your burning the roots tendrils off so dosnt affect the brick or stone like building a a firepit and having a fire in it as that will explode with heat from the fireWhenever I want to kill it,I always cut it at the base,twice,2” between each cut,to stop it bridging.
@gaz1 ,too risky playing a torch near masonry,you get explosions due to moisture in the voids.
An appropriate herbicide is the easy/simple answer to the problem.
Petrol and a box of matches ?Such as?
I don’t think anyone was suggesting letting it grow inside a cavity wall