Modern take on an old favourite

This Issue This is a part of the Materials and specifications feature

By - , Build 130

Used in its modern context, fibrous plaster can provide distinctive appeal to interiors by framing a space and adding crisp, sharp detail.

Detail for adding a fibrous plaster moulding.
A few examples of negative detail mouldings.

Most people associate fibrous plaster with grand historical buildings or old homes, conjuring up images of highly decorative ceilings, cornices, archways, corbels, niches and columns.

It’s harder to imagine that the same material has a place in modern residential and commercial construction, yet fibrous plaster is equally effective in modern environments as it is in traditional environments, and can provide one of the highest-quality finishes to the interior of a building.

Revealing clean lines

A popular modern construction detail where fibrous plaster comes into its own is the negative detail. This is designed to create clean, sharp lines that frame a space or separate planes, allowing one surface to seemingly float apart from another through the use of a reveal.

For negative details to be successful, the lines of the reveal must be straight, crisp and clean. While the design idea is classic and simple, the finished article is often less than perfect.

Most negative details are formed by fixing some sort of specially formed stopping angle or bead to the plasterboard lining and then stopping and finishing the combined board and bead areas – including inside the reveal. This is time-consuming precision work where the slightest of undulations in the surface will detract from the overall effect of the crispness and straightness of the line your eye is drawn to as a feature.

Handmade custom products

Fibrous plaster products are made by combining gypsum plaster and water with fibreglass reinforcement in a mould that is the negative shape of the finished product. The surface of the fibrous plaster product takes on the shape and finish of the surface of the mould in which it was cast.

Detail for adding a fibrous plaster moulding.

Once dry and installed – using a combination of adhesives, mechanical fixings, stopping and finishing compounds – fibrous plaster surfaces are ready for sealing and painting (oil-based sealers are recommended).

Because of the fibreglass reinforcement inside the plaster, fibrous plaster products are extremely tough and durable. Fibrous plaster products are made by hand, as are the moulds in which they are cast. Most of the 10 fibrous plaster factories operating in New Zealand specialise in creating moulds as well as castings – meaning custom products are their core business.

Mouldings remove need for stopping

Fibrous plaster negative-detail mouldings create the entire negative detail without the need for fixing bead or trim that then needs stopping and finishing. The moulding butts to the plasterboard lining, creating a standard join between two sheets that is stopped and finished in the conventional manner.

Because the negative-detail moulding is custom-made, the depth of the reveal and the overall height of the moulding can be made to suit the specific requirements of the job, taking into consideration the desired effect of the reveal, the stud height and the sheet lining sizes and set-out. It can also be made to suit the thickness of the sheet lining material – generally 10 or 13 mm – and be rebated for ease of jointing with horizontally fixed sheets or flat edged to suit vertically fixed sheets.

Negative details can also be used around door and window openings and in ceilings, defining areas or creating recesses for LED strip lighting.

Other modern fibrous plaster fixtures include lighting boxes and troughs for downlights, wall-mounted uplighting features, sculptural reception wall areas, straight-run cornices and battens. The only limit is the creativity of your local manufacturer.

A few examples of negative detail mouldings.

For more

To find a fibrous plaster manufacturer, visit the New Zealand Fibrous Plaster Association’s website

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Detail for adding a fibrous plaster moulding.
A few examples of negative detail mouldings.