Just a footnote on some research over the last couple of days.
Intumescent products do not seem to be the way to go here. Intumescent expanding foam is available but manufacturer's tech support was unequivocal about its reaction with PVC insulation - "fizzing has been observed" (!). Intumescent mastics and (non-setting) intumescent putties are available but their use is another professional area. Intumescent mortars may be suitable but come in 20kg bags. Applications for industrial cabling come as firestops for ducts and cable trays - out of my league.
However fire retardant expanding foam is available which claims up to 4 hours fire and smoke resistance. Bostik technical support advise this definitely does not react with PVC (I think it is a modified PU foam). Incidentally Bostik manufacture the fire retardant foam sold by Wickes.
Will the mice like it? Well if they do I will adopt PrenticeBoyofDerry's suggestion and cut it back and top it off with 15mm of one coat plaster.
Intumescent products do not seem to be the way to go here. Intumescent expanding foam is available but manufacturer's tech support was unequivocal about its reaction with PVC insulation - "fizzing has been observed" (!). Intumescent mastics and (non-setting) intumescent putties are available but their use is another professional area. Intumescent mortars may be suitable but come in 20kg bags. Applications for industrial cabling come as firestops for ducts and cable trays - out of my league.
However fire retardant expanding foam is available which claims up to 4 hours fire and smoke resistance. Bostik technical support advise this definitely does not react with PVC (I think it is a modified PU foam). Incidentally Bostik manufacture the fire retardant foam sold by Wickes.
Will the mice like it? Well if they do I will adopt PrenticeBoyofDerry's suggestion and cut it back and top it off with 15mm of one coat plaster.
