Sabine Marcelis's self-designed resin bathtub and three-metre-tall lava lamp feature in her Rotterdam family home, which she continuously reconfigures with her architect partner Paul Cournet.

"Our house is really a metaphor for how we like to live our lives," explained the designer, who spoke to Dezeen about the latest updates to the Coolhaven loft apartment she shares with Cournet and their two young children.

"It's forever evolving and very flexible," Marcelis added.

Set within a 500-square-metre space that was formerly a paper factory and then a bank, the apartment has been steadily designed by the couple over the last decade.

The light-filled, single-level home features a mix of pieces by Marcelis and Cournet, alongside bespoke furniture they commissioned from friends.

On one side of the space, the duo's bed is characterised by a blocky frame made of swirly timber. It is encircled by a netted curtain, which is suspended from the ceiling and can wrap around the furniture for privacy.

"We designed the bed just after our first baby as we needed a backrest," explained Marcelis. "Our previous one was more of a futon."

Marcelis and Cournet carved a cavernous, orange-coloured nook into the wall next to the sleeping area, which was fitted with an angular and stepped resin bathtub.

"At first, the bathroom was going to be behind a glass wall, but we decided to tear that wall down again and keep it open to the space," said Marcelis. "We live in that tub!"

An Osaka sofa, originally conceived by French designer Pierre Paulin in 1967, snakes across the floor opposite the bed.

Previously clad in a pink textile, the couch was recently reupholstered in a more pared-back beige.

"I felt that there was too much colour in the house," reflected Marcelis. "We still have the pink cover and we may go back to it again at some point. As our bed is in the main space, even when we change the sheets it feels like a totally different colour palette."

The designer placed a cylindrical lava lamp she created for British brand Mathmos next to the Osaka sofa. Measuring 2.96 metres in height, the oversized lighting encases rising and sinking "lava" rendered in a delicate shade of green.

On the other side of the loft, a squidgy, conversation pit-style sofa was positioned opposite a custom steel bookshelf by local designer Phil Proctor.

This living area can be sectioned off from the rest of the loft via a 10-metre-wide, floor-to-ceiling curtain printed with scans of pages from the notebooks of Berlin designer Ehsan Morshed Sefat.

"I love that it's functional, blocking the light and creating a more intimate space when we have our projector on, but it's also an artwork in itself," said Marcelis, who commissioned Morshed Sefat to design bedsheets for Germany's VitraHaus loft in the same way.

The designer stressed the importance of being "surrounded by friends" when selecting furniture for the loft, citing the many bespoke works that her peers created especially for the project.

"I don't really have any interest in living in my own showroom," said Marcelis. "The pieces we have in the house that Paul and I either designed together or alone came about out of necessity."

Marcelis and Cournet have plans to continue expanding their home.

"With each kid we have added a room to the house," explained Cournet.

"We recently purchased the ground floor [of the building] below the patio, and are planning to break through the floor and build a guest room there," said the architect. "I think the moment a house feels finished is the moment it stops being interesting."

As collaborators in life and design, Marcelis and Cournet recently worked together on the set design for the Cartier jewellery exhibition at the National Gallery of Victoria (NGV) in Melbourne, Australia, marking Marcelis's first exhibition design project.

Previously, the duo co-created the scenography for the Alula lounge at Milan design week 2024.

The photography is by Letizia Cigliutti.