Question
QUESTION: Hi and thanks in advance for your help.

I have two questions, if you don't mind.

We want to put a flagstone patio behind the house and a large-ish (10 X 16 ft)single-story pergola spanning it. We're in southern Texas. The posts will likely be treated lumber cladded with 1x6.

1)What style of footing/anchor do you recommend for the posts? (our frostline is 6" deep, our soil is termed "expansive" and  termites are common.)

2) Is it best to set the footings and posts first then excavate and prepare for the flagstone patio or the other way around?

Thanks again!

ANSWER: Thanks for the question Mike. I am understanding that the flagstone is going to be dry-laid?

In answer to your first question,

You are in southern Texas, and I am wondering if you ever experience high winds or hurricanes?

If so, you may want to consider a "high wind anchor kit". This will provide added stability to the posts and anchor brackets. These bracket systems are partially countersunk as opposed to a bracket lagged to the top of the footing set at patio level.

Make sure you accurately set the top of the footings to match the thickness of the patio sub-base (Gravel), the bedding material (sand), and the stones themselves.  

To be even more detailed, don't forget to account for a slight slope for drainage. Use a laser level and some stakes to mark the final footing and anchor heights. Make the side you want water to drain off a couple of inches lower than the opposite side. (You don't want to have a couple of inches of concrete exposed after building your patio with proper drainage grade.)

Footings

For the cost of sono tubes and a few bags of concrete, I always have 3 ft concrete footings. (Or a minimum of 1 ft below the frost line.) With your frost line, 3 ft is more than enough.
More will never hurt you, but not enough can.

For your second question, I would excavate, prepare, and finish the pergola first. This is just much more practical. Working on the pergola after the patio is done involves risk to damaging or disturbing the stonework. It will also allow you to make any minor height adjustments if needed.

As far as the termites go, I have no experience with them. I do apologise. However, if you wish to ask me this question again, I can send it out to our answer pool for other experts to add their thoughts. Second opinions are always valuable.

Just a few thoughts for you Mike. Best of luck with your project.

Kevin

       

---------- FOLLOW-UP ----------

QUESTION: Kevin,

Thanks for the very complete and excellent answer.

I had one more little confusion to clear up, though. Regarding the sono tubes as you call them, do those get left in place or cut away once they've done their job?

Thanks again very much.

Mike

Answer
Hi again Mike.

This process of using sono tubes is covered on you-tube many times, so here are a couple of links for you. (It is so much easier to show you than tell you.)

As far as the excess, you can cut it off or leave it.  You should be setting the height accordingly so it won't be showing anyway for your application.

The first one must I believe is made by the manufacturer of the tubes. The second one is similar, and is made by quickcrete. Quickcrete products are pretty well known, and can be purchased at home depot and other large chains.

http://www.youtube.com/watch?v=hMwI97WQlOM

http://www.youtube.com/watch?NR=1&feature=endscreen&v=MCa_87Dkw1M

I hope this helps as well. Feel free to contact me anytime.

Have a great day Mike.