The use of lime in building and as a binding material holding together stones and brick originates in our near past. Heated lime rock that was slaked with water gave early users of lime a paste for building that was superior to clay for building. The art of using lime as a plaster dates back to early civilizations. The compounds of lime mortars are oxides, hydroxides, hydrates and carbonates. The burning of limestone creates a chemical change between calcium oxide and carbon dioxide. The burning of the lime in the kiln removes impurity such as silica and a fine lime is produced.
The addition of water is known as slaking to produce a quick lime or calcium hydroxide or simply "mortar". Limes used in foundations in Massachusetts were:
a) Run of Kiln Lime - The product that comes from the kiln with out any sort of preparation.
b) Selected lump Lime - a well. burned lime which has been sorted and freed from core ashes and cinder by sorting.
c) Ground Pulverized Lime - Lime which has been reduced in size to pass through a 1/4 screen.
d) Hydrated Lime - A dry flocculent powder resulting from the treatment of quick lime with enough water to satisfy the calcium oxide.
In recent years a method of treating lime with water has been introduced that satisfies the chemical requirements of calcium oxide forming a dry, finely divided powder, the aforementioned hydrated lime. This product comes to the market in bags for use and simply add water and sand. Naturally Hydrated or Hydraulic Lime Putty.
At Thompson Crowley Masonry our family has been restoring lime masonry in Massachusetts since the 1960's. Our grandfather learned masonry in Ireland and England prior to that. Learning how to work with lime masonry in England he was qualified to work and excel in Massachusetts masonry. At a young age the owner of Thompson Crowley was shown how to mix lime, sand and cement. White washing basements in Salem and Peabody as a young boy over thirty years ago. Our knowledge and experience in foundation restoration along with our stone masonry and brick skills make us a top choice for anyone looking to repair their historic foundation.
We have repaired 1000's of foundations and completely restored countless lime foundations over the decades.
In the past sand and hair was used for plastering and coating foundations. When building stone or bricks after 1810 foundations used a 10% or greater Portland cement ratio was used.
In cases where mortar requires a greater strength such as buildings or foundation it is advantageous to use Portland cement. Investigation by various historical authorities has proven the fact that hydrated lime and Portland cement can be mixed in any portion of 10% of hydrate to Portland cement for making a cement mortar to an addition of 10% of addition of Portland cement for making a hydrated lime mortar. Ratios used typically in early European and Massachusetts building were 65 cement .35 lime or 1 lime 5 sand.
The most popular lime mixtures used were:
Three to one - for example four bags Portland cement , one bag of hydrated lime = 500lbs and 1500 pounds of sand.
Cement - Hydrated Lime mortar for interior plastering or brick
one bag of Portland cement 100 pounds , 2 bags of lime 200 pounds and 1200 pounds of sand. this mix was used for scratch coats in plaster and basement white washing.
Early first period homes from 1600's and 1700's lime and sand were used. Natural Hydrated Lime mixes. Cinders and ash have been documented in some cases to represent a roman cement mix.
What to use today in historic basements through out Massachusetts. Lime is present in all mortars today to different degree's. We still use hand mixed Lime putty ratios when required. Keeping in mind also in waterproofing situations the greater the amount of Portland cement used in mortar the more of barrier it creates for waterproofing. If a home has soft bricks a medium grade mortar is required for bonding. Medium grade mortars consist of 6 parts sand , 1 part lime and 1 part Portland cement .
When repairing lime based masonry it is important to remove all aged flakey joints and then thoroughly hydrate the existing masonry cement before repairing. Not only do you remove all loose cement by re-hydrating it helps when applying new mortar. If you were to just apply new mortar over aged lime joints the old sand and lime would absorb the water in the mortar and create a poor bond or cracking.
When working with historic foundations we are careful to restore the structural integrity of the walls by setting loose stones and bricks. We make sure to set the stone that are loose rather than rely on the mortars. Lime mortar acts as a cushion rather than glue. A properly laid foundation stone will sit on its own and not require mortar to hold it in place. Brick replacement of damaged bricks that may be spalling or deteriorating. Brick pointing with a rich lime mix allows for waterproofing, a better bond of hard and soft bricks and full support of the foundation. Upon completion of all repairs a lime based coating can be added to all the walls to achieve a clean look and preservation of your basement.