ᐅ Strip foundation for garage with rainwater downpipe connection

Hello,
we are building a 6 x 6 m (20 x 20 ft) prefabricated reinforced concrete garage next to our house. We have already ordered the garage, but the strip foundation including the gutter connection is still missing. The excavator has already installed the drainage pipe close to the site. The first quote we received was 6,500 euros gross. That really surprised us. What are your experiences? Is that overpriced?

Hello,

to put your question into a professional context: For the strip foundation of a 36m² (387sq ft) reinforced concrete garage including the rain gutter connection, many individual cost items need to be considered – these include earthworks, formwork, reinforcement, concrete, drainage connection, material delivery, labor, and last but not least, site setup. Regional differences in labor and material costs, current workload of civil engineering companies, and increased construction material prices have caused prices to rise significantly in recent years. A gross price of 6,500 euros is indeed at the higher end but by no means an unusual outlier. An item like the rain gutter connection can noticeably increase the price, especially if elevation, infiltration requirements, or elaborate frost protection measures are required.

A price of around 180 to 250 euros per running meter of foundation is now quite common on average without a rainwater connection. With complete rainwater drainage and a precise, clean connection to the existing house drainage system, prices tend to reach the range you mentioned. It is occasionally possible to get lower prices, often at the expense of execution quality, site safety, or transparent cost disclosure. It does no harm to get a second or third quote while explicitly asking about the planned execution (thickness, reinforcement, embedment depth, degree of compaction, drainage details). Differences of a few hundred euros are easily explained by minor variations in scope of work.

Schnackischnak

Does the garage manufacturer possibly offer the option to also handle the foundation, or is it already too late for that? For us, it would have been significantly cheaper if we had used their partner company (we didn’t, due to scheduling reasons, but everything was chaotic at that time anyway). (Otherwise, not comparable in our case because we have a smaller garage, etc.)

Moustache schrieb:

We have ordered the garage; now we still need the strip foundation including the gutter connection. [...] The first quote was now a gross 6,500 Euro.

This is exactly why manufacturers of prefabricated garages often sell their products without foundations.

Besides, I avoid prefabricated double garages because, for logistical reasons, they consist of two parts: with single doors, the joint runs lengthwise, and they are two single garages each open as much as possible on the shared side; with a double-width door, the joint runs crosswise, splitting the garage into a front and rear half. In my opinion, double garages are therefore not suitable for modular building construction. But actually, the current high prices for these boxes are a strong enough argument for building the walls yourself.

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Thank you for your responses. A brief clarification: the offer does not include labor costs.

Last year, I paid roughly 3,000 gross for smoothing a 6x6 meter (20x20 feet) slab. It was done by the shell construction contractor as part of the house’s shell build.

I find your quote quite expensive. How many cubic meters of concrete do you need there? At those prices, I would do it myself. Maybe that could be an option for you as well.