B etter buildings Toronto, Ontario CASE STUDY NUMBER 30 balcony repair and retrofit Overview A detailed inspection survey conducted in October 1999 confirmed that repairs were needed on most of the balconies at a twenty seven year old, sixstorey, 84-suite condominium building in Toronto. T he balcony railings, the concrete curbs that held the balcony glass panels and the brick walls presented a potential hazard, should any loose brick or concrete fall. Glass panel frames had deteriorated, and caulking had started to fail, resulting in loose panels and a potentially dangerous situation for those using the balconies and for people and property below. A thin top layer of cementious material, previously installed, had debonded on a majority of the balconies. As well, repairs to the sixth floor balcony knee walls had failed, with delamination occurring. Corrosion of underlying reinforcing steel proved to be the cause of this. The condominium s Board of Directors and property management agreed to undertake repair work to improve the balcony area of each suite. The work was performed as a preventive measure and to address growing concerns about the debonding of the top layer of the balcony slab. The main objective was to ensure each unit had a safe, comfortable and aesthetically satisfying place where residents could enjoy the outdoors. In addition to the required repair work, cosmetic repairs proved necessary to meet this objective. View of the project In general, the work involved the following tasks: removing permanent carpeting and tiles, which had accelerated deterioration of the concrete flooring; repairing reinforcing bars and concrete on the floors;
improving drainage by re-leveling floors towards the drains and improving spigot length; caulking wall joints; repairing delaminated concrete curbs that held the balcony glass and railings; repairing the U-channel framing and re-caulking around the frames to hold the glass panels in place; replacing spalling brick at the shear balcony walls; repairing the concrete roof top canopy; and improving existing drainage. Initially, balcony floors were repaired with patches, but the patches were considered visually unacceptable. Many residents complained, but no further repairs were scheduled. Residents had also been advised that floor covering of any type was not an option and no furniture or balcony décor was allowed. While the purpose of this work was to prolong the life of the concrete repair and existing concrete floor slab, it ran counter to the intended purpose of having a balcony, and prohibiting any seasonal furniture or other décor was not acceptable. The engineering firm determined that the only option was to place a waterproofing membrane on top of the balcony floor slab. The Board of Directors agreed with this, and a waterproofing membrane was contracted as additional work. All major structural repairs were addressed first, before the cosmetic repairs.work commenced in September 2000, and the original work contracted was completed in the spring of 2001, with a winter shutdown from December to April. The additional work of installing waterproofing membrane was done from April through August 2001. The project Work performed Work on the concrete balconies involved the following procedures: Remove and dispose of all carpet, wood flooring and ceramic tiles on balcony slab and walls. Water-blast, mechanically grind and/or chemically clean the top surface of the balcony slabs and parapet railing wall to remove all debris, such as carpet cement and tile grout. Condition of balconies prior to repair Inspect, sound test and mark all delaminated concrete areas on balcony edges. Sound testing consisted of hammer testing for hollow-sounding concrete. Saw cut, break, remove and dispose of delaminated concrete on balcony front edge, balcony side wall and front slab edge for hand patch repairs with trowel. Sandblast all repair surfaces of concrete, reinforcing steel and handrails anchors and coat steel. Repair balcony front edge and balcony side wall delamination. Replace deteriorated reinforcing steel with epoxy coated reinforcing steel bars. Repair balcony edge slab delamination on exposed sides.
Ensure or provide sufficient slope on top of balcony slab so that water flows from the building to the drainage pipe at edge of balcony. Remove all delaminated concrete balcony soffit spalls, sandblast and clean repair area. Remove all damaged caulking from the joint between the balcony floor slab and wall, clean area and reapply new caulking. Paint balcony soffit with two coats of exterior enamel paint. Paint main entrance canopy. Brickwork repairs involved removing, disposing of and replacing spalled or cracked bricks, and cutting out and repointing all cracked, debonded and open mortar joints. Although the balcony railings did not meet the current 1997 Ontario Building Code, they were found to be solidly anchored and still in compliance with the 1970 Code, which was in effect when the building was constructed in 1971-72. The 1997 OBC requires measures to deter climbing.the existing concrete curb can allow for some climbing.all in all, the railings did not require removal or any major modifications. They only needed to have their fasteners re-secured and, in some cases, minor welding repairs. Panel frames required some repair, due to rusting, especially in the bottom channels, and caulking needed to be replaced. General repairs to the railings involved removing the glass panels, and sandblasting, wire brushing and grinding all metal surfaces. U-channel support bars were replaced with new galvanized steel where necessary, and the railings were then primed and painted. Finally, balcony slabs were waterproofed following these steps: Grind or light sandblast concrete surface to remove all paint and glue. Prepare and seal tops of slab cracks with elastomeric coating, or rout and seal with sealant as specified by manufacturer for waterproofing material. Resurface balconies that do not completely drain water from the building to the drainage area.
Waterproof balcony slabs using an elastomeric waterproof deck system suitable for pedestrian and light-duty traffic. The balconies were resurfaced using a polymer modified cementious mortar. The product was chosen for its fast-setting and corrosion inhibitor properties. Installation requirements stipulate that after sand- or waterblasting the surface, and prior to applying the mortar, the surface must be saturated with clean water, and once the mortar has been The finished product Installation of waterproofing membrane applied, it should be cured with mist or damp burlap for 24 hours. The waterproof system was a liquid-applied polyurethane elastomeric waterproofing membrane and a liquid-applied aliphatic urethane elastomer combined with silica sand for the wear-coat. Although elastomeric waterproofing systems have been in use for some time, using this type of membrane material on balconies was a relatively new application, with little history about its performance in such locations. Key factors contributing to success The Board of Directors played a key role in keeping repair work to a minimum. Any questionable repair or modification was reviewed in detail and either removed from the original specification or treated as an extra if required. The engineering firm and property management insisted on bimonthly construction meetings with the restoration company to obtain progress reports and address any concerns. This also enabled management to keep residents up to date on a bimonthly basis, which reduced the number of telephone inquiries and disruptions. Difficulties encountered The project did not start early enough in the season to avoid shut down during the winter, and some residents could not use their balcony over the winter months. Although work was scheduled to minimize disruption, residents complained about the noise during construction. Also, residents were not informed as to what to expect with regard to the concrete patches, which proved to be aesthetically very unappealing. As a result, many complaints followed this repair work. At the time, no further repairs were scheduled. To add to this, residents were advised not to use any type of floor covering or place other décor or furniture on their balconies.
The recommendation to waterproof the floor slabs solved both the aesthetic and functional problems. In the end, residents were pleased with the finished product which provided a uniform finish as opposed to a patchwork appearance. Residents must still be careful about the type of flooring and furniture they put on their balconies. To prevent problems, they are required to submit a written request to the Board for approval before placing any flooring or other items on their balcony. They have also been advised to use non-abrasive support brackets on the metal balcony railings. The cost The total cost for the project was $223,450 plus GST, with engineering fees being six per cent of the cost for developing the scope of the work and preparing bid documents. The work originally contracted cost $153,000 plus GST, and the balance of $70,450 plus GST covered the additional work involving improved sloping for drainage and waterproofing. All costs were covered by funds from the condominium's capital replacement reserve fund. Conclusion The repair work has extended the life of the balconies and made them aesthetically attractive, thus enhancing the marketability of the suites. Both property management and the Board gained a better understanding of the importance of balcony slopes and waterproof coatings. As such coatings require maintenance, access to each suite is required on an ongoing basis for periodic inspection, cleaning and any future repairs to the coating due to scratches or tears in the membrane. Project team Property Manager: Glenn Luckasvitch, RCM, Brookfield Property Management gluckasavitch@brookfield.ca Consultants: H. Rentsch Associates Ltd.; Cedaridge Research Ltd. Rob_Marshall@rjburnside.com Restoration Company: Brooks Restoration If you have any comments, or would like to submit your project for publication, please contact: ldemigue@cmhc-schl.gc.ca For more information about building envelopes solutions and best practices, visit the Canada Mortgage and Housing Corporation (CMHC) Web site at: www.cmhc-schl.gc.ca and visit the Highrise and Multiples Web site at www.cmhc-schl.gc.ca/ research/highrise/