ᐅ Pouring a slab foundation (4x4 m) yourself: Is a concrete mixer suitable?
Created on: 27 May 2021 11:26
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MaxMustaman92
Hello,
I want to create a concrete slab foundation with dimensions of 4m x 4m x 20cm (13ft x 13ft x 8 inches). In about one month, a small garden shed made of 175cm (69 inches) calcium silicate bricks will be built on top, which should later be used to store tools and equipment with heavy weight.
The planned layers beneath the slab foundation from top to bottom are: PE foil, insulation, and a compacted gravel layer. The total depth of all these layers is 60cm (24 inches), plus the 20cm (8 inches) slab foundation. The surrounding strip footing (frost protection) is planned to be 30cm (12 inches) wide and 90cm (35 inches) deep.
This results in approximately 3.2 cubic meters (113 cubic feet) of concrete needed, which I plan to mix myself in a ratio of 1:4 (480kg cement: 1920kg gravel + 240 liters water).
Questions:
1. Is a concrete mixer still suitable for this amount, or should I hire a company to deliver ready-mix concrete? I would prefer to avoid the latter due to cost reasons if possible.
2. Are there any other recommendations or tips for carrying out my project?
I want to create a concrete slab foundation with dimensions of 4m x 4m x 20cm (13ft x 13ft x 8 inches). In about one month, a small garden shed made of 175cm (69 inches) calcium silicate bricks will be built on top, which should later be used to store tools and equipment with heavy weight.
The planned layers beneath the slab foundation from top to bottom are: PE foil, insulation, and a compacted gravel layer. The total depth of all these layers is 60cm (24 inches), plus the 20cm (8 inches) slab foundation. The surrounding strip footing (frost protection) is planned to be 30cm (12 inches) wide and 90cm (35 inches) deep.
This results in approximately 3.2 cubic meters (113 cubic feet) of concrete needed, which I plan to mix myself in a ratio of 1:4 (480kg cement: 1920kg gravel + 240 liters water).
Questions:
1. Is a concrete mixer still suitable for this amount, or should I hire a company to deliver ready-mix concrete? I would prefer to avoid the latter due to cost reasons if possible.
2. Are there any other recommendations or tips for carrying out my project?
H
HilfeHilfe28 May 2021 05:54MaxMustaman92 schrieb:
Hello,
first of all, thank you for all the replies.
What would be a good, cost-effective alternative if I want to build a 4x4 storage shed made of aerated concrete blocks (Ytong) or sand-lime bricks, where heavy items will sometimes be stored on the floor for extended periods (especially heavy building materials like stacked tiles and roof shingles)? Is there an alternative to a concrete foundation if the shed floor needs to easily support about 150 to 200 kg/m² (31 to 41 lbs/ft²)? As I said, simply compact the ground with gravel and place small strip footings on top. You can mix this as well. I don’t see the need for 20 cm (8 inches) of concrete.
G
Gartenfreund28 May 2021 06:40I would only use a strip foundation and create the ground surface with simple paving slabs. Whether the subsoil needs to be special is up to you. I can only say that here on site, I would simply level the ground with some sand and then lay the slabs directly on top. Then, work some sand into the joints and you’re done.
Any future dismantling will also be much easier than if a thick concrete slab had to be removed and disposed of.
Any future dismantling will also be much easier than if a thick concrete slab had to be removed and disposed of.
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MaxMustaman9228 May 2021 07:17Okay. So just excavate the soil about 30cm (12 inches) deep, then compact a 15-20cm (6-8 inches) layer of gravel and lay paving slabs on top? Is that enough for frost protection and to prevent moisture rising from the ground?
And should the strip foundation still be 80cm (31 inches) deep, or would that depth be excessive for a small shed? I mainly considered the depth of the strip foundation plus the 20cm (8 inches) concrete slab because I read that this is the minimum standard for protection against ground frost and moisture.
You’ve already helped me a lot so far, thanks!
And should the strip foundation still be 80cm (31 inches) deep, or would that depth be excessive for a small shed? I mainly considered the depth of the strip foundation plus the 20cm (8 inches) concrete slab because I read that this is the minimum standard for protection against ground frost and moisture.
You’ve already helped me a lot so far, thanks!
H
hanghaus200028 May 2021 07:17You don’t need 90cm (35 inches) deep foundations. A 7cm (3 inches) screed is sufficient. What is the insulation for? A timber frame construction is enough even for a shed.
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MaxMustaman9228 May 2021 08:24The choice of a stone wall (insulation) is based on the fact that the garden shed should remain low-maintenance for the coming decades (for example, without the need for painting and without rot-prone wooden components) AND I expect this to provide better protection for the stored contents (building materials, tiles, possibly also expensive metal tools). Therefore, I want to take measures now, while I still can, to minimize moisture buildup inside the shed and prevent damage to the contents.
MaxMustaman92 schrieb:
Ok. So just excavate the soil about 30cm (12 inches) deep, then compact a 15–20cm (6–8 inches) layer of gravel and place paving slabs on top? Hello
I have the exact opposite opinion. My motto is: more is better.
I recently completed a similar project: a motorcycle garage, 450 x 250 cm (15 x 8 feet).
I excavated an 80cm (31.5 inches) strip footing and removed the entire ground 60 cm (24 inches) deep. Filled up with recycled crushed limestone (RCL) to about 30 cm (12 inches). Laid paving slabs I had on hand (they provide a great clean layer), added plenty of reinforcement steel, then poured concrete. About 4 cubic meters (140 cubic feet) in total. With two friends, it was a good half day of solid work. A few sandwiches, plenty of malt beer. Now the slab is about 25 cm (10 inches) thick. It will hold.
And the payback: I help my two friends equally with their projects.
Steven
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