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The method statement below should be followed to ensure joints remain fully permeable.

To alleviate the issues of maintenance associated with unbound permeable construction a permeable "drainage mortar" can be employed.
This allows the joints to be cleaned out without detriment to the structure and if properly constructed should structurally be zero maintenance throughout its service life.
Steintec produces a system of mortar for this type of construction using tuffbed 2-pack permeable bedding mortar, tuffbond priming mortar and tuff flow jointing mortar.


The required quantity of tuff flow jointing mortar can be calculated using our jointing mortar calculator.
Tuff flow jointing mortar is made up of 1 part tuffset G special purpose mortar and 4 parts tuffgrit aggregate blend.
125kg Tuff flow jointing mortar would, therefore, consist of 1 Qty. 25kg sack tuffset G special purpose mortar and 4 Qty. 25kg sacks tuffgrit aggregate blend.

Joint width and paver dimensions:
Due to the size of particles required to create a free-draining jointing mortar the joints need to be at least 10mm wide to enable application and effective flow.
Joint widths of between 8mm and 20mm are generally recommended.
The larger the paver the wider the joints need to be to drain the same amount of rainwater so for large paving slabs joints wider than 20mm can be installed however the permeable jointing mortar becomes more exposed and so the maintenance requirement can increase.

We recommend dark grey as the aggregate content is also dark and can become exposed over time with heavy footfall or vehicular traffic but in the case of domestic patios and driveways this is not such a concern and the mid grey and natural grey colours are an option.  Unlike our tufftop non-permeable jointing mortar the beige colour is not available.

We recommend designing permeable paving according to the SuDS manual recommendations relating to issues such as rainfall, catchment, flow rates, attenuation, etc.

We recommend following the guidelines of BS 7533 parts 4, 7, 10 & 12 in order to construct a structurally sound pavement according to the ground conditions and intended use.
Tuff flow jointing mortar should be assigned a 25N/mm2 mortar strength designation when referencing the above standard. 
Please contact our technical team in all cases for assistance