Atacama Yellow 35is build thread

[Zed Baron]

Are you installing a lift?

[B21]

Are you installing a lift?

I’m going to go with a moveable hydraulic scissor lift as per John-E89 suggestions..

Hopefully 8” of reinforced concrete can cope with the spot loads..

[Pondrew]

Interested to know why you did gabions as 'shoring', rather than building 4" concrete blockwork (maybe rendered then painted) walls, Peter?

Sad, I know, but concrete slabs and building floats my boat.

[Pondrew]

Hopefully 8” of reinforced concrete can cope with the spot loads..

It will. Maximum 500kg on each corner is a walk in the park. The re-inforcing mesh acts like coursing on brickwork; distributes the load pretty well.

[B21]

Interested to know why you did gabions as 'shoring', rather than building 4" concrete blockwork (maybe rendered then painted) walls, Peter?

Sad, I know, but concrete slabs and building floats my boat.

It’s low tech for a non professional building person like moi, I’ve used it elsewhere to hold back collapsing banks caused by too steep an angle bank cut out when they formed the building lots.. / an awful lot of subterranean water flowing down our hillside in winter..

AFAIK block work needs a good foundation and by dint of the location access to making a nice set of perimeter foundations were a bridge too far..

The rear wall is massively over engineered now….I knew the pad at 6” was rated for 3 tonne load but in B21 fashion you can’t beat excess engineering..

Well pleased with the results..

[B21]

Hopefully 8” of reinforced concrete can cope with the spot loads..

It will. Maximum 500kg on each corner is a walk in the park. The re-inforcing mesh acts like coursing on brickwork; distributes the load pretty well.

Just joshing ..laid many concrete pads for aircraft hangars in a previous life…

[Beeacon]

Interested to know why you did gabions as 'shoring', rather than building 4" concrete blockwork (maybe rendered then painted) walls, Peter?

Sad, I know, but concrete slabs and building floats my boat.

It’s low tech for a non professional building person like moi, I’ve used it elsewhere to hold back collapsing banks caused by too steep an angle bank cut out when they formed the building lots.. / an awful lot of subterranean water flowing down our hillside in winter..

AFAIK block work needs a good foundation and by dint of the location access to making a nice set of perimeter foundations were a bridge too far..

The rear wall is massively over engineered now….I knew the pad at 6” was rated for 3 tonne load but in B21 fashion you can’t beat excess engineering..

Well pleased with the results..

I would say that gabion walls are the better option here, as otherwise your block wall would need to underpin the bank and be backfilled. Also, the block wall would need reinforcing or piers adding to deal with the overturning moment induces by the active earth pressures.

Glad you're happy with the results.

Regarding the lift and 200thk slab, did you put some mesh reinforcement in the bottom of the slab where you were intending to put the vehicle lift supports? Your 200thk ground bearing slab should have your mesh in the top of the slab typically, and also a bit in the bottom local to the lift's supports as per my previous recommendation.

I don't think it would be the end of the world if you don't have rebar in the bottom of the slab, but you would end up getting a bit of local cracking that can be locally patched up if necessary in a few years time.

[john-e89]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

[B21]

Thanks for the considered opinion on gabions vs walls..with my skill set it was never going to be a wall....

Ref the pad..it averages 270mm in the end not 200mm and has mesh all over in two layers one at 50 mm above the stone and 50mm below the top level (all approx)

Not sure on the hydraulic mobile scissor jacks how the loads transfer to the concrete but with it being RC25-30 hopefully it will hold up?

[B21]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

John..all noted thanks ..your experience is re-assuring..I was going to put a bit of self levelling on the surface but will skip that..

[john-e89]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

John..all noted thanks ..your experience is re-assuring..I was going to put a bit of self levelling on the surface but will skip that..

Yep don't self level where the lift is going Peter, it'll definitely crack up, it's not designed for lifts etc.

[B21]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

John..all noted thanks ..your experience is re-assuring..I was going to put a bit of self levelling on the surface but will skip that..

Yep don't self level where the lift is going Peter, it'll definitely crack up, it's not designed for lifts etc.

Got it thnx..chap who is self building 2 doors up (professional builder) pointed out the likely outcome of that..

Although there a 5mm-7mm depression over a large area (realtive to the edges) which shows up in rain, once under cover I don't think you would ever see /realise it..

We used a very wet mixture as access was very limited so quite alot of water came out..hence the depression.

[Beeacon]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

It is not so much a question of what the thickness of the slab is, but more of the compaction of the fill underneath. If you end up developing some softspots underneath (as I don't imagine the earth under this would have warranted fill and compaction in layers) you can develop local cracking as you're asking the ground bearing slab to span further.

You're right in that if the footing is not a simple point load from a post but has a spreader plate, then this would obviously help.

Ref the pad..it averages 270mm in the end not 200mm and has mesh all over in two layers one at 50 mm above the stone and 50mm below the top level (all approx)

Regarding the reinforcement in top and bottom, that should do just lovely, it will likely be able to span over any softspots that develop, even if you have a single point load from the jack.

Not sure on the hydraulic mobile scissor jacks how the loads transfer to the concrete but with it being RC25-30 hopefully it will hold up?

I wouldn't worry too much on this front. If the granular fill under the slab is well compacted, then the concrete is effectively just passing the load through it. An RC25/30 mix (25 being 25N/mm² cylinder strength of the concrete under compression, 30N/mm² being the cube strength for all you nerds out there) will be fine, you'll never get near the crushing strength of the concrete, it will be down to localised tensile loads, which concrete is poor at, that will cause you headaches in the bottom of the slab. But as you're doubly reinforced the bottom reinforcement should deal with the tension for you.

Hope this helps,
Beeacon.

[Beeacon]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

John..all noted thanks ..your experience is re-assuring..I was going to put a bit of self levelling on the surface but will skip that..

You can get high strength screeds, but it will likely be a full screed laid to a minimum thickness of ~25mm, it wouldn't be self levelling though.

[B21]

Agree with Beeacon on the gabion walls, perfect solution imho.

The scissor lifts have a long footprint and thus spread the load very well. My previous rented workshop was barely 4inch thick with no mesh and I had no cracking around the lift, and that was a heavy 3ton capacity lift that is way too extreme for Peter's needs.

John..all noted thanks ..your experience is re-assuring..I was going to put a bit of self levelling on the surface but will skip that..

You can get high strength screeds, but it will likely be a full screed laid to a minimum thickness of ~25mm, it wouldn't be self levelling though.

All noted….frankly by my limited standards ‘/ expectations I’ll live with some minor deviation from perfection in terms of slab level…

I can’t see any deviations but water is a cruel exposer of any discrepancies..

I’ll just put a nice couple of coats off garage floor paint once the pad dries out…Leyland paints suggest one month of drying for every inch of concrete..

I’ve burnt my way through the best part of £4k just in materials and tool hire…