Securing a Pergola to a Deck

On the topic of where to build a pergola, this question very frequently comes up:

“How do you build a pergola on a deck that will stay secure under windy conditions? We live in a hurricane zone and we’ve seen pergolas that crumble and other’s that stand strong. What’s the key to keeping them secure?”

It is very important to properly attach pergola posts when installing a pergola over a deck. As the customer shows, a main concern is how the structure will react under high wind conditions.  Most deck builders bolt pergola support posts to the frame of the deck using (2) 1/2"x6" lag screws with washers per post. The key there is to attach the posts to the frame. That is the only part of the deck that can provide the stability to hold up any kind of attachment to the deck. This technique is the same as attaching a rail post.  

Another way to insure stability is to build the pergola with some additional bracing pieces that increase resistance to wind. Pergolas are top heavy and can sway in the wind without lateral bracing and can experience strong uplift forces as the pergola acts as a sail.  Attaching sections of rail in between pergola posts will strengthen the pergola.  Installing 45 degree bracing in between the post and header beam will also increase stability. 

For just about any design or foundation, we always suggest using 6x6's for support posts, but for a deck we consider it mandatory.  Deck Lok brackets are another option for extremely windy areas and hurricane zones.

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