Foundation Elements vs. Foundation Systems
By Jon Eakes
Pouring pillars has become simpler with Maritime products such as Big Foot and The Footing Tube that allow a single pour for footing and column.
Then British Columbia got into the innovation competition with a cloth-type tube that comes all rolled up and, after the column is poured, is stripped off. Any height you want is available in a single roll called Fast Tube.
All of that just to say that innovation never stops and even something as apparently simple as a concrete pillar needs to be thought through before starting. You need to study what it is to accomplish, what environmental conditions it will have to deal with and how to get everything done cost effectively.
Insulation, drainage layers and other moisture controls are things that we talk about a lot, and we struggle to understand the relative merits of different products.
Air gap membranes, dimpled sheets of plastic that serve first as wall moisture barriers with a back-up of clear space drainage have a solid position in the trouble free basement competition, the best known being Platon and Delta-MS.
In addition, Delta-Drain is a new product designed for handling regular and heavy water flows, such as on a hillside, that reverses the strategy and gives drainage as the first line of defence backed up by a moisture barrier.
Dow's Perimate has vertical grooves in the backside of a rigid foam panel to provide a water drainage path. Interestingly, Institute for Research in Construction (IRC) research ended up demonstrating that the grooves in foam boards were not necessary and neither was additional damp proofing - any rigid board insulation does a fine job of insulating, damp proofing and the rough interface between the wall and the rigid foam board appears to provide a very functional drainage path, without grooves.
Glass fibre and rock wool insulating/drainage boards came into the competition and independent research at IRC has shown that water drains quickly and efficiently to the bottom without affecting the insulating capacity of the boards. Fiberglas BaseClad was taken off the market when Owens Corning brought in their line of pink extruded polystyrene, but Roxul's DrainBoard is still available.
Because all of this is so confusing, the IRC went to work on a major project of understanding basements -from why we make them, to what we expect from them, to how to accomplish that and at what price.
If you want to seriously understand basements you should read the free 200-page final report from the IRC: Performance Guidelines for Basement Envelope Systems and Materials, October 2005, which is available as pdf file on the Web. This is a surprisingly well written and understandable primer on what really goes on under the house.
Most of the study was completed in 1999, so it is interesting to also read the 2006 update of the cost effective analysis of different basement systems in different regions, CMHC's Economic Assessment of Basement System Insulation Options: Final Report (go to www.cmhc.ca/en/inpr, and then Order Desk, Research Highlights, Technical Series, 2007, and document #65346).
A few striking notes from these reports: The building code does not define the end use of a basement and, as such, the minimum requirements of the code will create a strong foundation but cannot assure a comfortable and healthy living space under all conditions. This study found it necessary to establish a whole series of basement "types", from structural foundation only (Type E) to storage (Type C) to full living space (Type A-1) as a first step in determining what system components were required to accomplish the consumer objective for this space called a basement and concluded that most basements must be built beyond code to make them a living space. The study gives very detailed information on how to pick the right system components for specific objectives under specific conditions.
Individual site and climate conditions, even in the same development project, can require changes in system components to achieve the necessary performance of a basement for the use type targeted.
Initial drying of wet walls (both poured concrete and mortar with blocks) is a significant first-year problem that requires special attention when using several common basement systems. Thermal bridging was a more important heat loss factor than was expected, potentially dropping the insulation value of a wall by as much as 30 per cent.
Insulation cannot be considered separately from the entire basement system and this is both in terms of performance and cost effectiveness. The common view that exterior insulation systems are significantly more expensive than interior systems was not confirmed in the study when building an A3 (Near-liveable) basement or better, and this was generally true right across the country.
From a customer satisfaction and cost efficient (profit) point of view, if you read only one research report this year, this should be the one.
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