PermCalc is a free to use proprietary software package from Brett Landscaping that generates permeable pavement design suggestions from given input data. These design suggestions are based upon the information contained in BS7533: 13: 2009 Pavements constructed with clay, natural stone or concrete pavers Part 13: Guide for the design of permeable pavements constructed with concrete paving blocks and flags, natural stone slabs and setts and clay pavers published by the British Standards Institute.
However, the range of parameters in this British Standard (and the Interpave method) is limited; for example, the rainfall return period is limited to 1 event in 100 years +20% and the runoff rate is set to Greenfield run off rates of 7lt/sec/ha.
For sloping sites, it is necessary to calculate the reduction in storage capacity from first principles, whereas PermCalc checks and compensates automatically within the design.
Rainfall data is determined using information supplied by HR Wallingford Ltd.
PermCalc has the option to provide estimated construction costs based on default cost data for each component or construction task, but these default costs can be over-ridden and the client’s cost data used.
PermCalc will present the final design suggestion in the form of a PDF Output Document.
It is important to note that Brett Landscaping are offering the use of this calculator only to generate design suggestions. It does not replace the services of a consultant engineer, or other competent person, in providing a pavement design and estimated construction costs for a particular project.