Panelized and composite stone masonry

by sadia_badhon | November 28, 2019 11:21 am

By Ralph Bruno

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Builders and designers are now continuously looking for the rich mixed material esthetic natural stone offers. However, it is not always possible to achieve it because skilled labour might be unavailable. Construction professionals may therefore seek products requiring less inherent skills. Thankfully, newer technologies can reduce concerns about installation and weather challenges with traditional stone materials. Specifically, the market is seeing solutions, such as manufactured/cultured stone, panelized manufactured stone, and composite stone. Composite stone alternatives represent an emerging category, as they are easier to install and maintain and have the added benefits of moisture impermeability and colourfastness.

All masonry products have their pros and cons, depending on the project, timeline, and what the installer hopes to achieve. Composite stone panels are lightweight and, therefore, do not require heavy equipment or jobsite tenting during installation to account for inclement weather conditions. They strongly resemble stone veneer and come in 2-m (6-ft) panels. Mortar looks are available, but mortar or grout is not needed for installation. The panels do not contain silica. A grit texture is applied for a realistic matte finish and feel.

Panelized stone veneers can be installed by almost any siding contractor or carpenter as they can be cut with regular woodworking tools. Stone veneer systems with built-in clips are also mortar-less, but use a wire hanging system. While not necessarily panels, they can cover larger areas than typical veneer sizes. For panelized stone with preassembled veneers, safety equipment to protect from silica is recommended, though the panelized and clip systems require less cutting.

Masonry stone installation

As mentioned, stone installations require skilled tradespeople who are familiar with a range of tools and building products. In most installation scenarios, a mason requires specialized wet saws, scaffolding, bracing/supports, and mortar/grout mixes to install heavy natural stone or cementitious veneers. The Canadian Centre for Occupational Health and Services’ (CCOHS’s) jobsite safety regulations are similar to ones by the Occupational Safety and Health Administration (OSHA) in the United States, although Canadian requirements are governed by provincial occupational health and safety legislation. Prudent safety measures require masons to establish a limited access zone, tie-offs, scaffolding, and supporting elements. These may limit mobility on the jobsite.

As regulations tighten and skilled labour becomes more difficult to find, designers have sought building techniques requiring less work, while maintaining an esthetic appeal[2] resembling natural stone.

As explained earlier, manufacturers have addressed labour shortage by creating products offering the appearance of stone but with a significantly easier installation process and built-in moisture management. New composite stones are lighter than traditional cement-based options, they are suitable for ground contact, deliver moisture resistance, and are silica-free. Composite stone products reduce the need for layers of mortar coatings, metal screens, and moisture barriers. Additionally, they eliminate the requirement of time-consuming code inspections. Composite stone delivers the desired look, feel, and overall esthetic.

Stone veneer systems have been developed in both panelized systems and/or with integral wire hanging attachments to reduce cuts, ease installation, and assist in moisture management, while eliminating the need for mortar. Stone veneer systems with built-in clips do not require cold weather preparations like a rainscreen, but need a weatherproof barrier.

While composite stone and panelized veneer products have removed the mess of mortar/grout from the installation process, this is not the case for all stone options. Additionally, cement-based stone veneer components often require presorting of the colour patterns, need specialized cutting equipment, and proper ventilation due to silica dust, a known carcinogen. Silica dust is flagged[3] by both CCOHS and OSHA as a health hazard with exposure leading to a variety of ailments including silicosis. Craftspeople cutting stone, stone veneer, or panelized manufactured stone veneer should work with caution in a well-ventilated area, as some products contain up to 50 per cent silica.

As with other occupational regulations, silica exposure levels in Canada’s construction industry vary by province. An alarming report by CAREX Canada[4] cites that approximately 380,000 Canadians are exposed to silica at their work, primarily in the construction sector. According to the 2011 cancer statistics from the Occupational Cancer Research Centre’s (OCRC’s) Burden of Occupational Cancer Study, 570 lung cancer cases (2.4 per cent overall) were attributed to the occupational exposure to crystalline silica in Canada.

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Types of masonry products

There are many types of masonry products available in the market.

Stone

Natural stone requires a high level of skilled labour and mortar layers/grout. Building professionals must consider several factors when installing stone such as:

• gypsum layer, batt, and wood frame;
• dry times for mortar scratch coats and inspections;
• weep screens and screeds required for drainage;
• moisture is a consideration requiring engineering behind the wall;
• cold weather mitigation is needed for installation;
• shipping weight and stocking ability; and
• safety precautions at heights.

Stone veneer (with mortar)

Stone veneer also requires skilled labour. When using stone veneer in building projects, design professionals must take into account the following:

• esthetics resemble natural stone;
• easier to mix and achieve custom colours than natural stone;
• more than half the cost of natural stone;
• gypsum layer, batt, and wood frame;
• several mortar layers, metal lath, and two water barriers;
• weep screens and screeds required;
• application of grout, dry time, and excess removal;
• moisture sensitive due to cementitious material; and
• safety precautions needed at heights.

Stone veneer (without mortar)

Stone veneer systems without mortar are primarily installed with a clip system, or with a hanging mechanical fastening method. Other aspects include:

• gypsum layer, batt, and wood frame;
• attachment of wire system and screw to wood frame;
• similar in cost to stone veneer;
• stones/small panels installed individually;
• integrated weep channel between panel and wall;
• stones can vary in size and colour (installer needs to create random pattern);
• look for carcinogenicity warnings (ventilation equipment must be worn when cutting); and
• unlikely to come loose and fall (wire is integrated into the mould woven through middle of stone).

Composite stone

Lighter weight composite stone in cladding panels cover 0.5 m² (5 sf) per panel, and offer faster wall coverage than other methods. Other features include:

• gypsum layer, batt, and wood-frame—it is recommended to apply a weather-resistive barrier (WRB) and starter strip at bottom of wall;
• offers dry stacked or grouted look;
• uses colourants and grit textures to achieve stone-like look and feel;
• single installation with interlocking panels that are mechanically fastened;
• a fraction of the cost of real stone or stone veneer;
• panels are designed to vary in colour so each will look different;
• no skilled masonry required, and any contractor can install with standard siding tools;
• no mortar, grout, or heavy equipment as well as no dry times or mid-job inspections;
• CCOHS compliant—meets silica dust requirements (no silica); and
• no risk of loose or falling stones.

Cold weather issues

When ambient temperatures drop below 4 C (40 F), cold weather construction methods for masonry must be applied to ensure structural strength and also proper moisture management. The Canadian Standards Association CAN/CSA A371-14, Masonry Construction for Buildings, and American Concrete Institute (ACI) 530.1-08/American Society of Civil Engineers (ASCE) 6-08/the Masonry Society (TMS) 602-08, The Specification for Masonry Structures, outline requirements for masonry construction in winter. During cold weather construction, water requirements in mortar are reduced to reach the desired consistency as too much liquid may freeze and cause a disruptive expansion. Additionally, the initial and final sets of mortar are significantly delayed, and strength rates are reduced.

Masons have developed a variety of strategies to mitigate issues associated with cold weather construction. Masonry materials optimized for cold performance, such as high-strength mortars and those with well-graded sands, are ideal as they require less water. Admixtures like cement accelerators can provide builders with increased rates of early stage strength development. However, such admixtures may only be used if previously specified. Only non-chloride-based accelerators are allowed by ACI 530.1-08/ASCE 6-08/TMS 602-08, as chloride contributes to corrosion[6] of embedded metal structures.

Additionally, masons may protect building materials by wrapping them in canvas or tarps to deter moisture and contaminants. In some instances, a temporary, heated, enclosed work area may be raised at the jobsite to prevent contamination and mitigate severe weather. Moreover, some masonry materials like sand and water can be warmed with heating pads, steam heating systems, or fire. Although a combination of cold weather tactics can be employed, these circuitous methods can prove costly and time consuming.

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Without the need for mortar, composite stone options are cold-weather-ready for installation. Panelized stone veneer (without mortar) also does not require heat for installation for the same reason. Both products do not need a rainscreen unlike stone and stone veneers using mortar, but require a WRB.

Moisture mitigation

For any type of masonry project, the prevention and mitigation of moisture is essential for controlling mould, mildew, and structural damage. Moisture abatement best practices include:

• flashing;
• counter flashing;
• weeps;
• vents;
• sealants;
• water repellents;
• post-applied surface treatments;
• vapour retarders;
• crack control measures; and
• a program of surface protection[8], internal protection, and drainage and drying.

Additionally, the Building Enclosure Moisture Management Institute[9] (BEMMI) of Winnipeg, Man., recommends any region receiving more than 500 mm (20 in.) of annual rainfall should incorporate enhanced drainage techniques into the wall system, especially if using an absorptive cladding material. Areas receiving 1016 mm (40 in.) or more of rainfall should utilize a weather barrier or rainscreen design, regardless of cladding material. The geographic orientation of the wall, amount of roof overhang, altitude, and even nearby trees can impact the level of water intrusion expected and how likely it is to dry. In many places, new and evolving building codes are driving the need for better moisture management solutions. For example, Canada’s wetter coastal provinces now require, per the National Building Code of Canada (NBC), wall assemblies to be built with capillary breaks between WRB and the exterior veneer.

Mortar formulations for cold weather construction can also be used to manage moisture. Adding water-repellents on the jobsite is generally considered the best method. To help reduce the effects of freeze/thaw conditions, a polymeric admixture can be used to increase adherence.

Drainage is another important consideration in moisture management. Several products now include built-in weep holes or backchannel drainage systems. Manufactured panelized stone veneer systems with built-in clips are designed to create a weep channel behind the stones for drainage. However, they still may be susceptible to efflorescence (a chalky substance created by surfacing salt) and even mould and mildew contained in the rough, porous surface of the stones, which can be difficult to clean.

Composite stone has the advantage of being impervious to moisture and efflorescence, while being highly resistant to mould. In extremely damp conditions, mould will grow on any surface. If this occurs, composite stone can be cleaned off with detergents and a hose. Designed weep holes and drainage channels are included to keep water away from the wall and allow proper ventilation.

Skilled labour issues in Canada

Along with lengthy installation times, the skilled labour shortage[10] continues in the Canadian building industry. Even with ongoing economic growth, there is a huge shortage of skilled labour in the country, notably skilled masons—who are so few and far between in many provinces—that home builders are resorting to exclude masonry or brick in building plans. This illuminates the critical need for alternative, easily obtainable products that can be installed with less skilled labour at a faster pace.

Currently, the Canadian construction industry shows overall contractors simply cannot get the job done without qualified workers.

Even with ebbs and flows in growth, the construction industry needs to recruit, train, and retain an estimated 300,000 new workers over the next decade. According to a BuildForce Canada study, hiring needs will be driven predominantly by the expected retirement[11] of more than 260,000 construction workers, or 22 per cent of the current labour force, forcing many in the industry to take a long look at employee engagement and recruitment.

On a national level, Canada is reaching out to immigrants as a skilled labour solution, with the Canadian Federal Skilled Trades Program (FSTP) offering qualified people the opportunity to become a permanent resident in an attempt to ensure the country attracts and retains a skilled workforce.

When it is impossible to employ natural stone, alternatives may be the solution to achieve the desired esthetics. Current skilled labour shortages underscore the need to find readily available, easily shipped products any contractor can install. The North American building industry is poised to respond with easier panelized and composite systems to solve a host of jobsite, performance, and labour issues.

Ralph Bruno is CEO of Derby Building Products Inc., the Québec City-based manufacturer of exterior cladding products, including shake and composite stone. A veteran of the building materials industry, Bruno was instrumental in leading the conversion from traditional materials to composites. He can be reached at rbruno@derbybp.com[12].

Source URL: https://www.constructioncanada.net/panelized-and-composite-stone-masonry/

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