Brick parapet: What's causing this secondary leakage

The upper line of leakage represents the roof elevation and is caused by long term moisture seepage through the brick parapet wall caused by inadequate roof drainage. What’s causing this lower band of deterioration?

1 Like

Is this one of your quizzes? well, I will take a shot at it and say, condensation caused by a lack of insulation at the ceiling line. Just throwing it out there Kenton.

Been racking my brain on this one Kenton. My first answer would be the lower band of deterioration is being caused by the upper… :stuck_out_tongue:. But from the naked eye, if the upper was caused by poor drainage, lack of flashing etc. I would presume the lower was a result of the same with water being redirected between the roofing rafters down to the ceiling rafters. I don’t know but thanks for the “puzzle”… :wink:

I posted that i another forum and that agrees with the two answers I’ve gotten Scott, except that they both stated it as inadequate venting of the attic, which is similar. I’m guessing that the undamaged space between the damaged areas represents the roof structure and the top of the lower damage is the bottom of the roof framing.

1 Like

Obviously, there is water intrusion in the brickwork from the coping or the flashing on the backside of the parapet wall. A view of the backside of the wall would help. It would not surprise me that moisture intrusion from those capstones are part of the problem along with flashing and moisture intrusion at the wall intersection of the roof framing bearing points.
Here are some good details for parapets along with moisture intrusion points.
https://www.mtidry.com/blog/moisture-management-of-parapet-walls/

I had the same thought Marcel, but don’t understand why moisture intrusion from above would accumulate at this lower level. The airspace would have to be interrupted at that level.

After looking at Marcel’s details, condensation could be a factor,

I’m in the process of expanding the Reference section of my website and at the same time, adding links to the various pages to my Spectora template. This allows (especially newer) inspectors to have onboard reference material they can refer to during an inspection if they see something they don’t understand. I have several pages about different kinds of brick failure, but here’s the one I’m working on for this particular condition.

For interior I have
Kitchen Checklist

Stair Checklist

Hardwood Floor Checklist and Diagnostics

Door Checklist

Window Checklist

Thermal Pane Window Failure

and so on…

Some software allows live links and some doesn’t. In HG I have put a lot of this reference into the CYA already, but CYA doesn’t allow photos, so the links to my web pages are an advantage in that respect.

2 Likes

Kenton, I fail to see why inadequate drainage has to do with moisture damage to the brick facad’.
If the backup block or brick to the veneer or multi-wythe brick wall is properly flashed to the roof, water infiltration would not be coming from the inadequate drainage.
To cause that brick damage, moisture is entering the wall via the cap, the brick facade, or the flashing. Any moisture or condensation should be going down the cavity and out the weep holes. If not, you will see trapped moisture cause problems like the picture you posted.
The inspector is not there to figure out the cause, so with this obvious problem, a Mason Contractor would be advisable for further evaluation of the problem.

image
Did you mean to write “not the failure”?

Marcel, I know wall cap leakage is a common source of intrusion of the parapet walls, but what stops the downward movement of moisture inside the wall and makes it migrate to the outside right at the roof line (unless the parapet is not a continuation of the exterior walls).
I had assumed it was inadequate roof drainage along with flashing failure at the wall/roof junction that allowed seepage through the wall at the roofline.

Why I mentioned a view of the backside would help in my first post.
In these older buildings, it was common to fill the cavity full of mortar when doing the masonry around the wood framing or metal joist at the bearing location and just continue on up to create the parapet. So by doing so, any moisture intrusion or condensation within the cavity would be trapped.
I can’t explain the bottom one without knowing the construction of the wall, and roof construction which I can’t do, obviously.

…and this is just a photo I took from the street, Marcel. I see what you’re saying, if the parapet cavity was blocked at the roofline, and especially if the flashing were intact, cap leakage would be a more likely source. Being able to look at the interior of the parapet and at the cap would help and the age of the building would count too.
Also, in looking at the photo, discoloration is visible in bricks in the face of that middle raised section, which also indicates cap leakage. I just rewrote that section.

Inspecting a building and pointing out what is wrong is the easy part. To diagnose from a photo is impossible. Further investigation is needed like finding out if the coping is leaking, checking to see if the backside of the parapet is properly sealed. What is the construction of the parapet, is it a brick veneer or a multi-wythe brick wall, or does it have a brick with a block back-up. Does it have proper wall flashing at windows with weep holes. Is the roof framing inside the wall with masonry around it. Was it steel joist bearing on masonry. Did it have an EPDM roof with a termination bar on the backside of the parapet. Is the roof covering a type that may be contributing to the problem?
A proper forensic investigation is required to find out the real cause of the problem. Anything else, is just speculation.

2 Likes

Not only the band of masonry at the lower parapet is laden with moisture. Below the window sills as well.
Commercial building.
Prior repairs. Poor workmanship.
1: Lack weep holes to disperse condensate and circulate air in the mid-wall.
2: Building bloom.

Cause. No air circulation in the mid-wall assembly. Mortar buildup in the mid-wall assembly at critical intersections requiring weep holes causing the brick masonry and mortar to wick bulk water…

Just my 2 cents.

Some low slope roofs on older buildings were built like a floor truss with an upper chord and lower chord that varied in height from front to back. There may be a ledge the bottom chord sits on.

1 Like

Inadequate insulation in the rafter box sills?

Meaning that the parapet is a structure separate from the outside wall and the space between top and bottom chords might allow condensation to accumulate enough to cause the lower damage?

Looks like it’s corbeled at the upper brick, look at the corner
Capture

1 Like

Good eye Rodney! Also looks like the lower level is slightly offset also. No mortar lines visible at the viewing angle.

brick