MMC techniques

Some contractors use a mixture of technologies. Preplumbed hot water systems have been available for some time, as have electrical looms and associated services.

Floor and roof construction has also progressed. Prefabricated floor beams emerged a few years ago - they give longer spans, are less prone to squeak and come complete with knockouts for services. Whole floor and roof assemblies are now available. The floor is made to fit in the factory, from traditional flooring-grade chipboard, supported by a lattice of steel webs, large enough to receive waste pipes or light steel beams. Craned into position, they offer enormous savings on time and offer the benefit of being able to pass services through. Plasterboard ceilings however, are still site-fixed. The same principle applies to roof construction, where the contractor can order prefabricated roof assemblies which are rigid and insulated, to be installed, for example, in cross wall construction or from eaves to ridge.

BubbleDeck

BubbleDeck is a form of construction, which as the name implies, incorporates bubbles into the construction in order to reduce the dead weight. The concept has been popular in Denmark and Holland for over 10 years. The bubbles are created from incorporating recycled hollow plastic balls in between the steel reinforcement, before the concrete is poured.

Under manufactured conditions, the plastic bubbles are trapped between the top and bottom reinforcement, and cast into a concrete biscuit to create a semi-precast unit. The unit is then craned into position and concrete is poured on top, the lower section acting as permanent formwork.

The site concrete is poured on top to form a structural topping. The load transfers in two directions back to the columns or load bearing walls. The use of a splice rebar joint stitches the panels together to enable spans over 21 metres to be designed. In a more traditional form of precast concrete flooring, the floor 'planks' span from beam to beam in one direction, which in turn dictates the length of the span. These beams of steel or concrete can be seen to the underside of the floor and are known as 'downstand' beams. Bubble Deck construction eliminates the need for downstand beams.

How can you spot them? You can't, so look through the health and safety file and look for the absence of downstand beams. 

Figures 1-2: BubbleDeck

© Figures 1-2 are reproduced with permission from BubbleDeck. For more information go to BubbleDeck

Flooring

Figure 3: Timber PosiJoist floor cassette under construction off site

Figure 4: Finished PosiJoist floor cassette ready for shipment

Figure 5: PosiJoist floor cassette being lowered into position - note the deep service void beneath the floor finish

Figure 6: Floor construction nearing completion

© Figures 3-6 are reproduced with permission from AC Roof Trusses Ltd

Bathroom options

Figure 7: Accessible WC

Figure 8: Rear view of preplumbed services

Figure 9: Section of completed product

© Figures 7-9 are reproduced with permission from Concargo Composites