Cost check foundation garden house 4x4

I had originally planned to set up our garden house on a continuous concrete slab and to do it myself. Upon closer planning, I realized that this is exactly the intermediate size that is no longer easy to do manually, but somehow too small to rent an excavator and have concrete delivered in a half-empty truck mixer. Therefore, I asked our general contractor what he would charge for a 4x4m concrete slab, and he quoted €2960 plus VAT, so just under €3500. Is that a usual price if you have it done? I would have expected about half of that.

The scope would be the complete package, i.e. preparing the area, frost-proof foundation, 25cm reinforced concrete slab. (A bit luxurious for a garden house, but I only specified 4x4 for a garden house)

I just completed something similar, made a foundation myself. Not for a garden shed but for a lifting platform. 3x4 meters. Material costs about €300, there were three of us and we took about 5 hours.

I have laid about 4 m² of foundation for walls and stairs here in the garden. It took a bit longer because of the shape and cost me 440 euros. For a simple base area, it takes no more than 3 days alone (one day for digging, one day for adding gravel, one day for concreting). Costs for self-construction should not exceed 800 euros by much (60 cm frost protection + 20 cm concrete foundation).

Do you have a concrete station or similar nearby? I had part of the concrete and all the gravel delivered in a big bag because I didn't feel like loading and mixing 40 bags of dry concrete at Hornbach again. And despite the 49 euro delivery fee, the price was about the same.

Asked the other way around: Why does your garden shed actually need a concrete slab at all? Do you have something special planned for it?

If not, isolated footings are completely sufficient. You can easily make those yourself.

Concrete slabs are material- and cost-intensive. And you don’t even want to calculate the CO2 for the concrete.

A different question: Why does your garden shed actually need a concrete slab? Do you have something special planned with it?

If I saw that correctly, a concrete slab is generally recommended for larger houses and on clay soil. Then you could also have saved yourself the floor.

My original considerations were something like this:
- with 3-4 cubic meters of concrete, you no longer want to mix it yourself due to the time involved, and the quantities of cement are already borderline for picking up at the hardware store (3 cbm -> 1.4 tons)
- having concrete delivered is annoying because of the small quantity surcharge for half-full truck mixers
- the earthworks for it are also somewhat at the limit to still do without a mini excavator
- same goes for the material for the substructure
- the general contractor would have an excavator anyway and has concrete delivered for the house, so just ask

Costs for self-construction should not be much more than 800 euros (60cm frost protection + 20cm concrete foundation).

Yes, that was also my estimate for the material costs, possibly some extra for the excavator. Since the general contractor has everything on site anyway and has no problem with small quantities, the expectation was that it would come out at about twice that.

Meanwhile, I’m also wondering if the simplest and cheapest solution wouldn’t be a foundation made of paving slabs in a frame of edging stones (I saw a good video from Hornbach about this). I still don’t have to make a final decision about what kind of foundation I’ll do; I only have to decide whether to have the GC do it when he pours the house’s concrete slab.

One consideration was also that if the concrete slab is already finished, I could already put up the garden shed this summer. Then you would already have a place for bicycles, etc., when moving in, and wouldn’t have to leave it standing in front of the house for half the winter. Although I have now considered that I might also be able to do the foundation this summer when the interior finishing workers are on site. The only question is when such a house actually has proper electricity and water...

If I saw that correctly, a slab foundation is generally recommended for larger houses and clay soil. You could then also have saved the floor.

Financially, the wooden floor is certainly much cheaper for you than even the material cost of the slab foundation. And recommendations on the internet are usually very general. Our entire residential building, for example, does not have a slab foundation ;-) It purely depends on your specific usage plans. What are they?