ᐅ Reinforcement for Basement Slab

Hello,

I received the following quote from my basement contractor:

"For the 25cm (10 inches) thick slab with a double layer of reinforcement using Q 424 mats, the following costs will apply.

Approximately 20 reinforcement mats are needed in the basement slab. The weight difference between a Q188 mat and a Q424 mat is about 42.7 kg (94 lbs) per mat, resulting in an additional steel amount of a total of 854 kg (1882 lbs).

Extra steel in the slab = 854 kg (1882 lbs) * €2.00/kg = €1708.00
Extra concrete (increasing thickness from 20cm (8 inches) to 25cm (10 inches)) = 88.95 m² (957 ft²) * 0.05 m (2 inches) = 4.45 m³ (157 ft³) * €188/m³ = €836.60

This adds up to a total of €2544.60 for the desired basement slab specification."

Unfortunately, I have no experience in this area. Is this a reasonable offer? Or should I stick with the 20 cm (8 inches) slab without extra cost?

->>> There is slate underneath the slab :-(

It would be helpful if you had someone knowledgeable... the amounts you’re spending here, or not spending, certainly justify that.
The structural engineering should determine what needs to be installed, shouldn’t it?

Thank you for your help, but it doesn’t really assist me. The data comes from the basement builder, who will only commission the structural analysis once I have decided which foundation slab I want.

The structural engineering of the basement must be coordinated with the rest of your house, right, or are you only building a basement? I’m a bit confused.
Who is coordinating the different trades? What has been approved?

The foundation slab/basement is provided by the builder, as is the case, for example, with Heinz von Heiden.

You are putting the cart before the horse.

A structural engineer must tell you, based on the knowledge of the soil conditions and the construction project, what thickness and reinforcement you need.

Doing it the other way around makes no sense at all.