Restoration and Repair
Masonry restoration and repair requires an ability to adapt to a variety of existing masonry conditions and strike a balance between a structure's overall repair needs with the owner's budget. Every situation is different and therefore a great depth of experience is necessary to analyze the existing conditions and determine a practical approach that considers the long term health of the structure as well as the short term issues such as water penetration, structural damage, and inevitably; budget.
Most masonry structures built before 1920 were built using clay brick and lime mortar. This method of construction has certainly stood the test of time but failing to understand the role lime mortar plays in solid masonry construction could result in repairs that do more harm than good.
The lime mortar joints in this wall built in 1639, (right) still have visible pieces of oyster shell, unmixed lime, slag, and river sand.
More than half of the mortar joints shown in this picture, (above) have been repointed using lime mortar. The mortar joints have been repointed in a way that reduces the contrast between the repairs and the surrounding mortar joints.
Restoration and repair of older masonry buildings requires an understanding of how lime mortar differs from modern masonry cement. Modern masonry is built using cavity wall construction which is designed to prevent penetrating water from reaching interior walls. Solid masonry walls rely on the permeability of lime mortar to allow evaporation of penetrating water and water absorbed by porous clay brick. Modern cement is made using Portland cement which is a non permeable material that is incompatible with solid masonry built with lime mortar. Many problems can occur when Portland cement is used to repair walls that were built with lime mortar because water is not able to evaporate properly and often evaporates to interior walls causing damage to finishes. Portland cement is also a much more rigid material that doesn't allow mortar joints to flex when saturated brick go through expansion and contraction during freeze thaw cycles. Without no cushion to expand to expand at the edges, the face of the brick does more of the expanding and contracting which eventually causes the face of the brick to spall and crack.
Repairing masonry is not just about filling cracks with mortar. Many of our projects involve modern buildings that have to be repaired due to things like settlement cracks or even damage done by vehicles. Understanding the structural implications of every repair is important but the way the repair is finished can ruin the appearance of any structure. In some cases the selection of the wrong mortar colors combined with poor workmanship is so bad that any attempt to remove these bad repairs will do more damage to the brick or stone.
The following pictures are examples of bad workmanship being transformed into a finished product that blends with the surrounding masonry.
These pictures help to make the case that masonry repair and restoration has to consider more than just the structural function of the repair. Our repairs are done with great emphasis on the appearance. This sometimes involves fabricating new tools for striking, tinting mortar colors, brushing methods, moisture control, special aggregates, and shadowing techniques. It is not always possible to make a repair disappear as though it was never there, but the goal is to create as little contrast as possible between the restored masonry and the surrounding masonry.