If you are building an octagonal or hexagonal shaped deck, the same steps apply; you just have more corners to true up. Always start with the straight lines, and incorporate the other corners one by one. Use the furthest diagonal points to check for true.
Once you have agreement all the way around, you move on to foundation placement.
Don't be intimidated by all of the steps above. This will only take you an hour, two at the very most if you hit a lot of snags. It really is a lot simpler than reading it looks like.
Next we move on to the actual building phase.
First, you will need to dig your foundation holes out. This is what the lines were all about, accurate placing of your foundations. This can be done in one of two ways. One way is with a manual auger, the other is one attached to a small backhoe. If you are in good shape, not afraid of hard work and do not have back problems, using the manual auger will save you some money.
I stress here that this is a very heavy, awkward piece of equipment that can do real damage to you, especially if you have rocky soil. When using the manual one, pull it completely out every six inches and allow the auger to empty itself. If you let it burrow down, you'll never get it out and you'll need that backhoe anyway. If you have a bad back, or aren't as strong as you once were, opt for the backhoe.
Now that you have your holes augured out, dump a couple shovels of gravel down in the hole and place your cement tube down there. Put another shovelful in, put your 4x4 posts in and shovel in your concrete.
I've found that the "Quickrete" brand works very well for this. Shove the post around a little as you fill it to get the concrete settled all the way down and remove air pockets.
You need to work fast now, fill in the rest of your holes and plumb your posts with a level. Make sure that you have them as plumb as you can because these are the main supports for your deck; everything on top of here is secondary. If you have more than four, fill two or three at a time and plumb those before you move on. Keep an eye on the posts for movement; check your plumb every so often.
Once your posthole is full, add a short shovelful around the top, smooth it down so that it is a little above ground, and sloped. Don't get it too thin near the top, or it will crumble. This helps to keep the mud and water from sitting in the top of the hole and rotting the 4x4 out prematurely. If at a later point you see the concrete crumbling around the top, use a commercial epoxy based concrete patch and re-seal the area
Once the concrete has firmed up, you can take a few days off while it hardens.
This is a good time to run through the rest of the project in your mind, so you know exactly what you will be doing.
When you go to pick out your lumber, make sure you get three nice looking joist boards, one will be your “face board” the one everyone will see usually, the other two will be the side boards, also visible just not as often. Use your best judgment for this placement. Make sure you buy longer lumber than you need. In other words if your deck is 8'x10' buy 10'x12', because the factory cuts are never dependable.
Now, remove the siding from where your ledger board will go. Use the same method you did for your stakes, mark center and measure out both ways. Use a chalk line to snap a line for you to follow, and use a square to mark your vertical line. Now use a utility knife and cut out your siding. Make a mark in the center of your doorway to line up the ledger board on when you install it.
Congratulations! You've reached the point of no return!
Next, cut the ledger board to size. Remember to subtract the thickness of your two outside joists, and then cut it to size. This board will go directly on the house.
If you were not told to use lag bolts when installing this, use lag bolts when installing this. This board is the main failure point of decks every year. Usually because people used screws, nails or staples alone to fasten it to the house, use 3/8” minimum, but no larger than ½” lag bolts, 3” long; also, use a decent sized washer along with the bolt to hold it.
