As a means of efficiency when building a Georgian Colonial cottage like the one pictured above, the original mason would have used off-cuts and remaining units which didn’t make the cut for inclusion in the dressed building front facade.
This ensured a quicker turnaround in construction by focusing on the architectural ‘viewpoint priority’.
That being said, you can also use traditional ribbon point to convert a random rubble stone wall into ‘square dressed’ ashlar. Not only does this method correct any cracking but it also cleans up the appearance of the wall to correlate with the dressed Georgian front facade.
You may also notice the removal of the render in the jambs of the window and door.
Render removal is a delicate process and is one done without machining. If you were to take a grinder to the render in order to remove instead of using a chisel or small bolster, you’d run the risk of removing, also, the tooling left on the jamb by the building mason.
Removal of the render on this window jamb exposes a secret! The original tooling from construction over 150 years ago!
Same window with render removed.
After discovering the tooling, the chisel direction in removing the render correlated with the chisel direction of the tooling underneath. This further protected the detail.
Lime Mortar has been used for over 6000 years. The pyramids of Giza are plastered with it. Castles throughout the world, buildings of all size and stature, all share one thing: lime mortar. Typically generated through the decomposition of seashells early on, the process of ‘slaking’ limestone by way of kiln/fire came about at a later stage.
As it was noted for it’s inherent abilities for adherence and flexibility, lime mortar has not only been used in stone building in order to bond stones together within the wall matrix but it also serves as an expansion joint; allowing for movement within the wall without destroying the stone itself. The following picture indicates natural deformation of a bluestone masonry wall where settlement or foundation failure has occurred to a minor degree.
With this inherent movement capability, lime mortar design is a key factor in the restoration, conservation and preservation of these buildings.
In relationship to mortar’s cementitious (cement/ oxide) component, lime, when used in traditional mortar mixes for laying and pointing stone, should always outweigh the amount of cement used.
Lime is still used in today’s concrete design as a plasticizer although chemical dispersants are becoming more predominate as they are more cost effective.