ᐅ Bill of quantities for shell construction and site supervision of the shell structure

Hello everyone,

I have a question. At the moment, I have only commissioned our architect for design phases 1 to 4.
Now I have asked him if he can prepare the bill of quantities (BOQ) for the shell construction and also carry out the site supervision during this phase.
He would prefer to charge for this on an hourly basis rather than a fixed price.
So, my question is: how long does it usually take an architect to prepare a BOQ for a single-family house? Can anyone give a rough estimate?

Additionally, it would be helpful to know how often the architect should be on site for shell construction supervision.
I want to roughly calculate the potential costs for these two services in advance.

The entire project has also been visualized in 3D, which I think will be a great help in determining quantities for the BOQ.

Thanks