# How to Calculate Geotextile QuantitiesJuly 03 2014

## First, the easy way...

Table of cover with 1.2m overlap for 4.5m wide Geotextile:-

This works out the number of strips that you need.
Multiply the number of strips by the length of each strip to calculate the amount required!
Simple!

## If you want to work it out the hard way... here's the algebra!

W = 3.3 n + P

### Let:

W = Width of Arena to be covered

L = Length of Arena to be covered

n = Number of strips of Geotextile required

P = Overlap specified

w = Width of Geotextile Roll

l = Length of Geotextile Roll

3.3 is derived from 4.5m (w) – 1.2m (P)

### Example (for a 40m Length x 20m Width arena):

20 = 3.3n + 1.2

and    3.3n = 20 – 1.2

n = (20 – 1.2) / 3.3 = 5.7 strips (use 6 no)

So:

l = (L + 0.5)6       (because we need length + 0.5m to dress up kicker)

l = (40 + 0.5)6     = 243m

or let 20m = L and 40m = W (laying the other way round)

n = (40-1.2)3.3    = 11.75 strips (use 12 no)

l = (20+0.5)12      = 246m

The rolls are 100m long so 3 rolls are required to complete the job.

# Geotextile JointsJune 23 2014

The geotextile should be laid such that any traffic on the site travels on the drainage stone layer not the fabric. Assuming a 20m x 40m Arena with the entrance gate in the 20m section the fabric, which is normally 4.5m wide, should be cut to a length of 20.5 metres. This should be laid at the furthest point from the entrance and stapled or glued or battened to the kicker rail along three sides to envelope the sand layer and provide a few centimetres of free board.

The next sheet to be laid will have an overlap of 1.2m (4 feet), so concertina the first sheet back this distance and reverse the lorry to its edge to top onto the sheet. Spread the sand to the required depth.

Lay the next sheet lapping under the first by 1.2m and using silicone sealer to gun a zig-zag seal down the middle of the join. The seal should be approximately 200mm (8”) from zig to zag and also 200mm (8”) from zig to zig.

Fix the edges of the sheet to the kicker board, concertina the end and proceed again as above.

As long as the system of a 1.2m overlap and a sealed joint is used the geotextile can, as required, be laid in any convenient direction. Similarly a join can be constructed when two lengths of geotextile are needed to incorporate a new roll.