Got a leaky roof, close to the hip, near where the joists joints the wall plate. The roofers been up, re-bedded the two bottom ridge tiles, but can see nothing visibly wrong with the tiles. The problem is that my house was built in the 30's and the rosemary tiles are in good nick for their age, but there's no felt underneath them. Thinking laterally, was considering coating the area that appears to be where the problem is with expanding foam, in the hope of sealing the tiles together and stopping the water getting in...my first thought was put silicone under the tiles on the outside to physically seal them together. Comments please on the stupidity of either ( or both ) of the ideas. Cheers.