Regal renewal, renovation and expansion Palace Het Loo becomes increasingly visible

More than 30 years after Palace Het Loo opened as a museum, the palace is undergoing a major renovation and refurbishment. The work is being cleverly combined with an underground expansion of over 5,000 m², creating more space for temporary exhibitions and public facilities and allowing the extensive collection to be presented even better to visitors.

Text | Lieke van Zuilekom    Image | Paleis Het Loo

The work will be carried out in 6 lots: (1) the realization of a construction pit under the Bassecour (the forecourt), the wings and part of the Corps de Logis (main building); (2) the construction of a new, underground foyer in this construction pit, the renovation of the East and West wings and the renovation of the office and energy building; (3) the site layout, complete asbestos remediation and restoration of the monumental period rooms; (4) the E-installations; (5) the W-installations and (6) the elevators. The realization of lots 2 and 6 was awarded to BAM Bouw en Techniek - Region East after a European tender.

BAM Bouw en Techniek - Region East has constructed an underground extension with two floors on the front and one floor on the palace side, which will house several large museum rooms.

"The underground extension will be realized under the Bassecour (the forecourt)," says Marko Zwiers, construction site manager at BAM Bouw en Techniek. "For this we have realized a basement with two floors at the front and one floor on the palace side, in which several large museum rooms will be furnished. Visitors will walk from the Bassecour to the corner entrance pavilions from mid-2021. Via spacious staircases and elevators, they then enter a bright, underground entrance area that includes the box office and information desk, Museum Shop, checkroom and restrooms. Through a central hall, they gain access to the palace, as well as the museum rooms with temporary exhibitions and the 1,245-square-meter House of Orange, which will house a permanent collection of the royal family and provide access to the renovated East Wing. Through the west corner pavilion, you can also access the West Wing, where a special section for children will rise: the Junior Palace."

Concrete additive with microorganisms

For the realization of the underground extension, BAM Bouw en Techniek - Region East was provided with a temporary construction pit (Lot 1). "In this construction of underwater concrete and grout walls, we applied a levelling and insulation layer of cellular concrete," Zwiers says. "Then we poured a concrete floor almost 100 cm thick. This concrete floor was anchored into the subsoil with nearly 500 tension anchors." In the expansion, concrete walls as much as 80 to 100 cm thick are provided. "Because of the limited space, in addition to walls with double-sided formwork (concrete set formwork and closing formwork), single-sided walls were also used. The formwork for these single-sided walls was placed approximately one meter away from the temporary structure, after which the concrete was poured. This created a huge load on the formwork. Quite a challenge." A Self-Healing Agent additive from Basilisk, based on microorganisms that produce limestone, was added to the concrete for the basement floor and basement walls. "When unexpected leaks occur, these microorganisms are automatically activated. Hairline cracks up to 0.8 mm are then repaired autonomously, greatly improving the durability of the concrete."   

The construction for the underground extension has been completed for 85%. Currently, the deck of the first floor is being closed. For this, BAM Bouw en Techniek - Region East is using wide slabs (90%) in combination with hollow-core slabs (10%). "To maximize the use of the museum galleries, steel girders have been installed in the screed that allow spans of up to 25 meters." To ensure optimum daylighting in the underground extension, a large glass section was created in the deck, in the location of the former grass parterres. "At the front, several light slots have been added," Zwiers said. "In the museum galleries, artificial lighting will soon provide proper illumination."

Currently, the deck of the first floor is being closed.

Renewal of the East and West Wings.

The East and West wings will be stripped down to the shell. "On the outside, the wings will keep their familiar appearance," Zwiers says. "The existing structure will be partially renewed and weighted to allow for a higher user load. In addition, the layout will be changed." The biggest change will take place in the East Wing, as it connects directly to the underground extension over about 25 meters. "A temporary structure is provided in this wing to allow for the shell strip, jacking of the existing structure and erection of the new structure. Once this wing is stable again, the temporary structure will be removed. The wooden floors will remain largely intact. The windows will be insulated. In addition, all exterior walls will be insulated, in accordance with today's requirements."

To ensure optimal access to the new building, wings and the palace itself, 12 new elevator systems will be provided. "In the deck, we are creating a large freight elevator, with which all museum exhibits can be easily brought inside," Zwiers says. "The size of this elevator is carefully tuned. A number of modern glass elevators will be installed in the entrance building, and in the palace itself there will be elevators that match the finishes of the various rooms. The elevators will be supplied by a total of three elevator suppliers."