Finalizing Bids for Excavation and Structural Work

Almost there — before construction can begin, we need to award the contracts for the excavation and structural work. And that’s proving more complicated than expected. Our architect obtained and compared quotes from six different companies for the excavation and structural work. It turned out: the costs are in some cases significantly higher than we had originally planned.

It was clear: we had to rethink our construction plans and find ways to cut costs.

Why the Costs Are So High

It’s common for a building project to end up more expensive than initially planned. In our case, there are three reasons why the quotes were so high:

1. Massive Slab Thickness Due to Structural Requirements

A striking design feature of our house is the far cantilevered roof above the loggia and terrace. We really like this element — it also creates sheltered outdoor areas on the ground and lower floors. However, this design brings structural challenges: to keep the slab stable, it has to be built particularly massive — using lots of reinforced concrete. And reinforced concrete is expensive.

2. Isokorb with a High Unit Price

The Isokorb for thermal separation at the loggia are another particularly expensive item in the quotes. Isokorb prevent thermal bridges on cantilevered components like balconies. While we can use a more affordable model at the transition to the garage, the loggia requires a significantly more expensive version. We had to find an alternative.

3. Additional Excavation Due to the Foundation Pad

Our soil survey showed that we need a foundation pad made of gravel — one meter deep. This means a large amount of soil must be excavated, transported away, and replaced with expensive, compacted material.

Problem Solving

After the initial disappointment about the high costs, we focused on how we could save money — of course without sacrificing quality or long-term functionality. One element couldn’t be changed, but we found practical alternatives for the other two.

The Foundation Pad Stays as Is

The foundation pad is essential for the stability of the building ground and is required by the soil report. The additional costs for excavation and materials therefore can’t be avoided and must be included in our calculations.

Alternatives to Isokorb

Isokorb's are crucial for effective thermal insulation. However, we didn’t want to spend that much money on them and, together with our architect, found an alternative: we’re completely forgoing the thermal breaks and integrating the loggia directly into the external insulation system. This way, thermal separation is still ensured — but much more affordably.

This approach saves several thousand euros without functional drawbacks. At the transition to the adjacent garage, we will still install Isokorb to avoid thermal bridges to the heated part of the house. Here, we can go ahead with the more affordable model as planned.

Reducing Slab Thickness with Support Columns

One of the biggest cost drivers was the massive slab above the loggia and terrace. To reduce the structurally required thickness a bit — and thus the material costs — we’re now strategically adding steel support columns. One column will be placed outside, and three more inside on the ground floor. To make the interior columns less noticeable, they will be painted the same color as the window frames and positioned directly in front of them.

The exterior column is currently the biggest downside of our cost-saving measures — it interferes a bit with the “floating” appearance of the house. But it’s an acceptable compromise for us if it helps keep the construction costs from rising further.

Negotiation and Contracting

We re-planned and reduced costs. But who’s going to carry it out? We awarded the excavation work separately to a local excavation company. Two firms submitted suitable bids for the structural work, which differed only slightly in terms of execution and price. Our architecture firm had worked with both companies on previous projects and had good experiences with them.

Before making our final decision, we held project meetings with each company. Present were us as the future homeowners, our architect, the construction manager, and the managing directors of both companies. In these meetings, we were able to clarify open questions and even negotiate some discounts and price reductions.

The planned start of construction is end-April. Finally, some visible progress on our house project.

Excavation Work Offer

Structural Work Offer

The detailed quote with all itemized lists would go beyond the scope here, so we’re just sharing the summary. If you’re interested in specific items, we’re happy to go into more detail in the comments.