Restoration
Study The Original Methods and Materials
Our starting point in any restoration project is to take a thorough inventory of the original type of construction, as well as the original materials used in construction.
Understanding the long-term behavior of both the construction pathology and any materials used in restoration is, to us, the critical difference maker as to whether any restoration effort succeeds. Neglecting to do so could accelerate deterioration of the masonry, even to the point of structural failure. Using the right methods and materials, on the other hand, can extend the life of the structure for decades, and even hundreds of years. First and foremost, it is important to understand the differences between historic and modern masonry.
Traditional Masonry: Keep It Flexible and Permeable
One of the biggest differences between traditional and modern masonry are the way each type of construction handles movement and moisture.
In the simplest and most general terms, traditional masonry needs to breathe and move. Bricks, stones and lime mortars used in historic masonry are usually very permeable and absorb a great amount of moisture; likewise -- and importantly -- this characteristic permits its evaporation back out of the masonry, essentially making the masonry breathable. Movement in traditional masonry occurs through each mortar joint, as lime mortars, which are more flexible than contemporary cement-based mortars, act like cartilage for the masonry skeleton and can cushion expansion and contraction that naturally occur in brick or stone with temperature fluctuations.
Modern Masonry: Rigid and Watertight
As today's masonry is usually a protective skin or veneer over a structure of a different material, one of its main functions is to keep water out. Bricks, stone and mortars used in today's veneer work are now much more watertight than in the past. As regards movement, structural systems comprised of steel, concrete and lumber are much more rigid than their predecessors, and likewise so is the masonry on the exterior, especially the mortars (see our "Repointing" section). Movement in contemporary masonry generally occurs in what are called expansion joints; these joints are usually filled with flexible caulks.
Using Modern Treatments on Historic Masonry: Caution
Rigid, watertight mortars, film-forming paints, caulks and sealants appropriate for modern masonry can trap moisture in traditional structures as well as inhibit their natural movement mechanisms. The result, unfortunately, can be accelerated deterioration of historic masonry and sometimes even structural failure.
_____________________
Sample Projects: Restoration
Sample Project: Pointing and Structural Repair
Review of conditions: Gradual sheer and settlement cracks in 1850-era cobblestone house: harmful and unsightly repair work with cement-rich mortars; stone lintel over front door buckled and out of plumb.
Solutions: Remove previous repair work and repoint with matching lime mortar; reset loose cobbles as needed; stabilize and reset stone lintel to plumb.
______________________
Sample Project: Foundation Reconstruction
Review of conditions: front stone rubble foundation of 1820s-era farmhouse buckling due to poor drainage and lack of maintenance.
Solution: stabilize structure, excavate along foundation and rebuild front wall and stoop; install ground level drainage and regrade site.
Mason's Mark LLC P.O. Box 193 Kent, OH 44240 Phone (330) 671-6585 Fax(330) 678-6965