Behind a neoclassical facade in London, giant spiders will clamber over the steel frame of two atriums. But this idea belongs to Will Alsop rather than William Burroughs
People will stare aghast at the vision before them, high in the atrium. Clinging to the walls, giant spiderlike forms hover overhead. The spiders are all the more terrifying for their lurid orange and pink colouring. Occasionally, a stream of people appear to be sucked into the bodies of the creatures …

No, this scenario is not contrived on a temporary film set in the middle of nowhere; it is reality, in the form of Alsop Architects' pièce de résistance, soon to be incorporated into the refurbishment of Victoria House in central London.

What makes this vision all the more extraordinary is the fact the creatures will be housed within an existing office building, and are designed to attract rather than repel the occupants. The "spiders" are actually giant pods housing meeting rooms and will live in two new atriums proposed for the building. Their eight legs will be supported by the structural steelwork forming the atrium walls; bridges will connect the pods to the rest of the building. The two atriums, one at each end of the building, will form the centrepiece of the refurbishment. They are designed to act as a marketing draw to the young creatives that the developer is looking to attract.

Wolfgang Frese, senior architect on the project, says: "We wanted to make a feature for the atriums and create a family of elements that float in space." The family consists of one double-storey, fully enclosed pod, a smaller pod without a roof, likened by Frese to a soapdish, where more informal meetings can be held, and a much smaller transparent pod embedded in the floor, acting as skylight to the area below. Alsop wanted to paint the large pod orange and pink because, as Frese says, "it's an extraordinary form with an extraordinary colour".

Victoria House is a large neoclassical building fronting one side of Bloomsbury Square. It seems an unlikely setting for such a radical scheme as it has been barely altered since it was built in 1927. Its grade II-listing makes changes particularly difficult: English Heritage wouldn't allow external changes so Alsop had to concentrate on the interior.

Alsop Architects is very fond of its pods; they first popped up in Peckham Library, and the architect was keen to see them star in this refurbishment. Alsop even proposed pods for the exterior of the building when it was in the running in the competition for the headquarters for the GLA, but this came to nothing.

Luckily, behind the neoclassical facade lies an uncharacteristically modern steel frame, allowing the centre of the building to be opened out into two atriums. Alsop has managed to come up with a radical scheme for the building by modifying the existing lightwells to form the atriums. The steel frame will allow the lightwells' walls to be demolished and replaced by a steel and glass structure. Not content with a rectangular form, Alsop has pinched each atrium in the middle so that it is wider at the top and bottom. The office floorplates are being extended into this space creating additional floor space and an area in which to route the services.

Even though the pods appear to float in space, they are cleverly integrated into the rest of the building. The atrium structure features brackets on which the tapered steel legs of the large pods can sit. These act rather like the legs of a table supporting a "tabletop" made from steel beams. Two cantilevered bridges with glass balustrades connect the pod to the office floors; there is one for each storey of the meeting pod, each floor being separate from the other. The smaller single-storey soapdish pods feature a bridge spanning the atrium that doubles up as structural support for the pod located in the centre.

The proposed construction method for the pods is as progressive as the concept itself, and reflects how Alsop has moved on since Peckham Library.

The comparatively earthbound pods at Peckham are fairly conventional, being constructed from timber carcassing with a plywood skin. Wizz Consultancy has proposed a construction method for Victoria House that uses a balsa-wood core sandwiched between two layers of glass-reinforced plastic.

This wall is only 70 mm thick, thinner than at Peckham, and acts as a structural skin. The two layers of grp take the main loads, while the balsa – selected because it can be formed to the complex shape – takes the shear loading and connects the grp. This skin would be made as prefabricated panels and joined on site.

The large pods feature a second inner skin, made in the same way, which creates a cavity in which to run the services. Lightweight steel separates these skins; the cavity width varies according to how much room the services take up. The rest of the space is taken up with thermal and acoustic insulation. There wasn't room for conventional fan-coil units, so there is air intake and extract only. The temperature inside the pods is controlled by pipes carrying chilled or warm water, depending on the season. Small slot-like windows are used to retain the integrity of the shape, and additional light is provided through a skylight.

The soapdish pods are simpler because they are open to the atrium environment and feature integral seating made from foam and velvet.

The project is still in its early stages – planning permission was received in May, and the project is not due for completion until September next year. The specification for the pods will be put out as a performance package, so it is still possible that a wood skin will be used to build them if this proves more economic. Either way, the end result should look stunning. Interestingly, the construction technique and appearance of the large pods is not so dissimilar from a Jumbo jet, and this raises the question: what on earth will Alsop do next?