Q&A / 

Brick Leaks

DEAR TIM: Every time a wind blown rain saturates our brick veneer home water streams into our home. I have noticed that the wood floors in our living room are warping as well. The brick and mortar appear fine. What is causing the leaks? How should the brick have been installed? What, if anything, can be done to stop the water penetration? Brenda F., Brockton, MA

DEAR BRENDA: I hate to tell you this, but you have some very serious problems. If they are not corrected, serious structural failure will possibly be in your future. I'm quite confident that if I did a post mortem examination of your brick walls, I would find serious workmanship errors.

Virtually every brick wall will allow water to penetrate. The water has three possible paths. It can enter directly through the brick, the mortar, and/or the contact zone between the brick and mortar. The primary path of water into brick walls is the contact zone between brick and mortar and mortar joints that are not filled completely. Your wall leaks, I will wager, are most likely originating at the vertical joints between many of the brick. Bricklayers call these head joints.

Can you see what I see?  No water membrane covering the wood framing! What's more, do you see any weep holes? I sure don't.


The quality, type, and moisture content of the mortar is a critical factor in preventing brick veneer wall leaks. The mortar for a brick veneer house needs to have a high lime and low cement content. The lime in the mortar, through the years, can actually heal tiny cracks that might develop between the brick and mortar. Mortar that is too wet or has too much cement can shrink as it dries. This shrinkage can produce tiny cracks that allow water to easily penetrate the wall.

Older brick houses usually were never a brick veneer. Often the brick walls were two, three and sometimes four brick thick bonded with lower strength, high lime content mortar. The inner courses of brick were very soft and absorbent. Rain water would collect within the wall and then be released to the atmosphere once the storm passed.

Modern single thickness brick veneer walls deliver the wind driven rain within a matter of minutes to the wood frame system just on the other side of the brick. This water needs to be collected and transported immediately to the exterior of the house. This is accomplished by installing high flashing materials at the base of the brick wall, above all doors and windows, and below all window and door sills. The flashing must be continuous and needs to be made from a material that allows joints to be permanently sealed. High quality brick veneer flashings can be made from modified asphalt and high quality polyethylene and copper / asphalt combinations. Do not use the low quality "garbage bag"or PVC type plastic. It is useless.

The exterior of your wood framed walls should also have been covered with a water resistant membrane. Overlapping horizontal pieces of time tested tar paper will work. However, there are many air and moisture barriers that will do as good a job or better at preventing the leaking water from contacting your wood framing. These moisture barriers must be installed so they lap over the wall flashings. Weep holes at the bottom of all walls and at the top of windows and doors need to be no lees than 4 feet on center. 2 feet on center is preferable. The cavity behind the lowest courses of brick needs to be free and clear of mortar droppings. This allows leaking water to easily escape through the weep holes. An ingenious saw-toothed plastic netting can accomplish this task easily. It fits behind the first few course of brick.

Your leaks may be able to be stopped with the application of high quality water repellents. These materials contain special chemicals called silanes, siloxanes, or a blend of the two. First you must closely examine your brick walls. Look for tiny hairline cracks in the vertical joints. Remove and install new mortar if you find obvious water entry points. After the joints dry, apply the water repellents according to the manufacturer's instructions. A second application may be necessary. If this does not solve your leak problem, I'm afraid that your only solution might be to re-install the brickwork properly.


11 Responses to Brick Leaks

  1. I would like to know the names of brick repellents for crumbling red brick
    If I use the repellents on the outside wall; how do I apply to already paints walls on the inside walls. Trying to drill out holes on the inside building to attach false wall but find the bricks are crumbling when trying to drill through.
    Any suggestion . Thanks Rita

  2. Tim,

    I have leaks coming into my brick in my attic. There is too much mortar on the back of the brick and very little tar paper. The water is going through the brick over the large deposits of mortar and into my house. I have a guy who wants to apply some kind of fiberglass mortar (or something ) to the inside (which is my attic) and then put up tyvec or tar paper. He advised that after this he would repoint the walls on the outside. What are your thoughts?


  3. I have a garage with brick veneer that leaks into the garage from under the sill plate. The brick is below grade level which I think is the problem. Regrading really isnt an option. Is there a way to pull the dirt away where the brick meets the footing, place a waterproofing material at the seam then back fill? If so can you recommend a waterproofing material?

  4. Brick leaking can be resolved by wrap the house? Which material is the best choice ,of course ,not very expensive.

  5. I have a 1980s detached brick built house. In 2011 I had cavity wall insulation installed,since the New Year when we have experience
    wind driven rain the south facing wall has allowed water to leak into the conservatory over the back door and window lintel in several places through the brickwork. The same appears to be happening over the exposed windows. Any advice would be appreciated.

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