Robert Lamoureux | Waterproofing: How to make the pergola perfecto 

Robert Lamoureux
Robert Lamoureux

Question: Hello Robert, thank you for what you do here in Santa Clarita, answering all of the questions to help those of us who don’t know where to turn for sound advice. I’ve learned a lot through your articles, and have saved money by having the confidence to do some work myself on our home. I haven’t written in before, but this time I know I need proper information before proceeding.  

I know you’ve covered this before but I cannot find the article and I need to do this properly for the sake of safety and making sure the end result is water-tight. We are planning to put a pergola/patio cover into our backyard patio, and want to attach it to the house, due to the configuration of the yard and it being on the south side of the house. A separation from the house, we’ve considered, but that gap would allow sunlight and heat to penetrate the main room, which is what we are trying to prevent.  

The exterior of the house is stucco and I know we need to break that out and tie into the framing of the house. I am confident in the framing/building portion of the project, but I am not familiar with the process of waterproofing once we are done with the framing.  

With that said, I have two main questions: One, do I need a permit for this work, as I am doing it myself? Two, can you explain the general process of waterproofing this properly, so that I don’t have to worry about a failure with future rains?  

The rest of the project I am OK with, but want to close this up tight so that I just don’t have to worry about any water intrusion later. Thank you for any help you can offer on this.  

— Joe J. 

Answer: Joe, you are far ahead of the game. If you are savvy with the framing and can build this yourself, you will save a ton of money. Question No. 1, yes, absolutely you need to pull a permit for this work. It’s relatively simple: Create a drawing of the design and list the details of the lumber and dimensions you are intending to use, and take this to the Building and Safety department. They will review the engineering/design and either approve as is or determine anything needed to be changed in your design.  

Once they approve, you’ll receive your permit number and you may begin the building process. Be sure to get necessary inspections prior to moving on to the next step, so you have approval and confirmation that your work is sound. Once the project is complete, always be sure to get final approval signed off, and save those documents through the life of your time owning this home. At the time of any potential sale, you will need to confirm if this project was legally built to code.  

On to question No. 2, waterproofing. This is an outstanding question and one that will save you potentially tens of thousands of dollars in damages, when done properly. I have personally repaired hundreds of improperly waterproofed projects over the years, situations that could have been avoided if only done correctly in the first place.  

Stucco will need to be cut out at least 12 inches above the area being tied in to, which is the ledger board of the second floor to the home. The biggest thing to check for once the area is opened up is that the existing waterproofing paper is in good condition. Note that if it is not, this could be a can of worms that you’ve opened, as no new paper can be added to failed paper, because it simply will not work.  

If by chance you find failed paper, you must continue to open the stucco until you find good paper to tie into. Side note: Wait until the rains are over for this project. Do not open this to the elements until you know you have enough good weather to finish this project to its completion.  

Installing new paper is relatively simple. Make sure that the new paper goes UNDER the old paper, so that water runs down to the bottom and not into the next layer.  

The final thing, to ensure that the water runs away from the house, is installing a “Z bar” flashing, which undermounts the bottom of the paper at the ledger board. 

Just like the paper, the flashing will tie in under the bottom of the paper, so that the water eventually falls onto this flashing and is directed away from the house and onto the top of your new patio cover. 

The last step in this portion would be a waterproofing system added, to keep water away from the lower patio area. Given that the patio cover is sloped properly away from the house (this will be part of the design/permit process), water will drain away from the house. Once all of this work is done, if you are not versed in stucco, I’d hire a licensed and insured stucco contractor to close this up and match your existing stucco as closely as possible. This is where I’d hire out, so that the finished look is as close as possible. 

Stucco is a bit of an art form and a first-timer will likely not get a professional look. This is just my experience. If you have any questions along the way, reach out and I’ll help. Best of luck. 

Robert Lamoureux has more than 40 years of experience as a general contractor, with separate licenses in electrical and plumbing contracting. He owns IMS Construction Inc. in Valencia. His opinions are his own, not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor after that contractor has made a thorough visual inspection. Email questions to Robert at [email protected].      

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