The boundaries are blurring these days. Gone are the days when luxury maisons were known for a single product category. Fashion houses are expanding into watches and fine jewellery, and high jewellers are opening resorts and launching furniture collections.

Montblanc's creative director Zaim Kamal, responsible for four different product offerings of the maison from watches to leather goods, writing instruments and jewellery, set up a whatsapp group for all members from his core design teams five months ago in order to communicate inspirations and ideas across the board. "The danger we face is we could end up with four different expressions within the maison," Kamal says. "We always try to align our work as much as we can. Our teams are used to the way of working via whatsapp, emails, texts and more. So if I send an inspiration to the group for the watch team, everyone else can also be a part of it."

As luxury brands evolve into lifestyle houses, the synergy among different departments becomes increasingly important to ensure consistency and sustainability as well as avoiding brand dilution. Fashion collections come out at least four times a year, the development of watches and jewellery, however, can take years. To tackle the challenges, brands have come up with separate approaches to bring together their different departments for collaboration.

While Montblanc brings together collective team work by opening a communication channel directly with the design principal, Hermès, for example, develops yearly themes which inspire the creative direction for its fashion collections and accessories as well as watches and jewellery.

"Hermès' creations are guided by an annual theme to give rhythm to the collections," says Philippe Delhotal, creative director of La Montre Hermès. The art of flaneur - Hermès' theme for 2015 - sets the foundation for the luxury maison's different collections that ooze effortless city wanderer cool.

Other luxury brands revolve their many collections around the core business that closely embraces the identity and origins of the house heritage. Cartier and Bulgari, for example, cite their high-jewellery department as inspirations for accessories and leather goods.

"Our high-jewellery studio is the most important one in terms of number of people," says Pierre Rainero, Cartier's director of image, style and heritage. "We have regular meetings together with all the studio heads to share the creativity and style. Each collection from one studio is shared with all the others. Sometimes they work together on the same inspiration."

Bulgari's CEO Jean-Christophe Babin agrees that high-jewellery creations are the source of inspiration for watches and leather goods.

"There are a lot of synergies as we decided a few years ago that the jewellery signs should be the signs of creativity for the other divisions," Babin says. "Our leather bags such as the Serpenti bags and all other designs are inspired by our high-jewellery [motifs]. All the jewellery design codes are eventually shown in other categories."

For luxury fashion houses such as Chanel and Louis Vuitton, couture-esque details and innovations derived from their apparel collections are transferred to fine jewellery and watches. Chanel's extensive use of Maison Lesage embroidery on its haute couture collections, for example, inspired a series of limited-edition timepieces such as the Mademoiselle Prive. The timepiece features a delicate dial of a shooting star made with diamond embroidery by Maison Lesage.

Chanel's iconic ribbon motif is also seen in its latest high jewellery collection Talismans de Chanel. "The emblematic embroidery by Maison Lesage which decorated Chanel's timepieces is the first time Lesage applied its haute couture skills to watch dials," says Benjamin Comar, Chanel's international fine jewellery director. Louis Vuitton reinterpreted the signature rope pattern painted by Christopher Nemeth who inspired the autumn/winter 2015 men's collection. The brand projected it on to the dial of the Tambour Damier Rope in a limited series of 50 pieces.

"It takes 12 to 15 months to develop new watches so having the right team is important," says Hamdi Chatti, Louis Vuitton's vice-president of watches and jewellery who worked closely with Vuitton's menswear designer Kim Jones on developing the Nemeth timepiece.

"Our designers, either for fashion or watches and jewellery, share with other departments the new projects they are working on. They work together and challenge each other within the Louis Vuitton universe. It's one of the house's strengths."

To create the Tambour Damier Rope piece, Chatti says his team was first briefed by Jones as he developed the ready-to-wear collection to achieve a watch dial featuring the key motif of the collection. Dial makers then experimented with different approaches to create a three-dimensional effect consistent with the house's aesthetics.

Similar to the collaboration achieved at Louis Vuitton and Chanel, different departments leverage on each other's artisanal know-how to develop new creations.

"Our different metiers departments inspire each other. We recently reproduced Hermès' famous silkscreen prints on a much smaller scale and onto the watch dials," Hermès' Delhotal says. A shared vision of house style eventually brings together all the cross-department creativities and collaborations. "All of Chanel's activities are part of one single house of luxury," Comar says. "They share the same values of creation and have a common heritage. And as all métiers are developed side by side, it is only natural that the constantly renewed creativity of [some] should feed the others."

"We have to have one centralised vision which we define at the beginning of the year, who we design for," Montblanc's Kamal says. "So whenever you look at the overall picture, there's always coherency." Bulgari's Babin also recognises the importance of the consistency of design codes. "It's important to make sure that the codes are not interpreted in too many different ways," he says.

With fashion power players such as Burberry and Marc Jacobs shuttering diffusion lines and consolidating various labels, more streamlined operations appear to be on the horizon for luxury brands.