Recently I have been redecorating the kitchen, the house is a ordinary terrace and I'm guessing it was built about 1940s. The back extension where the kitchen is was modified ( probably rebuilt) in the 70s.
After moving in many years ago a few months later the wood chip wall covering was going black and peeling from the walls. The builders were informed and blamed the problem on a calor gas heater, causing condensation, our plumber claimed there was no cavity wall as he noticed this putting in a waste for the washing machine. Later the builder removed the wall covering and tiled all the walls and to be fair they have been on the walls for over 30 years with no problem. However I have noticed that the inside of electrical sockets get wet ( or is it just the one near the kettle?)
Screw heads do rust. Anyway the tiles were very tired so I removed then,smoothed the walls,applied lining paper and then wallpaper ( tiling on a roll ) it all looks great but I'm worried the original problem may come back. I also moved the washing machine waste and did not encounter a cavity in the wall. My question is should I have a cavity or are some walls built differently.

calour gas or parrafin give out around one litre off water for every litre burnt so you need far more ventilation to get rid off the extra moisture