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A. Proctor Group CLT Solutions

CLT (Cross laminated timber) is growing in popularity and can offer many advantages, as a sustainable energy efficient building method. It has been used in many construction projects, predominantly within the commercial sector such as schools and hospitals. CLT, is an engineered timber product, produced in a controlled factory environment from sustainably sourced timber. It is formed of kiln-dried spruce or pine boards which are laid on top of each other at 90° (three, five, seven or nine layers depending on structural requirements), and then coated with a layer of adhesive and subjected to immense hydraulic pressure to create large, stiff, dimensionally stable panels. Often referred to as ‘Super Plywood’, CLT offers high strength and the structural simplicity needed for cost-effective buildings, as well as a lighter environmental footprint than concrete or steel. It also provides numerous other benefits, including quicker installation, reduced waste, improved thermal performance and design versatility.

The STA have recognised this and produced a comprehensive document in March 2017 - The STA Advice Note 14, Robustness of CLT structures. This document provides good practice guidance for the design, detailing and installation of CLT building structures. A critical element to their successful use is to ensure good moisture management, as whilst the system is robust, poor installation can let the design down.

Fig 1 (produced by STA) shows how a CLT structure is built up with the correct installation of insulation, on the outside of the frame. The CLT should always be on the warm side of the insulation to avoid unnecessary moisture fluctuations, which also brings the added benefit of mitigating any potential cold bridging issues, as they are adequately catered for with the external envelope of continuous insulation. It is preferable for this insulation to be moisture open to allow the wall to breathe and reduce the risk of built-up moisture within the envelope. The cavity provides extra protection throughout the life of the building. The STA have produced further guidance in January this year (Laminate/Mass timber structures- Durability by Design Technical Note 23). This note concludes with some best practice advice which includes the following -

  • Ensure the external wall make up allows for vapour diffusion from the interior to exterior vented spaces (BS5250 standard to be referenced and followed in a design)
  • Air leakage control membranes and sealants checked to avoid moisture vapour traps
  • Thermal Insulation should be placed on the exterior side of the laminated mass timber panels.

Installation Guides
Material Properties
BIM Objects
UK Availability
Global Availability

Material Properties


Property Test Method Result
Roll Size 1.5 x 50 m
Thickness Calibrated Deadweight Micrometer 0.65 mm
Weight Electronic Weigh Scale 292 g/m2
Application Temperature - Air & Surface Minimum -10 C
Service Temperature -40 to 80 C
Water Penetration - Before Ageing EN 1928:2000 Method A W1 Class
Water Penetration - After Ageing EN 1928:2000 Method A W1 Class
Air Permeance EN 12114 0.01 m3/m2/hr @50Pa
Water Vapour Resistance Sd EN ISO 12572(C) 0.039 m
Water Vapour Transmission BS 3177:1959 893 g/m2/24hr
Peel Adhesion EN 1939 5.01 N/10mm
Tensile Strength - MD EN 12311-1 417 N
Tensile Strength - XD EN 12311-1 252 N
Tear Resistance - MD EN 12310-1 412 N
Tear Resistance - XD EN 12310-1 286 N
Dimensional Stability - MD EN 1107-2 0.3 %
Dimensional Stability - XD EN 1107-2 +0.1 %
Reaction to Fire EN 13501 - 1 B Class
Flexibility at Low Temperature EN 1109 No cracks at -40C

BIM Objects

File Format
Wraptite - BIM Object - Steel Frame IFC
Wraptite and Facadeshield UV - BIM Object - Steel Frame IFC
Wraptite - BIM Object - Steel Frame With Reflectite Tape Over Board Joints IFC
Wraptite - BIM Object - Steel Frame Wraptite Tape Over Board Joints IFC
Wraptite - BIM Object - Wraptite Tape Over Board Joints IFC
Wraptite - BIM Object - Ventilated Timber Frame With External Airtight Membrane Wraptite IFC
Wraptite - BIM Object - Ventilated Timber Frame With External Airtight Membrane And Wraptite Tape Over Board Joints IFC
Wraptite - BIM Object - Warm Roof Slate With Softwood Sarking RVT
Wraptite - BIM Object - Warm Roof Tile With Plywood Sarking RVT

UK Availability

North East Scotland & Islands
Linda Kay
Regional Sales Manager


South London & South East
Josephine Matchette
Regional Sales Manager


Wales & South West
Marc Blackie
Technical / Regional Sales Manager

07968215 755

North London & East England
Ben Cremer
Technical / Regional Sales Manager


Head Office
The Haugh

Kieran Basi
Regional Sales Manager


Anthony Ruth
Regional Sales Manager

Global Availability

North America
Jeff Dibdin
International Account Manager.


South America
Jeff Dibdin
International Account Manager.


Jeff Dibdin
International Account Manager.


Jeff Dibdin
International Account Manager.


Jeff Dibdin
International Account Manager.


Jeff Dibdin
International Account Manager.


BS 5250 gives good guidance in the moisture management of CLT structures. This advice incorporates many of the above principles and the placement of membranes to reduce the risk of damaging moisture issues.

The A. Proctor Group provide a self-adhered, vapour permeable, air tight “breather membrane” that can be installed either behind or in front of the insulation. This decision can be made dependent upon the project location, and works programme for follow on trades. In some circumstances it may be appropriate to utilise the membrane in both locations. Once Wraptite® is applied to the CLT on the outside, the envelope is immediately protected from water ingress such as rain during the construction, which may be beneficial if the insulation is not to be installed immediately. The unique properties of Wraptite also provide the airtight line on the external side of the CLT panels offering, long term protection, and less risk of damages to the airtight layer from internal finishes. The high vapour permeability of the Wraptite provides the “breathing wall” which will help reduce any potential moisture build up that may have happened during the build process and wet trades.

As Wraptite is vapour permeable, it is moisture neutral and protects the building from unwanted moisture build up once it is occupied, such as heating/everyday occupier activities. Its characteristics therefore keep the envelope free from the risks of interstitial condensation.

Once the insulation is installed, depending on its type, it may be advisable to install a second layer, this time on the cold face of (outside) the insulation, to avoid moisture pick up through the insulation and potential loss of thermal performance. This can include the use of a reflective material to fur ther enhance the thermal performance of the structure, this time with APG vapour permeable Reflectashield® TF 0.81.

For any moisture concerns or questions, The A. Proctor Group have years of experience in across all areas of the building envelope, such as pitched roofs, walls and floors. Our team of technical exper ts at Head Office and external Regional Technical Sales Managers are all very well educated in the companies HAMM (Heat Air Moisture Movement) principles to ensure an effective balance is reached, ensuring a healthy building envelope.

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  01250 872 261

  01250 872 727


  A. Proctor Group Ltd., The Haugh, Blairgowrie, PH10 7ER





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