I’m currently having part of a late 19th century wall repointed with lime. Some of the original pointing is sound and where that’s the case, I’m leaving it alone. The ‘Bricky’ doing the pointing believes that the parts of the wall with original ‘sound’ pointing was probably done with ‘Roman cement’ as its fairly hard and a whitish grey colour but he doesn’t know what the mix would have consisted of. Dose any body know what Roman cement is and what the mix would have consisted of around the 1880 period?
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Flyfisher
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Curiosity led me to this: http://en.wikipedia.org/wiki/Roman_cement
I hope mine is natural cement and not artificial. It seems however from the Wikipedia article that the artificial stuff came along in 1860 which suggests that mine could be the latter.
This widens my question. The front elevation of my building (from about the 1880’s) is completely covered in a rusticated render i.e. shaped to look like stone blocks around door ways and over windows which I guess is the same stuff as the pointing in the wall, but again not sure if its natural or artificial cement render? One good thing though, the Roman cement mortar in the old brickwork wall which is currently being repointed certainly hasn’t damaged the brickwork in its 130 year life
I’m also not sure if I should be concerned about breathability with this render. Dose natural cement breath? I’m sure the artificial stuff doesn’t. The ‘Bricky’ told me that he once saw a roman cement rendered chimney that had a lime patchwork repair. Because the lime allowed the water to get in, it caused further damage to the roman cement (i.e. water got behind it)and to the chimney itself which beggars the question how should I repair the render to the front of my property should the need arise?
This widens my question. The front elevation of my building (from about the 1880’s) is completely covered in a rusticated render i.e. shaped to look like stone blocks around door ways and over windows which I guess is the same stuff as the pointing in the wall, but again not sure if its natural or artificial cement render? One good thing though, the Roman cement mortar in the old brickwork wall which is currently being repointed certainly hasn’t damaged the brickwork in its 130 year life
I’m also not sure if I should be concerned about breathability with this render. Dose natural cement breath? I’m sure the artificial stuff doesn’t. The ‘Bricky’ told me that he once saw a roman cement rendered chimney that had a lime patchwork repair. Because the lime allowed the water to get in, it caused further damage to the roman cement (i.e. water got behind it)and to the chimney itself which beggars the question how should I repair the render to the front of my property should the need arise?
Flyfisher
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Your description sounds as if it could be stucco, but I'm now way out of my comfort zone so hopefully a real expert will drop by shortly.
christianb
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I'm not sure about 'Roman Cement' as some kind of de facto product name, but the Romans did create their own type of cement (a Pozzolan) by adding materials such as powdered terracotta to lime putty - in effect this made the product 'hydraulic' thereby increasing its strength way above that of normal hydrated lime.
LadyArowana
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christianb said:
The Pantheon in Rome is a very impressive example of an unreinforced concrete dome, http://en.wikipedia.org/wiki/Pantheon,_Rome
As you point out along with the Wikipedia article above, my 19th Century Roman cement stucco render bares no resemblance to that used by the Romans. It was just a name coined by its inventor James Parker for his natural cement product and was subsequently used by other cement manufactures and imitators of the period. I am guessing that the surface has to stay water tight rather than breathable and so I am eager to know what I should use to repair any minor cracks. With regard to breathability, the inner face of the brickwork remains exposed in that it is only covered over with timber panels and lath plaster which stands a good inch or two proud of the wall.
Any stucco repair experts out there?
Any stucco repair experts out there?