WATERTITE ADVICE - CONCRETE MASONRY UNIT BLOCK WALLS

Transcription

1 Waterproofing & Construction Products Since 1974 Volume 2, Issue 3 - Concrete Masonry Unit Block Walls NEWSLETTER Bentonite WATERTITE ADVICE - CONCRETE MASONRY UNIT BLOCK WALLS Tired of waterproofing delays because of the weather? Want a labour and materials system warranty? Do you need a waterproofing membrane that is self healing, can be applied in any weather and can be easily joined and detailed at transitions and difficult penetrations? When a whole lot depends on a reliable bentonite seal... Specify VOLCLAY SWELLTITE! This months feature: Concrete Masonry Unit Block Walls Swelltite applied to: Whangaparaoa College Performing Arts Centre. Contractor: Watts & Hughes Ltd. Applicator: Certified Concrete Repairs Ltd.

2 Volclay Bentonite The material and its applications Sodium bentonite is a non-toxic mineral found primarily in British Columbia, Alberta, Saskatchewan, Manitoba and the Black Hills region of the United States. It consists largely of a plastic-type clay known for its absorption, expansion, cohesion and sealing characteristics. When hydrated in an unconfined condition, sodium bentonite swells 10 to 15 times its dry volume. However, when constrained against the below-grade foundation s exterior, the material s swell capacity is restricted, and it transforms into a thick, water-impermeable gel. Most manufacturers also add polymers and other chemicals to processed bentonite, enhancing its resistance to salts and other contaminants. These additives can enhance the mineral s impermeability a hundredfold. Over the last 25 years, Volclay bentonite has been combined with geomembranes and geotextiles, forming composite products with greater performance, durability and economy. Today, it is increasingly being used on backfilled foundation walls, plaza decks, earth covered roofs and tunnels. Volclay Swelltite The material and its applications Volclay Swelltite is a highly effective waterproofing composite of 5% butyl rubber and 95% sodium bentonite compound integrally bonded to a HDPE geomembrane liner. This composition combines the active waterproofing benefits of sodium bentonite with the strength and puncture resistance of a flexible self healing rubber bentonite compound and a geomembrane liner. Volclay Swelltite is a true advancement in waterproofing membrane technology. Unlike other membrane systems which require near-perfect installation, Swelltite s active bentonite compound can expand to seal installation imperfections or small punctures in the membrane. Swelltite is manufactured at a factory controlled thickness of 2.3mm assuring the specifier, contractor and owner of consistent material application. This engineered composite consists of a white (heat reflective) HDPE geomembrane liner and bentonite compound with a clear release film attached. Swelltite contains virtually zero Volatile Organic Compounds (VOCs), can be installed in almost any weather conditions to green concrete, and most importantly, has proven effective for more than 25 years. APPLICATIONS Volclay Swelltite is designed for below-grade vertical and horizontal structural foundation surfaces, as well as above grade split-slab construction. Typical below-grade applications include backfilled concrete walls, masonry block walls, earth-covered roofs, and tunnels. Typical above grade split-slab construction applications include plaza decks, parking decks, and concrete or earth covered roofs. Applications may include structures under continuous or intermittent hydrostatic pressure. Photo courtesy CETCO When hydrated, bentonite expands and conforms to penetrations and irregular surfaces, sealing small concrete cracks. Concrete Masonry Unit Block Walls Below-Grade This article was prepared to familiarise the architect, engineer, designer or contractor with practical approaches to waterproofing below-grade concrete masonry block walls. Concrete masonry block walls have become the structural wall of choice for many architects and owners who build high-end quality residential projects as well as shallow one or two storey subterranean parking basements that can be constructed, waterproofed and backfilled with soil, scoria, gravel or low strength cement slurry. Concrete Masonry Units (CMU) are characterised by having a prefabricated concrete structure with shallow core holes that comprise approximately 45% of the block surface area. There are load bearing and non load bearing blocks. For the purposes of this article, waterproofing of load bearing hollow unit CMU blocks will be presented. CMU block walls typically contain the following components: Structural concrete footing, preferably spread footing for ease of detailing. Hollow unit CMU blocks. Mortar with proper additives such as FBS Bond R and a typical slump of 90 to 100. Reinforcing steel rebar and accessories. Properly mixed cementitious grout to fill in the CMU block hollow cores. Control or expansion joints as required. Ties, flashing accessories and notably mortar is more water permeable than CMU block work so it is critical to apply the mortar properly in the block joints and control the shrinkage of the mortar during drying. KIM crystalline concrete waterproofing may be added to the mortar to assist with this, especially for CMU block walls above grade. The mortar to CMU block bond is critical to ensure a watertight and structurally compliant CMU block wall.

3 How to Waterproof CMU Block Walls CMU block walls can be used in a number of below-grade structures including, but not limited to, the following areas: Site retaining walls that will be constructed for retaining earth of back-filled walls. Lift pits, sumps or sewage pits. Basement walls for parking. Basement walls for living spaces. Backfilled structural walls. Plaza deck planters. A summary of different waterproofing choices for belowgrade CMU block walls is provided in Table 1. This table summarises the most common commercially available systems for waterproofing below-grade CMU block walls. The long-term performance of any of the above mentioned waterproofing products depends upon the project design basis (i.e. is it hydrostatic or non-hydrostatic conditions?) Remember, most basements will be subjected to a hydrostatic condition at some stage in their life so membranes that only provide damp proofing should not be considered. How well the substrate of the CMU block wall is prepared, weather conditions during waterproofing installation, the quality of the protection source or drainage system placed on top of the waterproofing membrane and lastly the composition and installation of the backfill materials are all factors in selection. Swelltite features many advantages to the specifier and the contractor: Can be applied to green concrete as 28 day cure is not required. Self healing. Can be nailed to concrete. Can be easily joined at difficult joints. No protection required if backfill is less than 20mm in diameter average size. Can be applied in inclement weather. Not affected by below-zero temperatures. 50mm lap at joints. Roll size 1m wide x 11.6m long. Made up of white geomembranes with 5% Butyl Rubber and 95% sodium bentonite mix applied to geomembrane. Meets the New Zealand Building Code durability requirement of 50 years and is the only bentonite system in NZ that holds the BRANZ certificate. The inside of a very poorly waterproofed CMU block wall in a subterranean parking basement. Note the substantial staining and efflorescence and pitting of exposed CMU block. Table 1: Common Choices Pre-Fabricated Drainage Board (PFDB) - There are some instances where drain-board only is utilised as a stand-alone waterproofing system. Many industry experts caution using this approach because the drain-board is a water shedding system and may not always provide a waterproofing seal to the below-grade CMU wall surface. Cementitious Coating (CC) - Cementitious coatings can be applied on the positive side of the CMU wall, but are more commonly applied on the inside or negative side of the walls. This works well with integrating with a waterproofing system on the outside of the wall. Fluid Applied Membrane (FAM) - FAMs are traditionally the most common waterproofing system applied to CMU walls. The FAMs are typically one of the following: urethane (one or two part), polymer-modified asphalt (one or two part), latex-based rubber, hot rubberised asphalt, cold rubber, polyurethane, polyurea and polycarbonate. The FAM can be applied via spray, roller, squeegee or trowel. The FAM typically requires a protection course, and again is a passive technology that will not seal up pinholes, punctures or tears. The installed quality of the FAM is very applicator-specific, as experience in substrate preparation and applying the material is critical for long-term performance, and has restricted application in cold temperatures. Self-Adhered Sheet Membrane (SASM) and Torch On Membrane - Most SASMs are made up of rubberised asphalt polymer systems that contain an integral adhesive system that will help stick in intimate contact with the CMU block wall. Typically a primer is needed for effective substrate bonding and these membranes cannot be placed to green concrete footings. As the name implies, Torch On Membranes are torched on the CMU walls with an LPG flame torch. These membranes cannot be torched to green concrete blocks or footings and require a clean, dry substrate. Torch On Membranes have a wide range of manufacturers and quality. Swelltite Bentonite Composite Membrane (BCM) - This membrane includes an integral waterproofing system containing bentonite and butyl rubber adhered to a polyethylene membrane. These membranes are installed onto the CMU block with the bentonite layer in direct contact with the wall. The Swelltite systems can be adhered using adhesives/primer, and/or mechanically attached since Swelltite will swell and seal around penetrations. Seaming is completed using a simple overlap with Seamtape attached to the HDPE side of the membrane. Swelltite is hydrocarbon and contaminate resistant. Bentonite Polymer Alloy (BPA) - Volclay Ultraseal - This membrane is specially manufactured with an integrated bentonite polymer alloy (BPA) waterproofing core adhered to a polyethylene carrier membrane. The BPA is comprised of a unique formulation of bentonite and super absorbent polymer (SAP) chemically bonded together to create a lightweight active waterproofing membrane. The BPA core is installed directly onto the CMU block wall with the HDPE carrier membrane facing out. Seaming is completed using a simple overlap with Seamtape attached to the PE side of the membrane. Ultraseal is hydrocarbon and contaminate resistant.

4 Design, Installation and Quality Assurance Hydrostatic versus Non-Hydrostatic conditions: Early during design development, the engineer or architect should determine whether the basement foundation will be within, or anticipated to be within, the water table or hydrostatic conditions. Most basements, even those perceived to be in dry areas, will be subjected to hydrostatic pressure, especially during downpours when water cannot drain away fast enough or from blocked drains. One metre of water on a wall is equivalent to one tonne of force per square cm (making damp-proofing membranes unsuitable). If a hydrostatic condition is present or anticipated, then a full enveloping system should be utilised in the structure. There have been instances in the past were CMU block walls have been substituted for precast panels because of the perception that the CMU walls cannot be as strong as precast walls. Nevertheless, if hydrostatic, the designer must design an integrated underslab and wall waterproofing system (i.e. fully tanked). With Volclay, a single manufacturer system with a systems and labour warranty is available from slab to termination at ground level. If the conditions are determined to be non-hydrostatic, then the designer should design an engineered drainage system such as Aquadrain in order to manage water percolating down and around the wall foundation. This type of engineered drainage system may consist of one or a combination of the following two options: A granular drainage wedge of permeable gravel or scoria placed adjacent to the waterproofing system. The collected water that percolates through this wedge should be collected and drained through a drainage management pipe. Prefabricated drainage composite Aquadrain can be placed next to the waterproofing and into an integrated prefabricated base drain that collects the water. This can either be a drainage pipe with a filter sock or an Aquadrain base drain and connectors. CMU Block Wall Surface and Footing Preparation Surface preparation is critical to the long-term performance of any waterproofing system. Some waterproofing membranes are more forgiving than others, however most require dry surfaces free from dirt or clay and require the mortar to be cured for the full 28 days. This is not the case for Swelltite. Swelltite may be applied to damp walls and walls that may have dirt or clay from slips which can be hosed down or broomed off with a yard broom and Swelltite applied. No primers are required and due to bentonite s self-healing properties, Swelltite can be nailed into place. ST-206MB illustrates a typical wall to footing installation of the Swelltite waterproofing system in hydrostatic conditions. The critical cold pour joint is treated with Volclay Waterstop-Rx and then Volclay Bentoseal. FOUNDATION WALL DETAIL ST 206MB Masonry Block Wall - Hydrostatic FOUNDATION WALL DETAIL ST-202 Masonry Block Wall - Non-Hydrostatic Installing Swelltite composite membrane with integrated Aquadrain ST- 202 illustrates a typical wall to footing installation of the Swelltite waterproofing system in Non-Hydrostatic conditions

5 Dissimilar Structural Wall Transitions Many below-grade foundations and walls have a combination of structural walls such as backfilled CMU block walls tied to precast panels or cast in place blindside walls. How does one design and install a watertight system around these multiple wall systems? First, is the structural connection between the walls dowelled together with starter bars or stitch joints or are they designed to move? If a moving joint is required, then a watertight expansion joint must be constructed before the waterproofing is applied on the positive side of the joint. Consult Allco concerning the range of elastoproof expansion joints. Typically, the leading flap (usually 450mm wide) of the blindside precast or cast in place wall membrane will overlap the CMU block wall and then the CMU wall membrane will overlap the blindside wall membrane. Volclay meets this challenge by offering a system approach that eliminates the use of dissimilar membranes removing different manufacturers that may compromise the overall system warranty. ST-218A Precast Panel to Masonry Blockwork Pipe, services and duct work penetrations: There are many different types of pipes that will penetrate through the foundation slab including storm water, sprinkler, wastewater pipes, gas pipes, electrical conduits and air conditioning ducts that can be round or square. The penetrations can be single, multiple, or possibly ganged together. Single pipes can also be installed to sleeves specially drilled into the CMU block wall. Another option is to box out the area where the pipe, duct or gangs are located. Rx-108 illustrates this penetration block out approach. D-111B Insitu/Panel Joint Detail Rx-108 Slab Penetration Swelltite being installed, note the wet wall and footing. Installation continues regardless.

6 Termination and Tie In to Above- Grade Architectural Finish Waterproofing membranes must terminate properly at the top of the wall. With Volclay Swelltite the termination can be as simple as a counter flash or mastic over the termination bar to a Volclay Cetcoat detail. See M-114S. Below-grade termination at ground level is often a no-mans land and Cetcoat is used to detail this area where paint or plaster is used over the CMU block wall. Cetcoat prevents water wicking up the wall behind the architectural finish eliminating flaking problems at a later date. Cetcoat is typically used around gardens, stairs and planters. Cetcoat is manufactured by Volclay. What if the contractor requires the wall waterproofing to be installed in phases or lifts and not always to the final termination point? This author has experienced a number of projects where the leading edge of many different brands of membrane have been damaged beyond repair because the membrane was not covered or backfilled and was left exposed to sunlight, bad weather and site abuse. Volclay applicators will typically use Seamtape on Swelltite and in some cases place temporary protection boards over the Swelltite membrane and demand that the contractor backfill up to the bottom of this transition. Backfill Installation Gravel material has excellent compaction properties; however, it can also become an enlarged drainage collection system, which may not be desirable for some projects. Aquadrain is a good alternative that provides controlled drainage and water removal while providing a protection course to the membrane. Site soil or clay can be compacted directly against Aquadrain. If gravel is selected, care has to be taken to select a gravel 20mm or under. Angular gravel is not recommended. If gravel over 20mm is used and Aquadrian is not, it is recommended to place a protection course over the membrane. Some of the most popular protection courses include Coreflute (as used for real estate signage), polystyrene or cement board. If Aquadrain is specified, soil or clay can be utilised. Soil should be screened to eliminate large rocks and compacted in 300mm lifts to a minimum 85% Modified Proctor Density with a hand or plate compactor. Aquadrain is manufactured by Volclay Aquadrain Drainage M-114S Ground level termination Final Remarks Swelltite/Cetcoat Stair Termination Detailing Properly waterproofing a below-grade CMU block wall takes a systematic approach from the design team, CMU block contractor, waterproofing applicator and backfilling contractor. Allco can provide a specification in MasterSpec 4131AL or Volclay format with drawing details and site documents including site quality assurance manuals. This approach will ensure the property owner gets a watertight building, instead of the opposite consequence: Water intrusion, efflorescence and worse yet, a lot of wasted time and money chasing leaks. Swelltite, the problem activates the solution

7 Project Profile - Michael Hill Clubhouse at the Hills, Arrowtown Swelltite Versatility - Extends to Plaza Decks and Earth Covered Roofs Project Architect: Architects Patterson Engineer: Tyndall and Hanham Ltd Construction Company: RBJ Ltd Applicator: Adhesion Sealing (2007) Ltd Earth covering, bone dry roof and walls Aquadrain being applied over Swelltite The self-healing properties of Swelltite enable penetrations through the membrane Swelltite applied to roof with Aquadrain and earth roof topping in progress Wall and roof section of Clubhouse at the Hills backfilled walls and earth roof. Aquadrain used on walls and roof to manage water on the structure.

8 Plaza decks a ticking time bomb? Tired of leaking plaza decks and water tracking headaches? Ask for Volume 2 - Issue 2 - Plaza Decks Reference 4131AL Free Specification Service Approved Applicators On Site Quality Assurance Independent Inspection Available See Our Website 5 Airborne Road, Albany, Auckland l PO Box , North Shore City 0745 Ph l Fax l info@allco.co.nz l