How to protect property form water damage

How to protect property from water damage

Managers can look for certain clues that can point to future water damage
Monday, March 3, 2014
By Sally Thompson

Almost all deterioration of building materials is directly caused — or exacerbated by — water. This is why in order to protect property from water damage, owners and mangers should observe what happens at both during a rainstorm and directly afterwards in order to correct issues before they become costly repair problems down the line.


Property owners or managers should check for areas of ponding, as this can indicate blocked drains or the need for additional drains or resloping. In particular, management should look for water near the building walls.

Landscapers tend to add more soil or mulch to gardens each year. Over time, this can significantly change the slope, often causing water to pool against building walls where it can lead to freeze-thaw damage to the cladding or leakage into the building.

On low rises, the discharge from downspouts should be noted. Is it running free and clear? Is the water being discharged where it will either cause erosion during the summer, or icing during the winter?

Exterior walls

The walls obviously will get wet during a rain, but what management wants to avoid is concentrated wetting, particularly with masonry walls. Saturated masonry will suffer more freeze-thaw damage, because the water in the masonry expands when it freezes.

If the walls appear dark and wet in a localized area after a rain, that means they are being affected by concentrated water runoff. To shed water better, management should invest in a sheet metal cap or some other type of flashing. A 25-millimetre drip edge installed early on can often prevent thousands of dollars of repointing and masonry replacement downstream. These flashings should ideally be installed when the wall is new, but later is still better than never.


Windowsills are intended to protect the cladding below, and most are designed to shed the water that sheets off the metal and glass components. For masonry, the sill protects against saturation-related freeze-thaw damage. For concrete walls, it largely protects against staining.

Managers and owners should first check if there are any ‘moustache stains’ under the windows. This indicates concentrated water runoff from the ends of the sills, which can be rectified by installing ‘end-dams’ in the sealant to push the water forward and off the sill edge.

Second, management should watch for over-caulked sills. When caulking, it is much easier for the contractor to completely fill the gap under the sill, sloping the caulking back to the wall. But this removes the benefit of the drip edge and puts the water back on to the cladding.

A properly caulked windowsill has the caulking recessed up under the sill so that the drip edge remains clear and effective. Correcting isolated over-caulked sills can be handled as maintenance, but a more widespread problem would need to be rectified at the time of general recaulking.

Lastly, management should particularly look at windows that do not have metal sills. Depending on the water runoff pattern below these windows, it might be wise to add sills.


Water often runs off the edge of a balcony slab and directly onto the wall cladding below. A well-placed bead of caulking or small metal drip flashing could help prevent damage to the cladding.

The other place for management to check is at the top of walls where they meet flat roofs. Here, parapets should have properly installed cap flashings that slope back onto the roof. If these are missing, the tops of the walls can become saturated, resulting in cladding deterioration.

Even if cap flashings are present, management will often see concentrated water runoff at the flashing joints. This generally indicates isolated over-caulking, as described for windowsills, and this can usually be corrected via modifications to the caulking.

Roofs and terraces

Visiting a roof during a rainstorm can be informative. There are often leaks into mechanical rooms, vents, doors and grilles that can go unnoticed for years, at least until they leak through into the suites below.

Some ponding on roofs during a rain is normal, because many drains have ‘weir controls’ that essentially trap water on the roof so it enters the city sewers more slowly than it would through uncontrolled drains. However, if ponding is still there 24 hours after it rains, this might indicate a blocked drain that should be cleared by a roofer.

And management should not forget terraces. These small roofs also have interior area drains that are often forgotten during annual maintenance.

Last but not least, property owners and managers should note any drains that pass through walls, often from balconies with solid guards or small upper roofs. These are often just small pipes inserted through the wall. If pipes have been installed too high, there will not be any water draining during a rain. If pipes have been cut too short, they may be leaking onto the cladding below. Extending these drains today may save management thousands of dollars in the future.

Sally Thompson, P.Eng. works for building engineering consulting firm Halsall Associates.

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