Hi Clive, yes it is "how long is a piece of string"question but I'll try to give you some indication, the Elldiss I did a couple of week's ago was about 15ft internal, the delam was only between the seating kitchen and bathroom,ie the central corridor,the front end was'nt quite as bad as the central and rear area's,I used 2 full packs of the adhesive,of course the delam dos'nt cover the whole area rather it tend's to be in patches, when injecting you can feel the adhesive entering the void, when you feel resistance the delam either has'nt occured in that area or is'nt as bad. I realise the kits are quite pricey from the glue co but when you take into account the fact you don't have to lay out for new floor covering or someone to fit it works out about the same price. In my case once I'd bought the injection gun all I have to buy now is the adhesive and plug's.