POROTHERM Speed of Construction versus Concrete...

Wienerberger's Porotherm clay construction blocks are in their second year of use in New Zealand and we have almost completed our 2nd residential project in Putaruru as well as a Hamilton renovation. We have another project starting this month with four more scheduled over the next 3-4 months across NZ.

The speed of construction is one of the most queried aspects of this construction material and system. Is this system faster and cleaner to install?

With only eight blocks per m2 (500L x 249H x 250D), laying of the blocks is 36% faster than conventional concrete blocks at 12.5 per unit basis. The weight is similar for each when using comparible 240 concrete blocks which average at 18kgs each. The Porotherm blocks weigh in at 18-20kgs each.

Please find below an addition to an existing rammed earth house - we are showcasing this project which is now up to the plastering stage, and will keep you posted. The addition is a 63 m2 lounge area, and the walls went up in just under three days!

With only a 1mm thin bed mortar (applied horizontally by a specialised applicator) required for Porotherm (special end-of-block vertical key as part of the block's design eliminates vertical mortaring), the ease and speed of laying is considerably higher than forming and levelling a standard 10mm joint horizontally and vertically as carried out in standard concrete block construction. The laying of the blocks can be undertaken by suitably trained LBP block layers.

The first course is the only one laid on a mortar bed (10mm laser levelled), the remaining courses to roof truss height are all laid by this thin bed mortar method. A significant amount of preparation goes into laying the first course to ensure consecutive rows of blocks go up perfectly.

The speed of laying is increased considerably by the Porotherm blocks which are manufactured with an accuracy of 0.5mm over the length and width of the block. At 250mm wide, the block has excellent stability and the alignment level and plumb is fast and accurate. Preparation times for the Porotherm mortar and the quantities required are greatly reduced with less than 1% of the mortar used when compared to concrete block - this also comes with the associated saving in water.

All vertical structural steel (none required horizontally with Porotherm block except at foundation and bond beam level) is chemset into the floor, making the floor slab laying quick and accurate without the need to work around starter bars poured into the slab. This generally comprises 4/D12 cage and R10 ties @ 300. Ther vertical steel is chemset into the floor at 5.0m centres and each side of major openings greater than 1.5m2. No block washouts are necessary at floor level as the blocks are not solid poured - no block grout required.

Being an addition to an existing rammed earth home, the concrete portal required is shown here to connect the two structures.

All plumbing and electrical chases are solid plastered back to face level. All wall-face fixings use proprietary masonry fixing anchors for structural or cosmetic elements. 

Roof trusses on, openings prepared and waterproofed.