Step Two of Building a Deck

After mounting your ledger board the next step is to lay out the deck and the foundation that will help support it. The foundation consist of a pier resting on a footing. Your best friend in this step of building a deck will be your mason's line. Using a mason's line will guarantee that you post will be square and the start of the deck building process will be accurate. Remember, this is the step that sets up all the other steps in building a deck so you need to get this one right. Hurrying through this step and saying "oh, that's good enough" will not due and you will suffer greatly in later steps.

First you need to map out the spacing of the posts on the ledger, then drive in nails to mark the center points. Tie a mason's line to each nail, run it a foot or so past the outside edge of the deck and tie it to a batterboard. A batterboard is basically a home made structure for you to use in place of the actual beam and by using this system you can assure perfect placement. Level the lines with a line level, driving the batterboard farther into the ground as necessary. To build your batterboard simply build yourself a 3/4 square using 1x material. To check that each corner is square, apply the 3-4-5 triangle principle. This is a neat trick and it works every time. Make a mark 3 feet along one side and 4 feet along the other side. When the diagonal between the two points equals 5 feet, the corner is square. Slide the line along the batterboard to square it to the house. If the 3-4-5 method is too small for you deck you can use multiples such as 6-8-10 or 9-12-15, follow the pattern and you can use it for any size deck.

Next measure along the mason's lines from the ledger and lay out the center of the posts with strips of masking tape. Stretch the mason's line across the taped points to batterboards a foot or so past them. Make sure the line intersects the tape markers, then level it, and tie it in place. then adjust the line for square using the 3-4-5 triangle principle.

Next you need to mark the center of each post hole, drop a plumb bob to the ground from the intersecting powdered chalk. Mark the position of the lines on the batterboards and untie them. Leave the batterboards in place so you can use them later. When you get done it will look like complicated grid but trust me, taking such care at this stage will guarantee success down the road. Your layout should be complete and now you can move on to digging your footings.

Digging for footings and piers is about the least fun and exciting part of building a deck but it must be done so here is how I do it. At the marks you created for the post holed, dig down 6 inches deeper than the frost line in your area. Simply go on-line and check out a frost line chart for the region you live in. Make the holes about 12 inches wide at the top and 18 inches wide at the bottom. A gas powered auger can be used to dig the basic hole but you need to go back and hand dig the remaining parts, such as the wider areas at the top and bottom. If your setting your post below grade or the soil drains poorly, dig an extra 4 inches deeper. After digging your 4 extra inches add some gravel to the bottom 4 inches and tamp it down to create a drainage system. This is in extreme cases of standing water or really damp areas. Redwood, cedar or treated lumber will resist this water damage for many, many years. After that simply pour your concrete in the hole and make sure everything is level and square.

Well, you have done the half the hard part, digging. You still have some digging to do but at least you have an idea of what your deck will look like. Setting up the deck build is always hard but when you start laying your decking you will be happy that you took the time to get this part right. Your next step will be to pour your piers and install your posts.