Phi Group

Retaining Walls | Timber Crib | Retaining Structures
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Permacrib Timber Crib Retaining Walls

Permacrib is a timber crib retaining wall system, utilising the long established gravity wall concept. The patented lightweight interlocking crib components form a series of open cell modules, these are then filled with well graded stone to create the mass required to counteract the earth pressures and surcharge loadings. Structural integrity is achieved through the interaction of the crib elements and the granular infill.


Permacrib may be used in major civil engineering retaining structures and simple landscaped walls. Additionally, Permacrib can be used to provide a landscaped and aesthetically pleasing face to reinforced earth or soil nailed structures. It can also act as a facing to sheet piling or concrete retaining walls, as well as creating vertical acoustic barriers.

Composition & Manufacture

Permacrib is manufactured from selected Radiata Pine softwood from managed, cultivated, renewable plantation resources. This ensures that environmental concerns for the conservation of resources and a sustainable future are met. Manufacturing is carried out to an approved Q.A. system ensuring a high level of dimensional accuracy. All machining is completed before treatment.


All components are pressure treated to BS8417:2011 using High Concentration Copper Azole preservative. Complete cell penetration is achieved to give full protection. Permacrib is treated and cured at U.K. plants which are subject to stringent environmental health controls and checks. All Permacrib components have a Desired Service Life of 60 years.

Economical & Flexible Design

Design versatility of the 8 readily available models enables header sizes to be mixed within the same structure for maximum economy or in major structures double or triple skin walls can be built. Face profiles can be varied to form benches to assist landscaping and enhance architectural appeal. Angle changes are easily formed and radii followed.


Permacrib is delivered to site in either standard component packs or in special packs tailored to suit particular structures or construction sequence requirements.

Technical Approval

British Board of Agrément Certificate No 95/3115 issued in 1995.  Patent protected.


Permacrib can be fully landscaped with a variety of plants in order to enhance its natural appearance, see our case studies section for examples of planted Permacrib retaining walls. 

Mitigation of Greenhouse Effects

Trees are the lungs of the earth - absorbing C02 and converting it to oxygen. Mature trees absorb less C02 therefore by harvesting and re-planting with young specimens a constant cycle of C02 absorption is ensured. Manufacture and construction are very simple and require low levels of energy.