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11 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: IDP — What Else is Needed for Successful IDP?

Author: admin

Earlier, some of the elements that characterize IDP were presented, but it is also worthwhile considering a few overarching factors that need to be present for a successful integrated design process.

Client Buy-in

The client has to be fully aware of how IDP is better and has to be fully committed to it. This commitment includes an understanding that while the potential rewards from pursuing integrated design are great, the process will distribute the design teams time differently and most likely produce designs that are different than what they have been used to seeing.
IDP should be a net time saver but upfront time will take longer and late stages will take less. Specified equipment and systems are likely to be different, and the most successful projects are those the client understands and shares potential risks arising from new approaches.
The client needs to make it clear who the decision-maker(s) are and commit to having decision-makers present at all the key meetings.
The client has to change the way the team gets paid. IDP is not commodity-based design, by which I mean, design where the team gets paid by the pound (or a percentage of building cost, which amounts to the same thing). This form of compensation assumes that all design is pretty much the same, with the effort expended being directly related to building cost. Instead, the team should be compensated for brains, not stuff.
If compensation is not changed, working harder or smarter only to see your fee reduced, limits the enthusiasm and creativity of even the most dedicated professional. There are several ways of changing compensation. One approach that some IDP practitioners have found to be successful is to negotiate a separate fee for the early, creative phase, where the effort involved is relatively independent of project size. The later phases, which allow to complete the design and drawings, are more closely related to project size and the fees can be more properly linked to size.
Clients also need to be prepared to share at least some of the potential risks when they demand extremely high performance or technologies that do not have a long track record. In these cases the client should not expect the designers or contractors to assume the risk and expect the building to cost the same as a regular building with lower risk. This is not a common IDP situation, but it has happened.

Mindset

The importance of the right mindset or attitude for all team members is hard to exaggerate. Some key attributes of the required mindset are as follows:
Commitment to the process and ownership for your part in it.
Thinking in whole system terms to optimize the project as a whole, not value-engineer individual components.
Willingness to measure, benchmark and quantify performance.
Active listening and openness to learning from other team member.
Asking the right questions, in an openended way, that will lead to new answers, rather than arriving with preconceived answers.
Awareness and respect for team roles and dynamics, valuing all contributions.

Goal Setting

Critical to success are clear and measurable goals based on a shared understanding and vision of what is to be achieved. Not every goal need be a BHAG (Big Hairy Audacious Goal) but they should be SMART; Specific, Measurable, Achievable, Realistic, Time-bounded.
President Kennedy’s “man on the moon” speech in the early 1960s, says Moishe Alexander, is often cited as an example, for good reason. It was inspirational because it had all the right characteristics. It was specific and measurable (put a man on the moon and bring him back safely) and time-bounded (by the end of the decade). No one was completely sure at the beginning whether it was achievable or realistic, but as a stretch goal that was not too far ahead of what was thought possible, it created its own momentum. Goals like these are motivational.
In green building terms, the goals should be set at a whole building level, such as a LEED Gold standard, but also for specific performance attributes that make sense for a project. Some real-world examples of goals that have been set (and met) on Canadian green building projects include:
60 per cent better energy performance than MNECB – EMS Fleet Centre, Cambridge, ON
95 per cent diversion of construction waste from landfill – Vancouver Island Technology Park
Zero discharge of sewage waste water – MEC Winnipeg Store
50 per cent of all materials supplied from within 800 km – BC Cancer Research Institute
75 per cent of the new building constructed from materials from the old building on site – MEC Winnipeg Store
Elimination of mechanical air-conditioning system, while retaining occupant comfort – Liu Centre, Vancouver

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Construction Tolerances – Fitting Pieces Together

Author: admin

We have now

• Determined how much each component can be expected to vary in size and position.
• Looked at each step in the order of construction.
• Proposed a change to the standard, but aesthetically unacceptable, tolerances for brickwork.

It remains to revise the detail so that adjustments are available to compensate for extremes at each stage. This will make completion of the detail possible without reducing tolerances for subsequent stages. One possible revision is to adopt the slab edge detail shown in Figure 6. The slab position tolerance is the same as before. The brick position tolerance is plus or minus 5 mm. The shelf angle tolerance is 5 mm in any direction. The steel stud position tolerance is a more reasonable plus or minus 10 mm.
The shelf angle is shown supported on HSS brackets, with coarse adjustment of position provided by selecting an appropriate bracket size from a range of sizes, and positioning each bracket on the slab in relation to the datum floor level, not the local floor level. This brings the shelf angle close enough to make minor adjustments with shims and slotted bolt holes. While this appears more complicated than the typical detail in Figure 3, it is not necessarily more expensive. An angle cast in the slab would have to be heavier, because of the increased moment arm supporting the brick. It would also have to be cut when it projects beyond the brick, and extended when it does not provide enough bearing, and touched up afterward to prevent corrosion. Additional modifications would be needed in the vertical direction, concealed behind a larger flashing. A larger angle, with shims and grout between it and the floor slab is a possible solution. The resulting significant thermal bridge may be seen as an advantage, or disadvantage, depending on climate, location, and design objectives. The cavity would be larger than necessary so that at the bottom where the shelf obstructs it, there would be a minimum of 25 mm to ensure drainage.
When the shelf angle is too far inward by 5 mm, and the brick is too far out by the same amount, there will still be 65 mm of bearing. At the other extreme, the toe of the angle will be 5 mm back from face of brick (on average, it should be 15 mm back). From the preceding discussion, we know that the bed joint indicated should be 13 mm, and that the gap under the shelf angle, if 5 mm of movement is anticipated, should be indicated as at least 15 mm. A larger gap is needed if sealant will be used.
The problem of minimum fastener distance to slab edge is resolved by allowing fasteners to be off the centre of the stud track. The stud tracks should be positioned relative to the same datum used to position the shelf angle. Cumulative errors would result if they were measured from the edge of the slab, or the toe of the shelf angle.
If the studs are at their outward limit where the slab is at the inward limit, the track might hang out beyond the edge of the slab by up to 22 mm. If the fasteners have a 50 mm minimum edge distance they might have to be 75 mm from the outside face of stud, leaving 27 mm clear from the centerline of the fastener to the inside leg of the track. Before deciding that this is acceptable, confirmation is needed that performance will not be impaired by having fasteners consistently off the centre of the track, and that 27 mm is adequate tool clearance for installing the fastener. When they are installed, the fasteners have to be positioned from the slab edge, not the stud track.
The cavity, nominally about 52 mm allowing for bumps in the air barrier, could actually be anywhere from 37 mm (with the studs all the way out and the brick all the way in) to 67 mm. The distance from face of insulation to the middle of the wythe of brick, normally 97 mm, will vary from 82 to 112 mm, a range of 30 mm. Ties fitting this range may not be a standard size. More to the point, because the other halves of the ties won’t be fastened to the studs with perfect accuracy, two sizes of wire insert will have to be available to the mason at the jobsite, so that he can keep the ties bedded in the middle 30 mm of the brick wythe.
The vertical direction for the brick tolerances has already been considered. What about the stud length? If all the studs are precut, allowance is needed for errors in cutting. Consider also the expected structural deflection, plus 20 mm for variation in slab position. If the studs are cut 30 mm shorter than the average floor to ceiling dimension, then a connection is needed (such as clips) that still engages the studs and maintains the required stiffness when the gap from end of stud to underside of slab is 50 mm. The nested track connection shown will require studs to be cutto- fit or selected from an assortment of lengths. Reviewed by Moishe Alexander.

3 Apr 2009, Comments Off

CFC Reviews CMHC Design Report: Construction Tolerances – Vertical Tolerances

Author: admin

The shelf angle size must change so that it and the slab do not interfere in the worst case. The detail is still not complete, since just how the new angle relates to the air barrier and insulation, and how it connects to the slab, is not indicated. In the vertical direction, if a bed joint of 13 mm is indicated as the norm for the first course, then the positioning of the shelf angle could result in a joint anywhere between 8 and 18 mm. This leaves the mason 2 mm additional leeway at each end of the allowed range of 6 – 20 mm for bed joint thickness.
When the brick coursing is worked out in relation to the floor-to-floor dimension, the following dimensions should be added:
• thickness of shelf angle
• thickness of membrane and metal flashing on top of the shelf
• 13 mm first bed joint
• number of courses of brick times 200/3, less 10 mm from the total (assuming metric brick)
• minimum size of joint under shelf (to permit anticipated movements and changes of dimension determined in consultation with the designer of the building structure)
• 5 mm shelf angle tolerance
• 5 mm brick tolerance

The open joint under the shelf angle, required to avoid causing the brickwork to carry unintended loads imposed by the building structure, should appear in the drawings as the sum of the last 3 items. Reviewed by Guiseppe Strazzeri.

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