ᐅ Extension of a detached single-family house by adding an additional floor

We plan to add an additional storey to our house through one of three construction companies in our residential area.
+ How many months in advance should the initial planning meetings take place?
+ What should we pay special attention to?
+ How many months before should cost estimates be obtained if at least 60% of the financing is secured through equity and the rest as a loan from the house bank?
+ When should windows and balcony doors be ordered?

+ Is a rough estimate of €1500 to 1700 per m2 (approximately $160 to $180 per sq ft) sufficient for masonry, one ceiling/floor slab, seven windows, two doors, the roof truss, and roofing with a simple finish?

Pellet heating, chimneys, solar panels, and the staircase are already installed.

Looking forward to your answers and best regards.

Start discussions as early as possible because if you begin too late, you become inflexible and are under time pressure.

For such a project, a building permit (planning permission) is required. This means an architect and a structural engineer need to be involved. However, a construction company may already have these professionals on their team.

Thank you for the response, but perhaps someone can provide more detailed and specific answers to my questions.
I am simply unclear about the timeline.
Greetings from Austria

Contrary to the questions asked, I would first clarify whether the project is 1) structurally feasible and 2) allowed according to planning regulations. I am quite skeptical about both. A one-and-a-half-story building is usually not designed to support an entire additional full floor. Regarding point 2), you should initially check the setback requirements and, if necessary, review the zoning plan or building permit conditions.

If point 2) does not pose a problem, then the further approach depends on point 1), namely possible construction methods and any required structural modifications. The costs can vary widely, especially with a project like this. There is a huge difference between adding an attic to a bungalow and converting a one-and-a-half-story building into a two-and-a-half-story building (which, to be honest, would make me consider selling and buying instead).

Hello,

Garten2 schrieb:

We want to add an additional floor to our house through one of three construction companies in our residential area.
+ How many months in advance should the initial planning discussions take place?
+ What should be particularly considered?
+ How many months in advance should cost estimates be obtained if financing is secured with at least 60% equity and the rest as a loan from the house bank?
+ When should windows and balcony doors be ordered?

+ Is a rough estimate of €1500 to 1700 per m2 (10 to 16 USD per sq.ft) sufficient for masonry, one ceiling, 7 windows, 2 doors, roof truss, and simple roofing?

Pellet heating, chimneys, solar panels, and staircases are already in place.

I understand that these questions are important to you, but unfortunately, you are putting the cart before the horse, or (almost) mentally moved in already.

Before you continue dreaming and calculating, a structural engineer must review the currently valid calculations of the single-family house. It is not necessarily the case that adding another floor is so easily possible; unless this was already considered during the original design of the house. It is often necessary—as is usually the case—that concrete pads are installed as supports on the ground floor. Probably, no concrete ceiling was built above the ground floor either?

So, step 1: consult a structural engineer with the current calculations; if possible, the same engineer who originally calculated the single-family house.
2. If it turns out the structure is load-bearing enough, hire an architect to create the designs.
3. If additional preparatory work is needed to ensure the load-bearing capacity for another floor, have the structural engineer perform the calculations first. Only then approach the architect to draft and plan.
4. You can never start financing discussions too early.
5. Once clarity is achieved—either way—ask the three construction companies for an offer based on the new drawings.

Three construction companies suggests that they will also handle the conversion work; then a tender (bidding) is not necessary. If you want to build through an architect and only have the construction companies deliver the shell (possibly installing additional supports on the ground floor), then the tender should start as soon as the building permit / planning permission has been submitted.

Please also remember—you mentioned that some components are already on site—that most contractors use mixed calculations; this applies to the two construction companies as well. This means their offers consist of materials, labor costs, and margin. So, if you want to supply some of the installations yourself, the labor costs and margin will likely compensate for this “loss in revenue.”

Regards, Bauexperte