ᐅ Foundation slab, plinth height, surveying

Created on: 24 Dec 2021 08:39
K
Kalibri
Hello everyone,

I hope this is the right forum for my issue; if not, please move it.

We are building a prefabricated timber frame house on a concrete slab. Initially, it was agreed that the house would be positioned 15cm (6 inches) above ground level, with a gravel bed as splash protection.

Now, the architects’ plans have been technically reviewed, with comments regarding the plinth height.

From my non-professional perspective, the plan does not seem to match this. According to the site plan, the finished floor level is only 13 cm (5 inches) above the pedestrian walkway. The top edge of the concrete slab appears to be level with the surrounding ground.

It seems there is a discrepancy. The architect refers to the 15 cm (6 inches) specification having been communicated to the construction company.

But then, doesn’t that mean all the height dimensions on the building plan are incorrect?

I might be wrong, but in my opinion, the plans need to be corrected. To ensure a slight slope away from the house, I would need a trench between the house and the pedestrian path.

Our architect does not seem willing to properly address this.

If the house is built according to the current plan, I believe we would have to install a significantly more complex recessed splash guard around the house, which is not what we want.

Am I missing something? Is my assessment wrong?
Hangman26 Dec 2021 15:08
Merry Christmas to start with 🙂

This is about timber frame construction, and here the floor structure itself is initially irrelevant. The focus is on the lower (wooden) sill of the exterior wall, which rests on the foundation slab and must be protected from moisture. Therefore, figure 14 showing the intended condition is correct (top of foundation slab = ground level + 15cm (6 inches)). I also suspect there is some confusion between the finished floor level and the top of the foundation slab (top of foundation slab). In short, the house really needs to be raised by 15cm (6 inches).

As a result, this means you will have approximately 31cm (12 inches) of space between the ground and finished floor level, so an entrance platform or similar will be necessary.
Nida35a26 Dec 2021 21:56
Our goal was to have everything level, so that the robotic lawn mower could drive straight into the living room, in this solid construction house.
In reality, the finished floor level (FFL) was about 60cm (24 inches) above ground level.
After adding fill to the paths and garden to create the necessary slopes, we ended up with a step into the house—very reassuring during heavy rain.
The step is located at the entrance and from the terrace down into the garden.
11ant27 Dec 2021 00:16
Nida35a schrieb:

Our preference was for everything to be level, so the robotic lawn mower can even go into the living room, solid house.
Could this setup actually encourage pairing a lawn mower robot with a vacuum robot? *LOL*
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
Tolentino27 Dec 2021 08:49
Not such a bad idea, actually.
Such a hybrid could also vacuum leaves in the garden and shred toys left out in the house. As a disciplinary measure for the kids...
K
Kalibri
27 Dec 2021 13:19
We have now spoken with our architect. He will raise the foundation slab by 15cm (6 inches).

He said that since there are no height specifications in the development plan, no changes to the building permit / planning permission are necessary. The application has already been submitted.

Is that correct? Or are we just taking a risk with this?
11ant27 Dec 2021 13:33
Kalibri schrieb:

We have now spoken with our architect. He will raise the foundation slab by 15cm (6 inches).

Did he also mention with what? – By the way, “raise” is only the correct term if the slab is already in place.
Kalibri schrieb:

He said that since there are no height specifications in the development plan, no changes to the building permit / planning permission would be necessary. [...] Is that right? Or are we taking a “leap of faith” here?

The latter. The development plan might not include a limit (which I haven’t checked), but the architect’s plan does. This is a document submitted with the building permit / planning permission. I would submit a revision in that case, or at least get a liability waiver from him.
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/