HAVE WATER RUNNING DOWN BEHIND THE PLASTER IN ONE OF THE BEDROOMS, HAVE FIXED THE ROOFING PROBLEM THAT CAUSED THE WALL TO BECOME SATURATED BUT EVERY OTHER NIGHT IT SEEMS TO KEEP RELEASING WATER FROM SOMEWHERE. HAVE PUT A DEHUMIDIFIER IN THE ROOM TO TRY AND RECTIFY.
It would help if you provided some more detail.
I imagine its an outside wall, and that the roof flashing or tiles/slates have died/been blamed for the running water?
However, another possible cause is wind driven rain. Rain forced by high winds through the mortar of the wall. If you are in an exposed position and the rain is hitting the wall at wind speed it can find its way through a wall, through the thousands of holes left by your typical brickie, hence the theory of cavity walls, the rain comes through the outer wall and runs down the inside of the outer wall, then out through weep holes (if provided)
With a solid wall it gets as far as the plaster, then makes everything wet.
Is your wall solid or cavity?
The house is a end of terrace and is approx 100 yrs old so i would assume that the walls are solid and not cavity. The wall is south facing but is covered in rendering and have been told that rain has got behind it and has seaped through causing the inside of the wall to become saturated. The water only drains out of the brickwork during the early hours of the morning then stops during the day. It all seems very strange??.
This is a common problem!
The house would have been made with lime based mortar, this is good because during the course of a year the house heats up and cools down many times, the sun shining on the wall would get up to 40 odd degrees C in summer and below freezing in winter.
Lime mortar allows this movement without risk to the structure.
Probably, the render on the wall is not lime based, it cannot move to the same degree so it has cracked, probably in line with the bricks,
The rain has blown/been sucked into the wall and cannot escape.
The best solution is to take the render off and if the bricks are in good condition, re-point and then, decide what to do.
Possible solutions, paint with silicone, replace render(likely re-cracking in future) cover wall with cladding.
I prefer the latter, as you can leave a gap between the wall and the covering water proof material, for the air to rise through - this will lead to a dry warm wall.
Then there are many and varied outer layers, aluminum, wood, plastic, concrete - something to suit everyone.
You're not alone. I am going through a similar situation at the moment.
On my gable end the rendering came away where it meets the chimney (came away enough to fit your fingers down apparently!) and water has prentrated through to the plaster. Again my house is approx 100 years old with no cavity.
The rendering has been temporarily fixed until I totally replace next summer and I currently have a dehumidifier in the room, which has been there for a week now.
The wall does appear to be drying out in places but very very slowly. If I leave the dehumidifier off at night the wall appears worse the following morning, but presume this is just the existing moisture trying to get out onto the warmer side of the wall (the inside). Now the rendering has been fixed there is no other way for the damp to get out other than on the inside, so the dehumidifier does seem to be working for me.