We live in a sub-division and treat the yard monthly and we spray the house but to no avail.
Spraying monthly won't do it...You are not controlling the subsequent generations...it takes aggressive treatment at first. Any live adult fleas will lay more eggs and you will have to start all over again..
You are after total extermination, not control.
The eggs will hatch every 3 days to 2 weeks, so even spraying every week is minimum and may not be enough at first. I'd spray inside every 3 days for the first two weeks, then weekly for the next six weeks. Not necessarily the whole house, but common areas and any area that has fleas present or the dog has access to. That's for indoors, and any favorite spots the dog lays when outdoors.
Bathe or dip the animal every 3 days for the first two weeks and then weekly until you gain a flea free environment. Permethrin has no effect on dog physiology unless the dog has a sensitivity, but then it may be something else in the shampoo. I just mix a half teaspoon of Permethrin in a couple of gallons of water or shampoo and soak the dog's coat. It takes a surprisingly small concentration of Permethrin to kill a flea, but you want the shampoo to stay in the hair for 20 minutes.
I use a hose and nozzle to carefully wash all the shampoo out and make sure there is no residual detergent remaining. That can cause dry skin and hot spots. But I think that can also be bacterial.
With my big dogs with heavy coats towels don't work very well so I take them outside and blow their hair out with an air nozzle on my compressor. I wish I had thought of doing that 30 years ago. It blows any dead fleas and shedding hair off too, and leaves an awesome fluffy look. 10 minutes of 120 psi air with a compressor is better than 10 hours with a brush to remove hair when they are shedding.
Of course you have to be very careful of eyes and noses and ears, but using your hand as a shield and controlling air pressure those areas can be done as well.
Anyway, It takes aggressive treatment for the first month, then a lesser spraying regimen and then the topical monthly treatments will work.
Keep some Borax powder laying around in the baseboards to kill any occasional stragglers.