Concrete Subbase_log cabin

[brackers99]

I'm building a base for 4x3m log cabin (fancy shed) and intend to sit it on 75mm-100mm of concrete which will be poured into a form which is raised above hardcore using stakes.

The hardcore is old bricks & concrete which I have sledge-hammered down to about 5-7cm pieces. I want to put a DPM before the concrete, but need something that will be flat and level so I don't piece the DPM. I could use, MOT Type 1, ballast or sand and now have two questions:

1: How much extra MOT Type 1, ballast or sand to account for gaps in bricks? I can use an online calculator to work the amount, but a fair amount will sink into the cracks in the rubble and that is the difficult bit.

2: Do I need to hire a wacker/ vibrating plate? I do have an iron tamper bar.

Thanks

 

[noseall]

An area of 12m² at 100mm deep would take a couple of tonne of mot.

However as none of us are equipped with mind reading abilities, no one is going to know exactly how much needs filling or what depth is remaining.

Yes, you will need to compact the hard core as well as the sand blinding layer.

It's up to you how you compact it. A vibrating plate is the most efficient way usually.

 

[brackers99]

An area of 12m² at 100mm deep would take a couple of tonne of mot.

However as none of us are equipped with mind reading abilities, no one is going to know exactly how much needs filling or what depth is remaining.
My crystal ball is broken too . Hardcore depth is about 75-100mm leaving 25-50mm for the blinding.

 

[brackers99]

For the blinding layer, I am going to order 1 bulk bag of MOT with the intention of obtaining a 1 inch layer. This should use ~ half a bulk bag and I am going to guess about 1/2 bag will dissapear through all the brick gaps when I use the vibrating plate I am going to hire.

If I am wrong about guessing how much material for the blinding layer, I will either have a slightly thicker layer or have lots of waste. I know this is simple everyday stuff for a builder, but I have never done any concrete work before but wish to get stuck in as part of a diy project and keep my costs down.

Thanks

 

[noseall]

For the blinding layer, I am going to order 1 bulk bag of MOT with the intention of obtaining a 1 inch layer.

Your terminology is a little off.

The 'blinding' layer is a fine layer of non-granular material i.e. sand, that is laid over the coarser material in order to prevent puncturing the dpm.

However, you are wise to run a layer of mot over your broken bricks as this will indeed fill in any gaps and should compact reasonably flat. MOT is usually bagged using 30mm to dust, so you have the best of both worlds i.e. fine stuff and granular stuff.

Quantities are impossible to predict especially as you are adding to an irregular surface. Will you be wanting to lay a pathway or similar towards and around the building?

 

[brackers99]

Cheers for pointing out my error of thinking the MOT layer could be a blinding layer. Glad you understood what I meant though.

I have ordered all the materials and will attack this next weekend. I have also hired a mixer and an 88kg wacker plate from HSS.
I like your idea about a path and I have a small tool shed that needs a base, so if there is any material left, I can make use of it.

Thanks for your help. Much appreciated.