Can you please tell me which fire retardant coating suitable for exterior wooden decking and than complies to class 1 surface spread of flames BS476, part 7. and if this can be applied to decking already treated with normal decking varnish.
Zeroflame Fire Retardant Treatment can achieve UK Class 1/0 on timber decking boards but must be applied to a bare porous timber so the existing varnish would need to be removed. Once the treatment is fully dry, it can then be overcoated with a water based coating of your choice. We have no products/systems suitable for application over an existing varnish finish currently.