Trenwyth / Astra-Glaze-SW+

Astra-Glaze-SW+ Installation

IMPORTANT! Before You Begin:

Northfield requires that you order a full size unit to illustrate color for approval. Northfield requires a sample panel be installed at the jobsite prior to installation of any Northfield products. This panel will represent the quality, color and texture of the product and the workmanship to be expected for the project. Either the owner or the project architect must approve the panel. Failure to produce a sample panel may result in loss of warranty. Northfield will provide 4″ units for a 4′ x 4′ sample panel at no cost for the material (not including freight to the site). Delivery, Storage and Handling
Glazed masonry units shall be delivered to the jobsite on banded pallets with individual protective covers on each glazed block face. Keep protective block covers on the blocks until installation. Store pallets in single stacks on level ground and cover with waterproof covering (e.g., tarpaulins) to protect the blocks from inclement weather. Handle blocks carefully to avoid breakage and damage to the finished surface.

Project Site Conditions:
Protection of Work: Cover walls, including open tops, each day after installation to keep open walls protected and dry. After units are installed they should be protected from damage by other trades performing operations that can stain or otherwise damage the finished surfaces by covering walls with plastic. Corners should be protected from damage after installation by covering them with plywood.

Do not, under any circumstance, install a damaged unit that does not conform to the requirements of ASTM C90 and ASTM C744 for the block and glazed face respectively. If units have been damaged during transit, contact Northfield immediately.

Laying Masonry Walls:
Draw blocks from more than one pallet at a time during installation. All exterior mortar shall include an approved water repellent additive added to each batch in the appropriate dosage rates for mortar type (M, S or N) per the manufacturer’s instructions. Refer to NCMA TEK Notes for Hot and Cold weather construction practices.

Lay Astra-Glaze-SW+ blocks with the faces level, plumb and true to a line strung horizontally at the glazed face. Install only quality units; reject all defective units, as defined in ASTM C744. Units shall have uniform face joint dimensions of 1/4″ both horizontally and vertically and 3/8″ on the unglazed side.

Tool joints neatly after they are finger-hard to make them straight and uniform. Size and place cut pieces appropriately to maintain consistency and bond. Complete masonry construction using procedures and workmanship consistent with the best masonry practices.

Lighting: Provide adequate lighting for masonry work by placing all lighting at a reasonable distance from the wall for even illumination. Do not use trough lighting.

Base Course: Align base course properly on the floor slab.

Cove Base: Keep the cove base tight to the slab if vinyl floor tile is to be installed. For thicker flooring, raise cove base units to the desired height.

Cutting: Make all unit cuts, including those for bonding, holes, boxes, etc., with motor driven masonry saws, using either an abrasive or diamond blade. Cut neatly and locate for best appearance.

Mortar Bedding and Jointing:

  1. Lay units with full mortar coverage on head and bed joints taking care not to block cores to be grouted or filled with masonry insulation.
  2. Tool all mortar joints when thumbprint hard into a concave configuration.
  3. Care should be taken to remove mortar from the face of masonry units before it sets.
  4. Tuckpoint the joints of scored units for proper appearance. All exterior scored units must be tuckpointed to prevent water penetration. Rake back the joint when epoxy (Bonsal/Laticrete) is used on select jobs that require better moisture prevention.

Recommended Mortars
In all exterior mortar, we recommend using the matching manufacturer-approved water-repellent mortar additive
. Follow manufacturer’s instructions. Consult manufacturer for recommendations.

Cleaning During Construction:
Keep walls clean daily during installation using brushes or rags and a clean damp cloth. Harsh cleaning methods after walls have been erected may mar the surface of the blocks. Do not allow excess mortar lumps or smears to harden on the glazed surfaces. Remove green mortar with a dry cloth. Do not use steel wool, sandpaper or other abrasives.

Flashing of Masonry Work:
Install flashing at locations shown in the plans and in strict accordance with the details and the best masonry flashing practices.

Weep Holes and Vents:
Install weep holes and vents at proper intervals at courses above grade, above flashing and at any water stops over windows, doors and beams. Consult NCMA TEK Notes for additional information on flashing.

The glazed facing shall conform to the requirements of ASTM C744-08 when viewed from a distance of five (5) feet at right angles to the wall with normal lighting. The concrete masonry units on which the glaze is molded shall conform to the requirements of ASTM C90.

Installation Recommendations:

  • For walls with a glazed finish on both sides, use two single-faced units. Because masonry units are typically installed aligning one side, the second side of double faced units is almost invariably misaligned. Use double-faced units only when economy is more important than appearance. Northfield accepts no responsibility for face alignment.
  • Cavity wall construction is recommended for exterior walls, with proper flashing, venting and weep holes.
  • For best appearance, use stack bond construction when stack bond appearance is desired (as opposed to scored units in running bond).
  • All exterior mortar joints must contain an approved water repellent additive. In all exterior mortar, we recommend using the matching an approved water-repellent mortar additive. Follow manufacturer’s instructions. Consult manufacturer for recommendations.
  • For best appearance and water resistance, tuckpoint scored joints on interior and exterior applications.
  • A complementary or matching mortar color is recommended when using colorful
    Astra-Glaze-SW+ units.

Grouting Walls Solid:
When filling walls with grout, proper detailing to remove moisture is even more critical. Follow masonry best practices and manufacturer’s recommendations for the installation of weep holes, vents and flashing.

Special Shapes and Colors:

  • Two different colors on one block. Any color can be put on one side of the block. And the same or any other color can be put on the other side of the same block.
  • No double bullnose units. Double bullnose units are not available because they cannot be drawn out of the molds. The molding methods will not accommodate double bullnose units on full-sized blocks. Some double bullnose Astra-Glaze-SW+ units are available in our 1″ and 2″ Shapes Series.

Joint Size:
The proper joint size to use when laying Astra-Glaze-SW+ block is 1/4″ at the face and 3/8″ at the unglazed concrete blocking.

The glazed face dimensions are 7 3/4″ x 15 3/4″, which allows a 1/4″ joint using modular coursing.

Installed With Other CMU Products Alignment:
If the face of a masonry wall involves different masonry products, it is necessary for the foreman to know the exact dimensions of each of the products to be installed in order to properly make bond when preparing the layout.

If the joint requirement for one of the products is 1/4″ and the other is 3/8″, this point must be taken into consideration when laying out the first course. If it’s not taken into consideration, the resulting finished wall will have unsightly misaligned vertical joints.

Astra-Glaze-SW+ units are specified in the wainscot of a corridor with Verastone, Verastone Plus, Trendstone or Trendstone Plus blocks above that point. Units have a single center score and the wall is in running bond.

The difficulty in holding a correct running bond is due to aligning the 3/8″ joints of the Verastone, Verastone Plus, Trendstone or Trendstone Plus units properly over the 1/4″ joints of Astra-Glaze-SW+.

Astra-Glaze-SW+ units must be laid using face joints of 1/4″ both vertically and horizontally. The Verastone, Verastone Plus, Trendstone or Trendstone Plus units being laid above must be centered over the 1/4″ joint of the Astra-Glaze-SW+ units which are already in place.

Depth Alignment:
Astra-Glaze-SW+ units are 1/8″ wider than standard CMU’s. Astra-Glaze-SW+ double-faced units are 1/4″ wider than standard CMU’s. This must be taken into consideration in partition and double-faced walls that combine glazed units with other products.

The small ledge created by Astra-Glaze-SW+ blocks combined with other products is actually very attractive. When the mason lays the walls so that the glazed surface protrudes very slightly beyond the CMU above, it can actually enhance the overall appearance.

An alternative option is to use a 2″ glazed unit and a standard-weight block backup. This enables the mason to maintain the same depth of material if desired (see Depth Alignment) and guards against moisture retention in the lightweight Astra-Glaze-SW+ block substrate.

PLEASE NOTE: A matching manufacturer approved water repellant mortar additive must be added to the mortar and built into the adjoining blocks in all such exterior applications of Astra-Glaze-SW+ units.