Koi Pond Fibreglassing
There are many ways of fibreglassing a koi pond, and each fibreglasser will have their own preferred technique, the options you will find include using 1 layer of fibreglass matting, 2 layers and 2 layers plus a surface tissue. But to help you decide upon the right solution for you, you first need to understand what you actually want to achieve by fibreglassing (grp lining) your pond, firstly it needs to be waterproof, and secondly but more important it needs to be smooth with no projecting fibers.
"Please remember laying up fiberglass as a waterproof membrane on site in outdoor conditions is very different to laying up moulds in a factory environment"
I personally only use Lloyds approved materials and a top grade matting, this is very different from the cheap and cheerful matting and reblended resins that can be bought of ebay etc.
My recommended method of lay up (fibreglass application) is to use one layer of .600 grm CSM matting heavily filled with resin to ensure there are no pinholes. I choose not to “paddle roll” the material as this draws resin out to the front of the matting and can leave the back of the matting dry and with insufficient resin, it is for the same same reason that I choose not to apply a tissue coat.
After the lay up I hand sand the cured laminate to remove any projecting fibres, this ensures that there are no sharp protruding objects for your fish to catch themselves on, and then finish with a “flowcoat” of your chosen color, the two favorites are Black and British Racing Green.
Having said all that, please remember that I am happy to fiberglass your koi pool to any specification you may require, please do bear in mind that extra unrequired services requested or sheets of matting all have cost implications and my honest advice is to go for the one layer system which I have used for many years and can provide testimonials to confirm it's suitability for the job.
In short why pay extra for something you don’t need, 9/10 it is the persons inability to correctly lay up a one layer system that leads them to rely on a surface tissue to hope its waterproof.
As a koi keeper myself I like to leave any pool, whether big or small, in a condition suitable to put my own personal koi into and I am happy to supply a written guarantee for 25 years covering my work and materials, obviously this would not cover items such as pond collapse due to poor construction etc.