John Bartram House – Historic Stucco/ Pointing Restoration
Mara restoration was contracted to perform the historic restoration of the stucco/pointing on the John Bartram House in Philadelphia. This particular task consisted of 100% re-pointing of the two end walls of the home, and stucco patching on the rear wall of the home. It was the desire of the design team to find a mortar mix that would match the color, texture, and finish of the stucco on the rear of the home. Since only patching of select locations was to be performed on the rear of the home it was imperative that the mortar match the existing material as closely as possible. This same mix design would then be used to point/stucco the side walls of the home even though the finished style of the mortar on the side walls would be completed in a more unfinished stucco look, with some of the wall stone showing through.
Our first step was to find what would be the base or primary color of the mortar. The material chosen to try and achieve this was a pre-blended lime based mortar, which was available in a variety of standard colors similar to the color we were trying to match. Using this type of pre-blended mortar provided us with the ability to create several different color and shade variations with a minimal amount of ingredients to mix and measure. This was also seen as very useful in achieving a high level of quality control when reproducing the same color over and over again through multiple batches.
Once this base mortar color was achieved the next step was to find the right blend of coarse aggregates to add to the base mortar and create the same appearance as those that are visible in the original mortar. Eight different colors and grades of gravel were initially selected. Several more samples were then performed by adding different gravel mixes and proportions to the base mix. The final mix consisted of 4 different types of gravel being added to the base mix. Three were added in during mixing and one, the largest, was added by hand after the mortar was put on the wall.
The final step in the process was to create the finished texture and bring the aggregates to the surface and make them visible. This was achieved in two separate steps. The first was performed while the mortar was being applied. After initial set of the mortar, while it was still green, it was rubbed with burlap to roughen the surface of the mortar as well as rub some of it off to expose the aggregate. The second was performed once the mortar had set for a minimum of 24 hours. A mild chemical cleaner was used and was agitated with stiff bristle brushes to remove the mortar haze and fully expose the colors of the gravel at the surface of the mortar.