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Page 3
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| Finished job with original mistakes left in. |
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Stone
As with brick, save and use original materials when possible. But with stone, we quite often see original stone relayed improperly.
The old masons said, “Lay the stone the way it came out of the ground.” That is with the bed of the stone, the grain, parallel to the ground.
Now that I’m an old mason, I say it too. Don’t stand the grain up.
Stone laid grain up or perpendicular to the ground is exposing the stone to water infi ltration.
This rule often comes into play when a structure is moved from an old stone foundation to a new concrete foundation.
A concrete stone shelf is provided, usually 4- inches which is adequate for brick but not for stone (6 to 8 inches should be the width of the shelf).
Masons take the original load bearing stone and set it on the shelf with its grain up, in the manner of 1950’s veneer.
This is the quick and dirty way of making the original stones fi t a shelf. For proper restoration, the original stones must be back sawn to fit the shelf and laid in the original manner with the original faces facing out. |
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1803 townhouse. Marble entry in disrepair. Note concrete sidewalk has
risen 8” from original grade burying bottom step |
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Mortar
In the last six or eight years there has been a revolution in the restoration world - a return to true lime mortars.
We have always known that characteristics of the setting materials must be compatible with the brick and stone.
When soft brick is laid or repointed with hard mortar, the brick eventually suffers.
For years we fiddled with hydrated lime in attempts to trick Portland cement into looking and behaving like the old stuff.
Now, thanks to the pioneering work by the Scottish Lime Council in Edinburgh and American revolutionaries like Jimmy Price of Virginia Lime Works, we have the information and the materials available for proper mortars that will not harm our old buildings.
The new rule is simple. If it was originally built with lime mortars and plasters, it should be maintained and restored with the same.
Where Portland mortars were used over the years, this material needs to be carefully removed and the work redone with lime.
Jeff Price’s article in Structure magazine, “Yes, it does matter what mortar you use.” (STRUCTURE May 2004) is a wonderful introduction to this interesting and vast subject.
Don’t be afraid of the lime mortar that has survived thousands of years. |
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