Expert: Bruce E. Johnson - 7/6/2009

Question
I am planning to put a pergola on a patio that I haven't laid yet.  Should I lay the gravel base and plate compact it then dig the holes for my 12" round concrete tube footings, or can I dig the holes now, then lay the gravel and plate compact around them.  Also, what's the best way to secure the 6"X6" posts, bury in concrete or on top with some sort of bracket?  Lastly, how deep do I really need to be?  The pergola will be 16'x16' and I live in Eastern Washington state.  Thank you!

Answer
Hi David, you can do it either way.  If you dig the holes first then you should probably fill them with concrete before finishing the slab preparation.  If you plan on pouring the pads and the slab together then you should dig the holes after to keep them from caving in during the compaction process.  Simpson makes some great post anchors for this type of work..Go to Simpsonstrongtie.com..you can download the Simpson catalog and find the post base that fits your needs.  I prefer the type that embeds in concrete with heavy guage galvanized vertical steel straps for a freestanding pergola unless you plan on using some sort of knee bracing to keep the sway out of the structure.I don't recommend embedding the post into the concrete, it will rot out eventually. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com