Smoking and contracts

Tax Planning and Financial

I would also like to add to my contract something regarding paying towards costs for repainting, cleaning curtains etc if the tenants leave and the house smells of smoke.(Being a non smoker I hate it, but feel that if I put non smokers on my ad for tenants it realy cuts down on applications, has anyone else found that happens?)
I use RLA Contracts so how could I go about adding any extra rules on to it that arent there??
Another thing I would like to add is that if they do not maintain the gardens then I will contract someone else to go and do it and bill them (it soon gets em getting the wellies out when I send out a reminder letter saying thats what I am going to do)