I have a brick gable end wall (circa. 1900, no cavity) that is externally rendered to about 5 ft (not sure what type of render). There is new damp inside and the painted plaster is blistering. The internal exposed brick fireplace is salty and crumbling. A builder has suggested rendering the inside of the house and that the brick is crumbly as it is "old". Not convinced. Surely rendering the inside is not going to stop the damp coming in and making the plaster fall off again? How do I know whether the render outside has failed? I have tapped it and it sounds hollow in places. I don't think it's rain coming down the chimney as I have damp at the opposite end of the rendered wall well away from any chimneys. Have checked levels and ventilation blocks, all ok. No gutters on gable end. What to do? Will pulling the outside render off help? Render has been on wall for over 10 years and does not touch floor :( .