Picture of How to Build an Octagonal Deck
This is a 12 foot Deck I built in 2005. It has gone through 6 Canadian winters and one restain of the deck surface. This instructable will cover each step with pictures and the Bill of Materials. The costs shown are from 2005, with the total about $1500 Canadian, not counting tax, the cost of the tent, or maintenance. 
Remove these adsRemove these ads by Signing Up

Step 1: Materials Required

Picture of Materials Required
Tools required are:
Hammer, 4 ft Level
Clam shell shovel or post hole auger
Powered hand drill (I used a 1/2" hammer drill.)
Hand Circular saw (mine is a 7-1/4".
Showel and Wheelbarrow
String and chalk

Your skill set is that of a man or woman handy Person
(ie fearless and willing to make mistakes, Measure twice-cut once person)

Step 2: Chalk Out the Deck

Picture of Chalk Out the Deck
This is a 12 ft diameter cantelevered deck, with poured concrete piers. what follows assumes you will want to attach the deck to the house.  Find a spot 6 feet from the edge of your house (plus an allowance for a ledger board) more or less centred on the house entrance. Mark this spot as the central support column of the deck. Drive a peg. Attach your string to this peg and, draw a chalk circle of radius 6 feet and a second circle of 4 feet. Start marking the position of each of the 8 support post. String a line to the right edge of your door and driving a peg at the intersection of this line and the 4 foot circle. Carefully counterclockwise rotate the string 45 degrees. Strike this second chalk line and hope the subtended angle covers the door entrance. If it does, drive a peg at the 4 foot intersect. If it doesn't, fiddle with these two lines so that the45 degree arc is centred on the door frame. After these first 2 pegs are in, progess around the circle until all post holes are pegged. 
67spyder3 years ago
I never use a ledger board when I build decks or steps, this will trap moisture between the ledger board and the house. With a wood construction house this causes rot and with a masonry house like yours the trapped moisture is hard on the brickwork during freeze/thaw cycles. The deck you have built would be stable as a free standing structure with a small 1 - 2 inch gap between it and the house to prevent trapped moisture. People don't even notice the gap and it prevents some painful repairs 10 - 15 years down the road.
cobourgdave (author)  67spyder3 years ago
Thanks for your warning. I will in fact check for damage this summer.
Since the brick is very roughly textured, I am HOPING that sufficient air flow has taken place to prevent spalling on the brick. There is certainly not a 1" gap, more like 1/4".
If damage has occured, or even shows a possibility, I can pull the ledger board
and take your suggestion. The deck is very sturdy as a free standing structure, and since all parts are screwed together, I can disassemble the areas adjacent to the ledger board very readily for any changes required. It was built in 2005, so any incipient damage will be fairly obvious.
Thanks again for your thoughtful feedback.
The mortar between the bricks is most likely to suffer.

I recently discovered an unexpected benefit to building decks as free standing structures. Someone was backing a truck up to a deck that I built several years ago and accidentally hit the deck. Instead of doing a bunch of damage to the house the deck just moved off the concrete weirs that it was on. I was called to fix it and all we did was come with a bunch of guys and just put it back!

Most "professionals" will say I am wrong, that you should use flashing and caulking to keep the ledger board dry but omitting it is easier and more effective as caulking and flashing always fail on level surfaces like decks.
you should check with local building codes.. where i live it is required by the county to have all decks or other such structures attached to the house WITH a ledger board and they have regulations as to the size of fastening screws attaching the ledger board as well...

Beautiful pogoda btw... thank you for sharing.
dfc849 67spyder3 years ago
Your input definitely would have helped me about 7 years ago.. we noticed damage caused by moisture last year because of this. 10-15 years like you suggested may be average, but depending on the size and circumstances of the build, we can see negative effects as early as 6 years in my case.

Otherwise WONDERFUL instructable, with detailed instructions and photos.
cobourgdave (author)  dfc8493 years ago
Appreciate the comment, thank you. As 67spyder has noted, trapped moisture is a problem. Your comment of similar damage underlines that we can't just build and leave, we have to spend some time in checking for things like water damage, trapped moisture and so on. Thanks to 67spyders comments I will be spending time checking for this and other types of damage when I sand and restain the deck surface this coming summer.
skoutelas3 years ago
nanosec123 years ago
What a beautiful addition. I had to build a deck for my wife, but fortunately for me there was no complex math (mine is rectangular)

Great Job
cobourgdave (author)  nanosec123 years ago
Thank you for the comment. I am surprised by the number, but definitely appreciate the numbers of positive comments on my first instructable. You guys have really been supportive.
Very, very nice. I might have considered doing something like this on my side if I didn't already have the cement deck to begin with.
cobourgdave (author)  David Catriel3 years ago
Thanks for you comment. Maybe your next house?
Could be. But after the work I did on the deck (see my instructable; I'm sure you can sympathize), I don't think I'm yet ready for another big project like that.
cobourgdave (author)  David Catriel3 years ago
Actually, I had looked at your project before, when I was browsing a large number of instructables to get an idea what was the type of project Instructables was looking for. When you mentioned it now, I went back for a second look. Indeed, you spent as much time, or more on your project than I did on mine. As you indicate, a lot of work. I have to congratulate you on your's, and would agree it is not yet time for another bigee.
Glad you enjoyed it. But you never know; the wife might get me to add a third floor or something one day. Stay tuned ...
jtreadgold3 years ago
This does not meet code in Canada. The deck needs to be at least 100mm below floor height inside the door. This alows for snow melt outside not getting into the house as the door sill is usualy above the floor height bi at least 25mm.
cobourgdave (author)  jtreadgold3 years ago
Thank you for your coment. In fact in the town I live in, which is in Ontario, I took the precaution to review the plans with the town engineering department. No mention was made of deck height below door entrance. Undoubtedly, other jurisdictions have different requirements. The building codes for Canada as a whole will reflect the a more conservative approach to snow load, but local jurisdictions have priority over federal codes, and will differ widely dependent on location. The town I live in borders Lake Ontario and the snow fall has been moderate for many years, so I presume building codes are applied with that in mind.
Should I be living in a heavy snow area, the design would have reflected the realities of the environment. I am sorry if I gave the impression that my design would apply to any and all jurisdictions; in fact I didn't think the instructable had to do so. Why not redesign my approach to show how it should have been built in your jurisdiction?
sfrazier3 years ago
Sorry about the gazebo dimension, but it worked out beautifully. The extensions really enhance the overall appearance. But as the whole thing goes it's an incredibly beautiful deck. Let me know when you have some free time to build in my yard. :D
cobourgdave (author)  sfrazier3 years ago
Many thanks for your kind comments. Indeed this was a "oh darn" moment with my wife and myself. The tent was great, except... ! Regardless we agreed it was a beautiful tent at a good price, and decided to adjust for it.
sumomo3 years ago
cobourgdave (author)  sumomo3 years ago
Sorry, I can't understand your comment, but based on the step you were at when you sent your comment, I would guess you were concerned with the use of the saddles. I will try to explain. The saddles are used to assure that the upright 4"x4" posts will be aligned so that the rectangle boards of the foundation will meet at right angles with the posts. Since there are two interlocking rectangles, the ODD post are set aligned just 45 degrees rotated form the EVEN posts. I hope this helps, and thanks for your comment.
foobear3 years ago
It's fantastic. Did you have to get a permit?
cobourgdave (author)  foobear3 years ago
Fortunately no. In the town I live in, if the deck is no higher than 24 inches, you don't require a building permit. As it happens, my deck on average is just 24" high. Zoning bylaws also proved set back rules. Here a deck with no roof or at least not a hard roof have a 4 foot setback, adding a hard roof changes the setback to 23 feet. Thus I was able to add the tent to the deck. Regardless, I still had to apply at the engineering department of the town.
Thanks for your question
Topcat20213 years ago
Great Job, It is a beautiful addition to your house keep up the good work.
cobourgdave (author)  Topcat20213 years ago
Thank you. It was fun building it.
Schuyler3 years ago
Beautifully done. However, if your posts are all laid out perfectly to begin with, I see no point structurally(at all) for the sub-frame.
cobourgdave (author)  Schuyler3 years ago
Excellent point. You could indeed skip the foundation with a perfect layout of the posts. I included this substructure because it provides a way of laying the deck without concern for post shift due to freezing and thawing as well as ground shift. And yes, I admit, I don't think I ever layed out anything perfectly and the foundation structure allows for a lot of "oops" moments. Thanks for your comment.