Hello Jerry,

The terraced house I live in was built in 1889, these old buildings were built to last using sandstone and Natural Hydraulic Lime (NHL) mortars.

As water evaporates off the surface of the set mortar the suction pulls more moisture to the exposed surface to evaporate, this suction helps to keep the sand stone dry and protect it.

Sadly nearly all the houses nearby have been pointed with non porous Portland Cement, this causes the moisture to be locked in to the sand stone longer causing surface fracturing and the stone surface turns to sand. This is caused by freeze / thawing that occurs in winter.

If the stone is painted this speeds up the process and after a few years when the paint comes away it reveals 3-5 mm of sand behind it.

I still think we could learn a thing or two from these old buildings and how they were constructed.

Thanks for reading