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DURING THE DEFECTIVE CEMENT RENDER REMOVAL | | AFTER ALL REPAIR WORK FINISHED COMPLETED WITH A LIME RENDER | | AFTER ALL THE CEMENT/RENDER WAS REMOVED THERE WAS EXTENSVE REPAIR WORK UNDERTAKEN | | BEFORE FINISHING WITH COATS OF LIME RENDER |
Cement based renders can be disastrous for old buildings,because they are impermeable they trap moisture in the walls,also being rigid and inflexible they are prone to cracking as the seasons change and the walls naturaly flex.
Once cement renders start to crack they will allow rain in and that will be come trapped which can then lead to damp internally,and if left unchecked serious erosion of the masonry and decay of any woodwork can occur.
Replacing a cement based render with a breathable lime render will allow any moisture in the building fabric to discharge properly,thus allowing the wall to breathe.
It is obviously vital then that the correct materials and ratios be used, there are a variety of limes and sands available so it is possible to find a suitable render for any given situation.
As with any work, preparation is the key to a successful job,you can have the best materials and mixes possible but if the background is unstable,dirty,dusty,or not prepare correctly they will fail.