 support points for a 500kg max log cabin/ fancyshed.. does it A) have to be done with a mini digger, B) have to go down to hit 'solid' ground, & C) would a mini digger of 1 ton bugger up going across my new lawn?

 

I wouldn't bother with the mini digger. In fact I dug my holes by hand. Yes you need to go down until you hit something firm- biggest problem is likely to be water from the steam seeping into the hole.

 

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Its soft ground.. but if you look at my 2nd pic, the hole would need to be twds very edge of the 'step'/ where the wonky post is on edge of.

 

How coukld a hole be dug here without the side collapsing?

 

I thought of those mini digger probs too.

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9 minutes ago, zoothorn said:

what is a cantilevered shed?

Like a cantilevered anything. Something supported via a beam sticking out sideways. IMHO you'll probably find that puts too much weight on the top of the slope at the edge, causing it to sink/collapse. Almost certainly not a practical solution unless the majority of the shed's weight is not going to overhang.

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Here's a left field idea. Make a sort of raft/palette from treated wood, that sits on the ground following the angle of the slope. Anchor it wherever possible by stakes, ratchet straps to convenient trees, etc etc. Then fix legs into it, cut for angle and length to create the level support needed for the shed.

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What I'd have thought best.. in theory.. is surely if these 2 supports could be A) as thin as possible to minimise any hole collapse & rule out as much excavation as possible, & B) deep enough to mitigate against instability. I'm thinking.. again in theory.. of the steel twisty post things/ but bigger/4x as high/ pro done, & somehow tethered to the bank side.

 

Does this idea4 have legs?

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4 minutes ago, zoothorn said:

How coukld a hole be dug here without the side collapsing?

 

Depends on your ground conditions, get a spade and dig a bit out, get through the topsoil (300 400 mm) and see what you got underneath, only then can you decide what to do. I think ground screws would be fine as Jeremy says, they just need to go down till they feel firm.

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I'll look into the ground screws idea.. have a feeling these are bang-up-to-date solution jobbies.. may just be the ticket, and, may not be in my 64yr old builders' knowledge if so recent a design.

 

But how, should either still shift even a wee bit over time, could I 'jack up' these do-da's?

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Ground screws would be cheap and simple. Other option is a post hole borer and fill with concrete as you go. Mix it with quick set and then just add some rebar to the top to tie in the “pretty” bits ... upturned buckets with the bottom cut out make good formwork for piers too. 

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Hi PeterW.. please explain a Rebar? hole borer > concrete fill.. along with groundscrew ideas: make SO much more sense to me. But who am I, a total novice, though to question my builders' innitial ideas1&2? I need help on how to put any new ideas to him w'out seeming like I'm a sniffy royal pita.

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