I have a single storey extension which when it rains heavily allows water into what was an exterior wall and is now the interior. The roof is a tiled roof and has lead flashing where it meets the exterior wall. The pitch of the roof however is quite shallow and I am wondering if during heavy rain and strong winds the water is being driven under the flashing. Can I silicone the bottom of the lead flashing to prevent this? Is there a recommended way of getting around this problem like maybe extending the width of the flashing. Any advice would be greatly appreciated.