Lean-to extensions often experience problems with roof leakages. If the water from the main roof of your house is discharged onto the roof of your lean-to extension, it’s likely that your roof will eventually begin to leak in heavy rain.This happens because the tiles and underlay of your extension are unable to cope with such a large volume of water. They will eventually cave under the pressure, leading to a leak. The best way to avoid this is to install guttering on your main roof which diverts the water away from the roof of your extension.