(12-06-2025, 05:04 PM)eizenstriet Wrote: May I ask ZEBuilder, what are the relative costs and the upsides/downsides of precast v. poured-on-site concrete?
It often times comes down to site specifics when it comes to making the decision of precast vs cast-in-place (CIP).
In general precast has greater control when it comes to the concrete curing process which can lead to better overall quality compared to CIP. CIP has the downside of dealing with the weather which can greatly affect the quality of the poured concrete. Concrete is a temperature dependent material, temperature control is often required to make sure it cures appropriately onsite, this can be controlled in two manners, the first through the use of admixtures (chemicals put into the concrete), the second being on site control (tarps, heaters) which is just more cost that you have with CIP that you don't have with precast.
Similarly precast generally requires less labour when compared to CIP, with CIP you have to set up and take down forms which adds significant labour cost in compared to precast, pour concrete (cement trucks, pumps) where this is very automated in a factory setting, with very few on site trades, for example a typical Stubbe's precast crew is 5-10 people, CIP ranges significantly based on the contractor so there isn't a firm answer but generally the projects that move faster have more staff.
Another thing to consider is speed, in some cases precast can be faster than CIP but in other cases CIP can be slower. It generally depends on the contractors involved. For example it's not uncommon for CIP to do a floor in 4-5 days when you're in the tower section of a building, forms are repetitive, this was the case for Station Park and numerous other projects in Ontario. That speed rivals precast which is where the other points mentioned come into play.
In most developments that use precast you will see the underground levels and podiums (especially when there is parking) utilizing CIP, it's not impossible to do with precast but those sections of buildings are typically more intricate which means some of the benefits of precast are lost. Podiums and underground levels generally have less repetition (where precast thrives), and more complicated structural layouts (transfer slabs and/or beams).
In general precast tends to max out in height around 25-30 floors. It is possible to use precast higher but it generally requires greater amounts of CIP to deal with the larger wind loads and seismic design loads, there are constantly advances in precast that have allowed for greater flexibility in design, hence this may not be true 10 years for now. This is why you see most buildings 30+ floors using CIP (Charlie West, Station Park T3, Duke Tower, TEK Tower) whereas buildings that are shorter have used both CIP and precast or total precast (900 King St W, 100 Vic T2, 1001 King (Eureka)).
Overall it just comes down to site specifics and developer preference which takes into account everything mentioned above.
