Chris
Yes mate sorry about this and not getting back to you earlier. We sealed some really porous concrete with Miraclke 511 Impregnator and got a coverage of around 16-18M2 per litre so 65-73ish per US Gallon.
I would calculate an average roof on a 3 Bedroom in this country at around 240M2 ish so 4 Gallons should do it with ease. Therefore based on the fact Miracle 511 costs around £70 a gallon trade the total cost should be £280 maximum. Added to this I still think it will go further on a roof.
Would you like me to send you a litre so you can do a coverage test on the exact type of roof???
Kev Martin
Tiling Logistics Ltd
