Robert Lamoureux | Is Dutchman repair a viable option?

Robert Lamoureux
Robert Lamoureux
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Question No. 1 


I have a large beam on our pergola that is partially rotted that I’d like to repair. I remember vividly, you wrote about a Dutchman repair to a similarly rotted timber. In my situation, can I do the Dutchman repair? 

— Richard W. 

Answer No. 1 


It is difficult to be accurate not being on site but the rule is that if more than 25% of the horizontal member is damaged or rotted and the load is downward, it looks like it is not a candidate for the Dutchman repair. If that is the case, you’ll have to break out the stucco, disassemble the entire pergola and replace the beam. 

A large beam on a reader’s pergola is partially rotted. Contracting expert Robert Lamoureux says if more than 25% of the beam is damaged or rotting, it is not a candidate for the Dutchman repair. Courtesy photo

If this beam is carrying the brunt of the load of the pergola be sure you are assessing this beam properly before deciding. 

Remember, 25% is the rule. If you are close to that, I would err on the side of caution and move forward with the replacement vs. a repair. If you are below the 25% mark, then you are free to cut out the damage and replace it with a tight-fitting block. Screw and glue this block into place, followed by filling any gaps, and then finish with prime and paint. 

Following, stay on top of the maintenance of the rest of this pergola, meaning that when the paint is wearing, immediately get to sanding and sealing once again. 

Wooden structures outdoors are beautiful but they are not without the need for maintenance every few years, depending on weather and placement. 

Generally, a south-facing structure will take more abuse from the sun, so any finish will wear faster. Best of luck.

— Robert

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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