Exterior Wood Stair Problems

Wood and cement are not a good match. The wood needs to be separated from the stucco or concrete some how or you will have to expect some sort of damage to the building latter on. The stairs in the picture above look like they where built after the building stucco was done.

One of the problems here is the white arrows pointing to a water/wood problem. When it rains the water that hits the wall will roll down in between the stairs and the wall going under the stairs with no place to drain off to. The water will sit in this unexposed area creating mold and mildew creating a musty smell.

wood stairway next to stucco building and water leaks

Here's the complete stairway and even though I don't have a picture of it, there's actually a door on the opposite side that leads to a storage area underneath the stairs. I can only imagine how much water damage, mold and mildew are under this area, especially if it doesn't have some type of waterproofing system protecting it. small gap can allow water inbetween wood stairs and stucco wall

Here's a section or cutaway of the stairs if you were looking at it from the front of an individual step. In this illustration you can see how the water works its way in between the stuccoed wall and wood stairs.

It won't take much of a gap for water to work its way through and it won't be a problem as long as it doesn't get trapped and can dry out within a short period of time, but can be a problem if it works its way into any area that won't allow it to evaporate quickly.

A closet or storage area under a set of stairs is the perfect example of something that will trap moisture for a long period of time.

flashing can prevent water passing inbetween wood stairs and wall

Here is the same view except for that metal flashing has been installed before the stucco, but after the stairway has been built. A stairway like this would require metal flashing along the edge of the wood stairway, where it meets the main building wall.

Obviously this would be difficult to do after the building had been built and exterior walls had been stuccoed. These are things we need to catch during the design phase and if not, then a different type of stairway should have been installed, during the remodel.

how water get deflected and not trapped inbetween wall and stairway

This illustration provide you with an excellent example of how the water would safely drain away from the building, even though it wouldn't solve all of our problems, because even if the water was draining away from the building, it would still get trapped in between the stair treads and risers that have not been properly waterproofed.

I think the only way you could fix a situation like this, if it was a problem, would be to remove the closet or storage area under the stairs or remove and rebuild a different type stairway that could be waterproofed correctly.