The Building Envelope Problems and Restoration
by Don Procter

Anyone who thinks the billion dollar leaky condominium problem is isolated to B.C.’s west coast, should take a closer look at condos built across Canada in the past decade or two where similar problems are cropping up. The key reason that problems are not as widespread may simply come down to distinctions in weather: the west coast gets a lot more rain then the prairies and central Canada.

Building failure investigators in Ontario says building envelope-related problems in relatively new buildings are on the increase and they look a lot like those on the west coast. “We might get less rain then on the west coast, but we still get it, so eventually we’ll see the same problems,” says David Dechamplain, senior project manager of the Ottawa branch of Morrison Hershfield Limited, an engineering company that does forensic investigations on leaky buildings.

While there are distinctions in building construction methods (traditional stucco is more prevalent on the west coast), what lies behind the claddings on both sides of the Rockies is similar. And that is where the problem lies, Dechamplain points out.

In Ontario, exterior insulated finishing systems (EIFS) are commonly applied to stacked townhouse-type projects largely because it is less expensive than traditional stucco and easier to install. But water infiltration is showing up in EIFS-clad buildings in Ontario along with brick, vinyl and even precast-clad structures because of improperly designed or installed building envelopes.

In the case of EIFS, Dechamplain says the majority of systems installed in the past decade or so are mechanically fastened or adhered directly to the back-up wall. The theory behind this design is simply to prevent any moisture infiltration. Nice theory. But practice has proved that moisture penetrates and then is trapped behind these “face-sealed” systems.

By 2002 in Ontario, the problem had been significant enough for the Ontario Association of Architects (OAA) to publish a rain penetration control guide that eliminated face seal applications over moisture-sensitive substrates such as gypsum. The objective of the wall design exclusion was to protect the Indemnity Plan from claims relating to exterior wall system failures.

“The industry has now realized that face seal systems are a problem,” says Dechamplain, noting that they have been commonly applied in three storey townhouse developments clad either entirely in EIFS or with a combination of brick and vinyl. The water typically gets behind the cladding at expansion joints, window perimeters, electrical fixtures, exhaust vents, patio doors or where two cladding systems such as brick and EIFS intersect.

Dechamplain says in many cases poorly installed weather barriers such as sheathing membranes are one of the roots of the problem. “There are a lot of cases of reverse lapping or instances where we find that the sheathing membrane doesn’t cover all of the substrate. Even in a cavity wall this can lead to moisture problems because the water gets behind the membrane, and into the wall cavity,

He says the problem is that the installation of the sheathing membrane and other weather barrier materials is often rushed prior to the installation of the cladding system and often left to unskilled labour.

Today’s EIFS manufacturers are now making drainage (rain screen) systems, rather than face seal ones, to ensure that any water which gets behind the cladding can return to the exterior. These systems might feature drain insulation board with grooves for moisture passage or notched troweled adhesives or adhesives applied with caulking guns in ribbon strips.

However, it takes more than a good rain screen system to ensure moisture isn’t trapped behind a building envelope. Returning the water to the exterior with through-wall flashing, used in masonry construction for centuries, is key to ensure buildings stay dry, says Dechamplain, adding that Morrison Hershfield’s forensic investigations of-ten find improperly installed flashing. In some instances metal flashing is fastened overtop (rather than underneath) the sheathing membrane, preventing water passage to the exterior. Another common source of water infiltration is where the bottom of the insulation board in EIFS is installed tightly against the metal base flashing.

“Installers have to be informed that the board has to be kept off the base flashing, even 10-millimetres is enough to let the water out.”

Other common sources of water problems are around electrical fixtures and mechanical ducts. Properly sealing the weather barrier around fixtures and ducts will prevent moisture infiltration. At windows and doors, subsill flashing is a reliable moisture-preventive measure. It involves wrapping the sheathing membrane into the rough-opening of the window or door than sealing it with caulking or low expansion insulating foam. “It creates a subsill drain. If the windows or doors leaks or the sealant fails, the water ends up in the sill by gravity but with the subflashing in place, the water will drain out,” he explains.

Dechamplain says moisture infiltration is cropping up in all types of new buildings. Highrise residential buildings that are typically clad in brick on an exterior gypsum board is an example. “We are seeing water getting behind the brick at all the same places plus at cracks in the brick or mortar.”

Building envelope failures often crop up sooner than many people might expect. Dechamplain has investigated buildings where indoor carpets are wet and hardwood floors buckling even before building occupancy.

But the worst cases are where the problem can’t be seen until years of moisture damage have occurred. The price for remediation is often high—$30-$50 a square foot. “In Ottawa, we’ve seen a lot of wood framed stacked townhomes 8-10 years old that need exterior wall replacement. I have a feeling that in the next 10 years we’re going to see a lot more of it because it is a type of construction that has been commonly built that is failing. Will it be as a big a problem as Vancouver? Probably not, but it will be a problem.”

He says while EIFS has had bad press, his investigations indicate that no one siding stands out worse than others. Blaming one segment of the industry is the wrong approach to resolving an industry-wide problem. “Design and construction have to be integrated so that all the details of the design are constructed properly. Often, there is not enough detail on water management in the building’s design, so it is up to the builder to figure out what to do on site.”

Making matters worse, in the business of construction where many subcontractors scurry to fast-track deadlines, it is difficult to schedule each subtrade sequentially. “If there is not enough coordination on a construction site and a window or siding contractor arrives and the weather barrier isn’t completed, they may go ahead with their installation even though the weather barrier should be in place first.”

The problem is compounded by the fact that even municipal building departments don’t assess a design’s weather barrier and flashings.

Dechamplain says the entire building and design has to make adjustments to curb the water woes. Designers must provide detailed appropriate designs and make sure that those designs are followed by the contractors. Quality assurance programs would ensure the objective is met. “Contractors have to be educated to understand what the design intent is on a project- by-project basis. Is, for example, the Tyvek acting as an air barrier or is it just a weather barrier? Or is the Blue Skin just a flashing or is it an air barrier, flashing and a vapour barrier? These new materials can play so many different roles, so if the contractor doesn’t understand what the designer’s intent is he might not do what is required to keep moisture out.”

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