Simple Recipes For Making Compatible Repointing And Historic Masonry
Repair Mortars Using DGM To Duplicate Certain Historic Masonry Details

The following information contains recipes for achieving certain pointing colors and textures using DGM (deGruchy Masonry) mortar. DGM mortars come in two forms. One is a prepared blend of binder/aggregate/pigments to which you just add water then mix to make premium replacement mortar for your specific applications. Mixing can be accomplished with a low RPM, High torque industrial electric drill and rigid paddle attachment mixing in five-gallon
pails if desired.

The second form of the DGM range of colors is a blend of binder/pigments to obtain certain base shades in which you add your own local sands to achieve the duplication of the original aggregates used. Mixing can be done with a low RPM, High torque industrial electric drill and rigid paddle attachment mixing in five-gallon pails for pointing or with a standard paddle mortar mixer parked by the sand pile. The advantage of the pre-bagged material with the sand is that mixing can take place on each level of scaffold if suitable conditions allow this and no sand piles or other bags of material except the DGM needs to be on the job site which ensures that the engineering of the mortar’s final properties designed to be used is kept in a high quality control environment.

There are options on which binder is to be used for compatibility with various applications.
Example: We can create any of our stock colors by using Natural Hydraulic Lime (NHL)/sand/oxide pigments for repointing and repair to historic buildings which were built with lime/sand bedding mortar. You need to know what you want in producing the final strength, modulus of elasticity and permeability which all can be modified by the use of different strength binders, (i.e. DGM Mortar with NHL 2, (Feeble Hydraulic), NHL 3.5 (Moderately Hydraulic), NHL 5 (Eminently Hydraulic) or Natural cement/Natural Hydraulic Lime blends.

By obtaining a DGM Mortar kit for $10 you will have readily on hand the 6 strips of mortar which you can hold up to the original mortar on a building and see if any are close to what appears to be the base shade of binders with color variations that you ascertain are suitable. Please call if you need service regarding where to mail samples for mortar analysis in order to decide which binder to use in the DGM mix or for exact duplication of a mortar not in the DGM range of stock colors.

The following recipes are examples only and does not constitute a specification. Specifications are job specific and generally require a site visit and formal agreement.
Panel #1

Common Bond in Brickwork

Upper: Modern, stiff mud, wire cut standard 7-5/8
          face brick pointed with mortar struck flat or
          as a flush joint to show aggregates

Mortar Mix: 1 part DGM 200 (brown/grayish) mortar
                2-1/2 parts sharp, well graded brown
                   sand from Pennsylvania's Lehigh River
                   which has naturally occurring black
                   coal fleck inclusions.

Lower: Historic, stiff mud, wire cut smooth
          Philadelphia Brick, an 8-1/4 face brick with
          Buttered joint

Mortar Mix: 1 part St. Astier 3.5 NHL
                 2-1/4 parts marble screenings
                 1/4 part sharp, screened white sand
Panel #2

Carolina variegated sandstone pointed in a **Beveled Ridge joint

Mortar Mix: 1 part DGM (standard white)
                 2-1/2 parts sharp, well-graded yellow
                     sand
Panel #3

Variegated siliceous Iron stone pointed in a Raised and Ruled White Ribbon joint over a neutral colored background mortar brushed flat

Background
Mortar Mix: 1 part DGM (standard grey) mortar
                 2-1/2 parts sharp, well graded yellow
                     sand

White Ribbon
Mortar Mix: 1 part DGM (standard white) mortar
                 2-1/2 parts sharp, well graded and
                     then screened white sand.
Panel #4

Diopsidic sandstone (Serpentine-like (green) pointed in a Cobweb Ribbon (cobweb also Serpentine-like (curves)!)

Mortar Mix: 1 part DGM (standard grey) mortar
                 2-1/2 parts sharp, well graded brown
                     sand
Panel #5

Limonitic sandstone (yellowish brown) pointed in a *Grapevine joint, (not to be confused with the commonly named grapevine joint in brickwork where in that case an incised 1/8 line is impressed into the wet mortar when striking with a grapevine jointer tool.)

Mortar Mix: 1/2 part DGM 100 (light brown/mud
                     colored)
                1/2 part DGM 250 (greenish ochre-
                     brown colored)
                2-1/2 parts sharp, well graded brown
                      sand
Panel #6

Appalachian Bluestone (a sedimentary sandstone) pointed in a **Beveled Ridge joint which had the yellow sand aggregates exposed for a weathered appearance

Mortar Mix: 1 part DGM 100 (light brown/mud
                     colored) mortar
                2-1/2 parts sharp, well graded yellow
                      concrete sand

(Inclusions of lime chunks were also added along with the sand aggregate to duplicate the imperfection often seen in weathered mortar where the original lime slaking left bits of calcium hydroxide not fully broken down in the putty and where weathering reveals such bits)
Panel #7

Exterior, weathered, (by exposing aggregates) brown coat plaster (AKA stucco, render). Inclusions of lime chunks (see note above) were dashed into the wet plaster

Mortar Mix: 1 part DGM 100 (light brown/mud
                     colored) mortar
                 1 part sharp, well graded brown sand
                 1 part brown concrete sand
Panel #8

Pennsylvania's Rockhill Granite, (trappe rock), pointed in a **Beveled Ridge joint which had the reddish/brown sand aggregates exposed for a distressed and weathered appearance

Mortar Mix: 1 part DGM 100 (light brown/mud
                     colored) mortar
                 1-1/2 parts sharp, well graded yellow
                     sand
                 1 part brown concrete sand
Panel #9

Philadelphia's Chestnut Hill Stone (Wissahickon Schist), pointed in a **Beveled Ridge joint

Mortar Mix: 1 part DGM 250 (greenish ochre-brown
                     colored) mortar
                 2-1/2 parts sharp, well graded yellow
                     sand with mica fleck inclusions
                     added to simulate the
                     Pennsylvania's Schuylkill River sand
                     which has naturally occurring shist
                     fleck inclusions.


*Using the modern grapevine jointer in brickwork is a form of what is also called "bastard pointing" whereby the genuine article which is being attempted to be copied is actually the ruled key and tuck point where the bed mortar receives a keyway into the first infill and then later tucked with usually a white or red colored lime putty. This "tuck pointing" was done to give a more formal, (gauged) appearance to a hand molded and irregular sized brick or irregular rubble, and a snecked rubble, stone wall. Bastard pointing in stonework is found in the forms of Ruled Ribbon jointing and further by Cobweb Ribbon jointing in both cases by the Raised Ribbon where material is added or raised to the base infill and not into a keyway first incised. It is also found in the form of Painted Ribbon where whitewash is used for the painted highlight lines in white, graphite black, etc. to create contrast.

Pencylling on both brick and stone joints is a form of trompe l'oeil where these colored limes are painted in straight thin lines on the joint. It really is a faux finish to what originally was genuinely designed to have depth and body to an infill material that would last longer as it wore away. New (colonial style) brick buildings, and reproductions of the same at historic sites, often get what is also called a Colonial style "grapevine jointing" the brickwork. This style is often being copied from the original buildings in which the remnant of the style hardly remains evident in regard to the in-fill of colored lime putty. It is often by an oversight, or by a new interpretation of only what is desired from what remains of the original style that the contrasting infill is not included in the new work. This oversight has happened to the degree that a new style all its own has been created, AKA the grapevine jointing in brickwork. Thus, now all repointing is often generically referred to as tuck pointing from the original meaning to tuck in the colored putty within the center of an incised joint. The grapevine joint in brickwork is now made with a jointer which makes a center impression which is close to straight, but not at all as straight as when using a rule to guide the impression. In nature a real grape vine would never normally grow in straight lines or be incised, unless you are pulling a grapevine out of a building's mortar. Therefore it is just the grapevine joint in stonework which remains true to its name as a convex protrusion. In brickwork, the grapevine joint is a style of modern times. In brickwork a convex protrusion is called a beaded joint.

A very authentic historic style of pointing whereby a squared appearance is given to snecked rubble work is the Overhung Ridge joint. Snecked rubble is stonework cut in semi-squared blocks of stone laid in level, uniform coursing. Snecked rubble is sometimes wrongly referred to as Ashlar work. Ashlar work is actually perfectly squared blocks of stone, whether they be actually squares or rectangles, with very tight, (usually less than ¼) joinery. The Overhung Ridge joint is often misinterpreted as one of the ribbon joints mentioned above. Overhung Ridge is a joint that meets the flush face of the semi-squared block of stone above it, having a trailing edge to the stone above it and a ruled edge with a inward bevel meeting to the stone below it. Usually the left side of the head joint has the trailing edge and the right side of the head joint, the ruled edge with bevel.
Overhung Ridge Joint

Note that often in Overhung Ridge pointing of snecked rubble stonework, the head joints can be perfectly perpendicular with the horizontally level bed joints or the head joints are angled from the level bedding plane. From a distance this joint appears to make the semi-squared stones seem more squarely shaped. It also makes the joints look a lot like a ribbon joint, which they are not. Although no painted lime lines or additionally material is added on the surface of the ruled lines, the tightly compressed flat area of the Overhung Ridge joint typically dries lighter than the trailing and ruled edge which is scraped away to bleed into the surrounding texture of stone. This gives the appearance of a painted ribbon joint, but is not to say that in some instances pencylling was not still carried out. In Chestnut Hill, Philadelphia many original Overhung Ridge pointed buildings throughout Germantown Avenue and all the surrounding side streets can still be viewed.

**Beveled Ridge is also known in various areas as a Beveled Ridge, Colonial Ridge, Inverted-V, V, Beaked, Peaked, Prism, Crown Ridge or as a Pointed joint along with other regional terms for the same thing. The term for placing mortar between any irregularly shaped stone or brick where the mortared sides of the squared unit and/or bed was not first buttered with mortar and then dipped on to its bed is called pointing or it is called repointing when it is renewed. An actually pointed joint, which comes to a peak in the center best describes the most functional shape for mortar placed between irregular sized, random laid rubble stonework because the protrusion of the mortar allows for more material to be weathered away than any joint which is struck back. It also happens that rain coming at an angle toward the building would deflect away from the wall when the force of the rain hits a beveled edge and bounces away. Finally, in randomly laid rubble stonework where the mosaic-like pieces of stone come together to form one unified wall, a hand struck Beveled Ridge joint follows the contours of the stones’ joinery. This allows the size of each bevel to conform with the opening which it fills. This is aesthetically pleasing and is further improved in aesthetic quality when sunlight casts shadows on the lower half of the bevel making wide joints appear half their size. So, the terms Pointing and to Repoint may have remained because of the shape that mortar for this type of stonework was originally designed to have.

Surface pointing, (also known as a "scrub joint" ) is commonly applied as a pasted joint with little depth of material. It is in fact the most common method of "repointing" a whole building but contributes very little. In fact many times this method accelerates deterioration by trapping water in the wall with high concentrations of Portland cement in the mix used.

Many "Restoration masons" utilize this method because pasting over the top of slightly recessed joints with a thin overlay goes up very quickly and gives the appearance of a lot of work received for what is a small amount of money charged for the work. In the end, the less savvy homeowner thinks that since the entire wall has been "repointed" the uniform look of all joints being filled is a complete job and they received a good value.

What actually has happened is that the joint profile is not restored to a tooling within the edges of the brickwork but instead is now a flat joint on the faces of the brickwork much wider than the original joint profile.

The fineness of Portland cement and fine play sand made in a 1:1 ratio with little or no lime content is what makes this fine paste. The brittle, often gray Portland cement colored, scrub joint cracks and falls out within a few years.

Where it does not fall out and was filled into deeper voids it helps to keep moisture trapped in the bedding mortar and only allows any moisture in the wall to escape through the face of the masonry unit, if it were to get out at all. A resulting "picture frame" of proud gray mortar remains with hollowed back masonry units as the final irreversible damage. "Tuck pointing" is what some inappropriately call the scrub joint. The scrub joint is very similar to grouting the face of tile although the scrub joint is applied course by course on the brick joints. The actual root of the name "Tuck pointing" comes from a narrow keyway cut into the center of a molded brick joint and then filled or "tucked" with a bright white, red or black lime putty to give a more formal and gauged appearance to the brickwork.

Prior to the tucking in of this lime putty a red color wash is first applied to the bricks and mortar joints to give uniformity and aid as a shelter coat. Remnants of this color wash and infill of putty can be found on many historic brick buildings in the eastern states. The "grapevine joint" has taken the place for the name of a true ruled key and tucked joint and what is often reproduced in a restoration effort is simply the grapevine joint without the proper color wash and lime putty in-fill.
Example of “stone-filled framing” often found in early house construction. This is not how the interior walls were intended to remain. Owners in later years took off the interior plaster and exposed the brick or stone-filled framing and pointed up the work. This cobweb ribbon style mortar joint is considered a “bastard pointing.” It was not achieved by white material placed over grey background mortar nor was it painted on white lines. Simply by compressing the wet mortar in the center and scraping away and leaving an open texture to the feathered edges of the mortar did the centerline dry whiter and more prominent.
Another example of how the exterior plaster used to cover the rubble fieldstone foundation was “lined-out” to look like cut blocks of stone. The exterior plaster render above it is harling. A type of plaster harled (literally hurled) at the wall while wet.
An example of squirrel tail bake oven underside: Slates were used for the underside of a bake oven again arranged in the same successful pattern. Slate was an available local stone in the area of PA were this photo was taken.
            Small cullets of colorful glass galleted or embedded into wet render, (or in this case on concrete), is an enrichment or embellished effect of tessarae work.
The "grapevine" joint in stonework is a protruded bead. Easton, PA
The "beaded joint" in this brickwork is a protruded bead. Annapolis, MD
Metal sheets from late 1800's into early 1900's meant to reproduce the work of early brickmasons correctly interpreted a detailing that was found in most all brickwork where some detail, whether a bead or a tucked-joint ribbon or a slight raised "V" from cutting the lime mortar was always the finished profile instead of a concave striking commonly done today to cement mortars so that they are tightly compressed using a convex or "bucket" jointer. Unlike lime mortars, which allow absorption and evaporation of all water, modern Portland cement joints must keep water out by being tightly compressed.
 
 
Find the original whitewash on a building and you will often see bluing. Ultra Marine Blue was added as well as other types of bluing pigments to help a not so white limewash to become whiter. I have heard tales of superstitions about putting blue in the whitewash but I don't have substantial information to offer about whether they have any truth to the tales or not.
 
 
 
 
 
Example of "brick-filled framing" often found in early house construction.   Example using over-burned "clinker brick" which twists out of shape from over firing and then laid in a wall as a decorative form of brickwork called "skintled" brickwork.  
 
  A pent roof was removed from a rubble fieldstone farmhouse in Pennsylvania and the owner's who did this work showed me this beautiful original lime plaster which was "lined-out" to look like cut ashlar blocks of stone. For some reason we often see these blocks scribed around 26-27" long and 9" high. We have also measured many other variations but the 26 x 9 is common.  
  You know that you are dealing with historic fabric when you see greater detail in the use of lime/sand mortars. Above are down-draft kiln fired red brick with a pigmented red lime mortar. The black painted “ribbon joint” found on the stonework was originally installed to create a more formal appearance of gauged joinery. This creates contrast between the stone and the colors of the brick above it.  
  Another couple of examples of "lining out" where incised lines were scored into wet lime/sand exterior plaster to simulate brick and their joints. Although the mosaic of rubble fieldstone is considered a desirable thing of beauty today, it was more a sign of affluence to have had brick made and delivered to a building site rather that using scrap fieldstone laid up in a rubble wall. So, the shelter coat of lime/sand plaster was often embellished with lining-out to create something more sophisticated such as cut blocks of stone or expensive bricks.
 
  I would love someone to tell me what this is. A 250 year old threshold stone made of granite had an inlaid area. However, nothing was inlaid. The imprint of a center "mat-like" area is actually the original stone with only a vermiculated center area tooled in, as if to catch dirt. Something may have been poured in to the crevices and sat up on top of the stone but it is now worn completely away. Montgomery County, PA.  
Another example of Pencylling. Cut blocks of sandstone were colorwashed and pencylled-in with a ruled black line to give the appearance of even a closer tolerance to the stonework's joinery. The white part of the mortar would have been stained the uniform color applied to all of the stonework's faces and joints except for the prominent black line.
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