Gutex Multitherm Wall Installation - Hints & Tips

Roman Szypura of Clioma House and David Broderick of DB Plaster discuss the installation of Gutex Multitherm natural wood fibre insulation boards onto a wall. Includes hints on corner joints and how to install the last row beneath the eaves without damaging the boards.

[@Dschuyler707]

Just started learning about Gutex boards. Do the Gutex boards act as a sheer wall as well as insulation or does there need to be plywood/osb added to provide for sheer strength? Thanks.

[@niallcrosson5859]

Hi Dustin. GUTEX boards are not tested for use as sheer boards on walls and roofs. For this purpose bracing should be supplied by ply, OSB or a suitable particle board such as our FINSA VAPOURSTOP (www.ecologicalbuildingsystems.com/product/superpan-vapourstop) or ELKA board (www.ecologicalbuildingsystems.com/product/elka-strong-board-p5-particle-board) internally.

[@Dschuyler707]

@@niallcrosson5859 got it thanks!

[@ArthurDentZaphodBeeb]

If you cut the back off the groove, could you add noggins/blocking to add strength back to the board? Do you need to add an air control membrane over the Gutex for air tightness or can you simply tape seams/use liquid flashing sealants?

[@niallcrosson5859]

Hi, you can cut off the groove of the first board and if the overhang is adequate you can fix a "sheer block" to the rafter at the eaves. This would then be fixed to the rafter and would remove the need for sheer fixings as you move up the rafter. Only suction fixings are needed in this case.

[@niallcrosson5859]

IN terms of air/windtightness, the boards are inherently windtight thanks to there structure and t&g format. butt joints must be primed with TESCON SPRIMER/RP Primer and taped with TESCON VANA 150mm wide tape or AEROSANA VISCONN liquid air tight paint. Otherwise, a breather membrane such as SOLITEX PLUS can be applied over the whole roof, eliminating the need to seal butt joints. This is often the cheapest and easiest sealing method on complex roofs with lots of butt joints.

[@DeanSmith-ch1ep]

Could a trocal PVC membrane be installed directly on top of the gutex boards?

[@EcologicalBuildingSystems]

As a general rule we would not recommend to apply them directly on to Gutex. It is more preferable to create a well vented cavity between the Gutex and the external PVC membrane.

[@joel_fpv]

Are these available for purchase in the United States of America and Canada ?

[@EcologicalBuildingSystems]

We provide them for the UK and Ireland market www.ecologicalbuildingsystems.com/shop-by-brand/gutex. In the USA, you would need to speak to 475 Building Supplies foursevenfive.com/

[@joel_fpv]

@@EcologicalBuildingSystems thanks

[@tubulartuber]

What's the maximum thickness of Gutex that can be installed? IT is only limited by the availability of sufficiently long fasteners and spacing of fasteners?

[@EcologicalBuildingSystems]

Yes, in general, fastener length is the primary limitation. We have supplied up to 300mm Gutex on the external walls of a Passivhaus which used 500mm HECO screws.