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Bobcat excavators remove soil from beneath Amsterdam’s world-famous canal houses

In Amsterdam, Dijkboom BV can regularly be found at the world-famous canal houses. Or rather, under the canal houses, because the company specializes in soil remediation, demolition and earthworks related to foundation repair and basement construction. This can be quite a challenge, especially in the capital, with its marshy peat soil, centuries-old wooden foundations and monumental buildings. But thanks to the use of Bobcat excavators, the work has become much easier, as a visit to one of Dijkboom's projects revealed.

Working on foundations or building cellars beneath canal houses in Amsterdam is no easy task due to the narrow streets, busy traffic and limited space. To access the underside of houses, a hole measuring one by two metres must first be dug in the garden, the sidewalk, or even in the public road alongside the house. Then, a passageway is broken or sawn through the existing wall of the exterior foundation or the facade. The hole and the passageway under the house are supported with sheet piles and steel beams to eliminate the risk of subsidence or collapse. Dijkboom then lowers a small Bobcat excavator into the hole, which begins excavating the soil beneath the house. Once there is sufficient space, the mini excavator can drive under the house, dig and transport the soil back through to the hole. There, a larger Bobcat excavator scoops it into containers, which then used to remove the soil—15 to 25 cubic metres per day, depending on the soil type and the available manoeuvring space.

To scoop soil from the hole next to the house in Amsterdam, Dijkboom uses a new recently delivered E55 mini excavator from Bobcat. The E55's boom has an extendable section, allowing it to be lengthened by 60 centimetres. This allows the machine to dig deeper, but also to reach directly from the street under the house. Depending on the surface, conveyor belts or Bobcat E10 excavators are used to transport the soil under the house. The E10 mini excavator is especially preferred for swampy ground with thin mud. Dijkboom has five of these: both diesel versions and an electric machine. The electric E10e is mainly used when the space under the house is difficult to ventilate. Dijkboom uses various attachments such as a demolition hammer, grapples and various buckets. The company had a special stainless steel bucket designed to prevent mud or sludge from sticking, which greatly improves productivity.

On this site, a basement is being built beneath a townhouse in Amsterdam. The building's floor area is approximately 12 by 12 metres. A small 6 by 6 metre basement already existed beneath part of the house; the remainder of the floor only covered a crawl space about 60 centimetres high. The ground beneath the house is being excavated to a depth of approximately three metres. The groundwater level is very high, meaning that despite the use of a water pump, a thick layer of sludge is constantly forming, which the machinery must operate within. Once the desired depth is reached, drainage will be installed on the ground, a layer of sand approximately 10 centimetres thick will be added, and a 30 centimetre thick reinforced concrete floor will be poured on top. Ultimately, the new basement will have a headroom of approximately 2.4 metres.

If necessary, demolition work and improvements or special modifications will also be made to the existing foundation, after which a contractor will complete the basement. Like most old Amsterdam buildings, the mansion in question has wooden piles beneath it, on which, after the underlayment, a foundation was once laid. These piles have a diameter of about 30 centimetres and can reach lengths of up to 14 metres, creating a solid sand layer.

In preparation for the projects, thorough soil and foundation investigations are carried out to assess the feasibility of building a basement. Measurements are also taken on the exterior of the facades before and during construction to ensure the building doesn't subside as a result of the work. Archaeological investigations are sometimes also conducted during construction in certain locations throughout the city.

According to Johan Eikelenboom, co-owner of Dijkboom, the project in Amsterdam is a good example of the type of projects Dijkboom primarily undertakes in Rotterdam and Amsterdam. "In those cities, there are many problems with old foundations, but in this project, the foundation is in reasonable condition. And there's a relatively large amount of space here, because the house has a small front garden and is located next to a parking lot. There was enough space at the house for the hole and the E55, and several containers for soil disposal, a compressor, and a site hut could be placed along the road. In narrow streets, we have to make the hole indoors in the floor, which means the residents have to leave their homes during the work."

Dijkboom's projects often start with foundation repairs, but because people want more living space, building a basement is an attractive option. This represents a significant investment, but according to Eikelenboom, there are many possibilities. "We've worked on projects where swimming pools, garages and a movie theatre were built under houses."

Dijkboom is a sister company of Anton van Dijk Demolition, a company that also operates around twenty Bobcat machines. They were all supplied by the Authorised Dealer, Inter-Techno, which incidentally serves many clients in the demolition sector because the small Bobcat mini-excavators and skid-steer loaders are ideal for use indoors and in tight spaces. Klaas van der Vis, operator on the project in Amsterdam, is particularly clear about this: "The Bobcat mini-excavators are perfect for our work. They are small, low and quiet, and they operate a full workday without any problems."

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