Menu of problems we’ve tackled and resolved
Engineering Department
QA Department
Engineering Department
Better Formwork System - South Health Campus – There was a high cost for the forming system for this Phase 1 $900M project. The Engineering Department approached all of the larger formwork suppliers to devise a better formwork system than the current conventional systems, in order to find the best forming system possible, including the elimination of reshoring (a schedule impediment). With extensive collaboration with EllisDon’s Engineering department, Peri Formwork Systems responded with a new hydraulic automatic self-cambering system called IntElliDeck (CMS -- column mounted system), a system that was used for the first time in the world at the South Health Campus project. Formwork Analysis of Total Costs (including assembly / cycling / dismantling labour costs / material costs and craneage costs) for this project show this system to be less expensive than other formwork systems by up to $10M.
Mobile Crane Insertion - Roy Thomson Hall Renovations – In order to construct the new volume reduction bulkheads and acoustical canopies renovations work, we decided a mobile crane was required inside the Main Auditorium for construction during Roy Thomson Hall’s 22-week Dark Period. The appropriate mobile crane was chosen, a 22-ton Grove mobile crane, based on the capacity required and the crane’s geometry. We needed to get the mobile crane in through an existing loading dock (6’-8” x 6’-8” approximately) and through corridors with as little turns as possible. In some spots, there was ¼” height clearance. AutoCAD drawings were created to determine the best route (the drawings contained accurate mobile crane specs and the building specs). The mobile crane was dismantled, including torch cutting of the outriggers, in order to be moved inside. Due to the tight fits through the doors and corridors, the crane was mounted on its side on a skid and then pulled behind a bobcat and come-along. It was then reassembled inside the Auditorium with the assistance of smaller Broderson mini cranes. The crane exhaust was piped into an exhaust shaft to keep the air inside the Hall suitable for tradesmen. The mobile crane was removed the same way.
Hinged Forming Platform – Our Engineering Department has devised a new and safer hinged forming platform. On all of our self-performing formwork projects, we use the new stair/elevator hinge platform. This new system allows the platform to be raised by disengaging and resetting at a higher elevation by crane only, without the requirement of having a worker inside the shaft.
R&D Department
Floor Flatness – Issues with floor flatness (FF) occur when concrete slabs do not meet the tolerances set out in the concrete specification. Typically in the past, tolerances were based on using the traditional 10’ straightedge method, which is not reliable and not repeatable. The F number system is a state-of-the-art way of measuring flatness and levelness, which is statistically valid and is repeatable. Now, the industry standard is to use the F number system. Over the past years, EllisDon R&D Department has educated both project staff and subcontractors about this more reliable method. The R&D staff typically goes out to sites and takes F measurements on randomly picked slabs. If it does not meet the specifications, we meet with all involved parties to help implement changes in order to achieve the required tolerances. After subsequent pours, more measurements are taken and if required, more changes initiated. This process keeps occurring until the required tolerances are met.
Floor flatness is a huge issue industry wide. If tolerances are not achieved, subsequent costly remedial work involving cutting and patching will have impacts to scheduling and budgets.
Moisture Vapour Transmission – this is an industry-wide problem. Problems occur when moisture-sensitive flooring is used when there is a high moisture vapour transmission rate through the base concrete slab. Suspended slabs with finished flooring are generally not affected. There are 2 main sources of moisture in concrete that can pose a problem: sub-slab moisture vapour (which diffuses through the concrete), and residual water in the concrete mix which is meant to dry over a required period of time.
- Vapour Retarder for SOG -- Why has moisture vapour become a problem in recent years? Adhesives used in the past were solvent based and not environmentally friendly, but strong enough so the adhesives did not break down in the presence of moisture. Now, adhesives are water based and environmentally friendly, but are affected by moisture and are breaking down, thus causing damage to moisture sensitive flooring (buckling, lifting, etc). R&D reviews our projects’ concrete specifications to ensure a suitable/durable vapour retarder is specified. We follow state-of-the-art technology/techniques recommended by the technical committees of ACI, CSA, PCA, etc. R&D continually educates Owners, Architects, Subcontractors, Suppliers, etc., about this issue and solutions, who then take this knowledge to other projects.
- Concrete RH -- The traditional method of measuring concrete moisture was with calcium chloride testing, which is still being used today, but is not accurate and is highly influenced by the surrounding ambient conditions. EllisDon R&D is using RH (relative humidity) measuring probes (state-of-the-art technology) which give a truer indication of what moisture levels will be after the flooring is installed. It is very important to have continued monitoring processes in place and collect the data for future use, which we are doing. If the desired RH level is not reached, it means delay in laying down the adhesive and floor on the SOG. A relative humidity of below 75% is required (or as per the flooring manufacturer’s recommendations), and should be reached before continuing with finishes on top of the SOG. Concrete drying time is highly variable and is dependent upon such things as the thickness of the SOG, water/cement ratio of the concrete, ambient conditions, etc. Solutions include bringing in external heaters and dehumidifiers to draw the moisture out. Alternately and/or additionally, if it is possible, schedule work to start on the top suspended slabs and do the SOG last to allow for extra drying time (can gain up to 3-4 months extra to allow the SOG to reach the required RH). The ultimate goal is to have the SOG sufficiently dried so it does not affect the finished floor.
Curtain Wall / Windows – There is an industry-wide building envelope problem with regards to leaks, specifically at the transitional interfaces between different exterior wall systems. The EllisDon R&D Department continues to be proactive in their review of project specifications and shop drawings, as well as actual installation (interfacing details, etc.). If any of the details areas are lacking in some way, we provide recommendations to Owners, architects and the project team to how best fix it. R&D is also involved in mock-up performance testing of curtain wall systems. R&D also performs its own troubleshooting testing for the building envelope at early stages of installation (i.e. blower door smoke testing, water infiltration testing, etc.) and data collection from such testing.
Self-Consolidating Concrete – Self-Consolidating Concrete (SCC) is a new type of concrete which “is highly flowable, non-segregating and can spread into place, fill the formwork, and encapsulate the reinforcement without any mechanical consolidation.” (quoted from ACI 237 Self-Consolidating Concrete)
The benefits of SCC are:
- That less labour is needed because vibration of the concrete is not required for consolidation.
- It can accelerate the rate of construction.
- Reduction of noise.
- It creates smooth surfaces free of voids and honeycombing.
- It facilitates placement of concrete in areas heavily congested with reinforcement.
EllisDon projects where SCC has been used:
- Padgett Thomas Barracks, The Citadel, Charleston SC
- Law Barracks Replacement, The Citadel, Charleston SC
- Bloorview McMillan Children’s Hospital, Toronto ON
- Bay Adelaide Centre, Toronto ON
- Peterborough Regional Health Centre, Peterborough ON
- Ritz-Carlton Simcoe Centre, Toronto ON
- Labatt’s Expo, London ON
- MaRS ‘C’ Building
- 180 Queen Street West Office Building
- Toronto Centre for Phenogenomics
- Art Gallery of Ontario
- Other ED Ontario projects
The EllisDon pilot project for SCC was the Padgett Thomas Barracks at The Citadel, Charleston, South Carolina. There were strict requirements for the architectural concrete. The last Citadel project was constructed with traditional concrete and completed with a painted surface finish. There were problems in a lot of locations with voids and honeycombing, therefore a lot of rubbing and patching was required on the new Citadel project. Lloyd Keller, Director R&D/QA, and Ready Mix Concrete (concrete supplier) proposed the custom designed SCC as an alternative at a minimal premium cost. The Owner was extremely happy with the outcome. As a result, the next Citadel project (Law Barracks Replacement project) had SCC written into the concrete specifications. EllisDon was eventually awarded this Citadel project.
The EllisDon R&D Department is one of the world-wide construction industry leaders in research on self-consolidating concrete. We continually conduct ongoing field measurements and gathering of test data to determine what factors influence formwork pressure when using SCC. EllisDon is heavily involved with ACI Committee 237 (Self-Consolidating Concrete) and ACI Committee 347 (Formwork) in its ongoing research of this product.
QA Department - Learned Lessons & Continuous Improvement
We at EllisDon clearly understand the fact that measurement is an essential step towards improvement. Our focus is to seek out potential problems as early as possible, investigate their extent, take corrective actions and ensure that preventative measures against recurrences are taken. Here are some real examples on how we improved based on learned lessons:
Concrete Surface Finishes: Over three years ago, as a consequence of low results on the quality of the flatness of concrete surfaces in some of our projects and in the construction industry in general, EllisDon, through its Quality Assurance Program, initiated a process to increase awareness and improve performance. At that time, most of the project specifications described the straightedge method as criteria to verify conformance. The straightedge method is not repeatable, therefore not reliable. We have, since then, been pushing for the implementation of tolerance measurements based on the Floor Flatness (FF) number method. At the Peterborough Regional Health Centre project in Ontario, the Subcontractor did not achieve the required FF number of 30 in the first placement. Through a joint effort between EllisDon, the Subcontractor and Concrete Supplier, procedures were modified and plastic properties of concrete mix such as slump and setting time were adjusted. As a result, the FF number was achieved for all subsequent areas of the work. The same procedures and results were achieved in other projects such as the Art Gallery of Ontario Transformation Project, Darlington Used Dry Fuel Storage Facility and the 6775 Financial Drive Project, among others.
Bentonite Waterproofing System: Problems with the installation of bentonite waterproofing resulted in leakages at an EllisDon project. In addition to having this deficiency fixed at this project, EllisDon in conjunction with the subcontractor, developed a quality control program to prevent reoccurrence of the same problems in subsequent projects. A visible improvement on the installation work was then achieved as a direct result of the involvement of the subcontractor and our project team on the planning and implementation of QA/QC procedures at the Bankers Court project in Calgary. These procedures included the development of a project specific Quality Control Plan, technical review of the project specifications and construction details, identification step by step of the installation procedures, mock-up installation and approval, sequential inspection and sign off by the subcontractor and EllisDon of the completed areas of the work. The same procedures were then implemented, and the same level of quality was achieved, at the Jamieson Place project in Calgary.
EllisDon Construction Consulting
How to Get Started
For more information on EllisDon's Engineering, Research and Development and Quality Assurance Services, please contact Steve Seifert, Senior Vice President, Engineering/Research and Development.
Case Study
Moisture Vapour Emission (PDF, 199KB)Successful Projects include:
Bay Adelaide Centre
Rogers Centre
Eighth Avenue Place
AGO - Transformation
George Brown College Waterfront Health Sciences Campus
South Health Campus
First Canadian Place
CORE Shopping Centre
Industry Memberships
- Professional Engineers of Ontario (PEO)
- Ontario Society of Professional Engineers (OSPE)
- Association of Professional Engineers, Geologists, and Geophysicists of Alberta (APEGGA)
- American Concrete Institute (ACI)
- American Institute of Steel Construction Inc (AISC)
- Canadian Standards Association (CSA)
- Ontario Building Envelope Council (OBEC)
© EllisDon Corporation 2010
