Banding, Columns, Door & Window Surrounds Columns & Arches Medallions, Coping, Arches, Columns, & Banding Balustrades, Newel Piers, Sphere Finials, & Planters Pool & Wall Coping Garden Elements Pier Caps Commercial Signage
jQuery Horizontal Image Slider by WOWSlider.com v1.7m

DESIGN TIPS—POINTING OF JOINTS

 

The following are design tips for Pointing of Joints in cast stone material applications as well as additional explanations to better inform you of the various methods used and the preferences suggested when installing cast stone.

Pointing is required because mortar will shrink and harden from the face in. As mortar shrinks, hardens, and settles, the edge of the cast stone may become so stressed that spalling (chipping) can occur. Hardening of the mortar, along with settling and stress cracking at the edges creates an opportunity for moisture to get into the joints.

 

Tooled Joints vs. Raked Joints


It is important to understand the difference between tooled and raked joints and the implications of both.

 

Tooled joints are strongly recommended in many applications because it is a compacted surface where the mortar is forced against the bond surfaces of the masonry material. In the case of bed joints, it is above and below the joint. In the case of head joints, is on either side of the joint.

 

Raked joints are not compact against the surfaces of the joint. The front section of the mortar joint is scraped out. This scraping is called raking and can leave voids in the head and bed joints which can allow water penetration. Thus, proper procedures for raking and pointing of mortar joints must be adhered to for proper sealing of joints while preserving the integrity of the look of the finished cast stone project. Matching color mortar is usually applied on top of the raking in a concave fashion.

 

Although high pressure washing is not appropriate for cast stone cleaning, many masonry walls are aggressively cleaned with moderate to high water pressure and acidic solutions which can further open voids and separations. Caution should be applied when cleaning cast stone. Water pressure should not be stronger than hose pressure. The first attempt for cleaning solutions should be soap and water. If further cleaning is required, a mild acidic solution can be used, making sure that the stone is rinsed thoroughly and no collection of water and acidic solution is left at the base of the cast stone.

 

Mortar Joints vs. Sealant Joints

 

Mortar joints are usually three–eighths inch for exterior applications; mortar joints are anywhere between one–eighth inch to quarter inch for interior applications. Make sure that you have spacers so you have the same distance between each piece for symmetry.

 

Mortar joints are recommended for masonry bound trim such as keystones, quoins, date stones, inscription blocks, window surrounds, lintels and belt courses. It is recommended that one always rake joints back approximately one inch from the cast stone edge and point mortar joints. Place a mixture of mortar mix grouting that has been color matched in the top portion. Do not use the grey mortar for pointing. (Refer to our bulletins on recommendations for mortars and sealants.)

 

Soft Sealant Joints are recommended for conventional masonry units, head joints at coping stones, joints at column covers, cornices, soffits, window sills, platforms, and all stone sections with projecting profiles, exposed top joints, rigid suspension connections to the supporting structure, and when piece sizes are larger than conventional masonry units (one foot, six inches tall by two feet, six inches long for vertical applications).

 

Grey mortar is usually used for installation of cast stone material. Color matched mortar mix should be used for the top three–quarter inch to one inch of the joint.


Recommendations for setting of Cast Stone per Master Spec 04720 Sec 3.03
Coloring of Pointing Mortar

 

Grey mortar is not suggested for pointing. Matching the color of the pointing mortar to the color of the cast stone, or selecting a color a shade close to the original color is strongly suggested.

 

Sharp contrast of color in the pointing mortar can stain the cast stone, therefore it is strongly recommended that the color closely resembles that of the cast stone material. Carbon black or ultramarine blue pigments should not be used.

 

Colors must be natural or synthetic mineral oxides that meet ASTM C979 requirements of sun–fast, lime–proof, and alkali–resistant.

 

The amount of colorant must not exceed ten percent of the weight of the cement used.

 

Note that careful planning at the start will assist in eliminating disappointment for any homeowner or commercial designer at the completion of the project. Since a small color sample cannot represent a full image of what the entire project will become, it is always suggested that one invests in a mockup wall of the cast stone material. Since cast stone is cleaned after the installation, it is suggested that the mockup be cleaned with the same solution that the final project will be cleaned with.

 

DESIGN TIPS — POINTING OF JOINTS (PDF)

 

The information within this and all our bulletins has been provided as a guideline and based upon statistical data and prior uses. We always suggest that you consult with your engineer, architect or contractor for the best design and use of cast stone for your project. Our design team is always available to answer any of your questions. We do not accept any liability from damages resulting from your interpretation of the data contained within.