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Project Difficulty: Difficult
Estimated Project Time: 1/2 day

Tools and Materials:

Safety goggles
Hearing protectors (when cutting lumber)
NIOSH-approved dust mask or respirator (when cutting lumber)
Work gloves
Heavy-duty work boots
Measuring tape
Circular saw
Lumber for the joists
2 sawhorses (if needed)
Power drill and bits
3" deck screws or 16d galvanized nails
1-1/4" deck screws
Angle brackets
Tin snips
String, marker, and masking tape (to check for square)
Joist hangers
Galvanized joist hanger nails

Hurricane ties (if needed)
Strap ties (if needed)


For your new deck, once you have installed the ledger (if the deck is attached to the house), posts, footings, and beams, you're ready to hang the joists.

Joists usually are attached to the ledger on one end and a header joist or a beam on the other end. If you are building a freestanding deck, you'll need to install an extra beam instead of attaching a ledger to the house.


1 . Plan Ahead

When decking boards are not long enough to span the entire distance of the deck, you must butt two decking boards together.

It's common to make this butt joint on top of a single joist, but this can create problems. You'll need to nail or screw near the end of the decking boards, which can cause them to split. Plus there isn't much for the decking to rest on (even less if the boards shrink).

So to build an extra-sturdy deck, figure where your butt joints will be, and double up your joists at those places. (Fig. 1)

2 . Splicing Joists

If your deck is too long for a single joist, you'll need to join joists on a center beam. You can do this by either:

* Letting two joists overlap each other and joining them with 3-inch deck screws. The advantage of this system is that you do not have to cut the joists to length.

* Cutting each joist to exact length and butting their ends together, joining them with strap ties. (Fig. 2)

3 . Fasteners
Where it is possible--at the header joist, for example--you can attach the joists by backnailing, that is, by nailing through the face of the header into the end grain of the joists. Use 3-inch deck screws or 16d galvanized nails, three per joint. But joist hangers are preferred in all locations by most building departments.

4 . Hanging the Joists

For this project, you'll need an assistant to help you with certain steps. The instructions below are for a basic low deck that uses a ledger to secure the deck to the house.

Caution: Hire a professional to do the work if you want a deck that:

* is raised up high

* is cantilevered out from the house and supported by angled braces attached to the house

* is set in swampy or otherwise unstable soil

* is set on a slope

* is placed on a roof

* must support heavy loads, such as a hot tub

1) It is usually easiest to start by assembling the outside members into a box (Figs. 3 and 4). Assemble these carefully because they will probably be the most visible. Predrill for all screws or nails that come near the end of a board. If your outside joists sit on top of the beam, attach them flush to the ends of the beam.

At the corners, join the header and outside joists with 16d galvanized nails or 3-inch deck screws, driven through pilot holes. Reinforce these joints with angle brackets attached to the joists with 1-1/4-inch deck screws. You can make your own angle brackets by cutting joist hangers with tin snips (Fig. 5).

Check for square, using string and a measuring tape. Mark measurements along the string with masking tape and a marker, if needed. You are now for the first time testing the shape of your finished deck surface, and it is not too late to shift things around a bit.

2) At each joist location, install a joist hanger (Fig. 6). You should use galvanized joist hanger nails, but first you may want to tack the hanger in place with 1-1/4-inch deck screws.

Lumber can vary in width as much as 1/4 inch; if you have to move a joist hanger, it's easier to remove a screw than a nail.

As you started your deck, before the joist stage, you should have already marked both ledger and header with vertical lines for joist positions. Also, there should be Xs to indicate on which side of each line the joists will be installed. (Note: Placing joists on the wrong side of the line is a common mistake. Make sure this X is on the same side of the line for both the ledger and the header.)

Now, take a short block of joist material and hold it in place against the ledger or header: it should touch one of the vertical lines and cover the X, but most importantly, its top edge must be flush with the top of the ledger or header. Slide the joist hanger up against it so that it touches on one side only. There are pointed tabs on the hanger; pound them in, and they may hold the hanger in place. Drive two nails in to hold the hanger in place.

Double-check to make sure the block is still accurately in place, and then close the hanger around it and fasten the other side with the recommended number of hanger nails.

At the inside corners of your "box," install angle brackets.

3) The joist ends must butt against the ledger or header tightly at all points. So before you measure for cutting the joists, make sure the end you are measuring from is cut square. (Sometimes the lumberyard will give you ten that are square-cut and one that isn't, so look at them all.) Cut the joists to length.

Right now you're probably itching to make some real, visible progress in a hurry. But first take a little time to seal the open grain of the cut ends with some sealer/preservative.

Install each joist crown-side-up (Fig. 7). This is a two-person operation. If things are tight, you may have to slide both ends down at the same time. A little pounding is fine, but if a joist is so tight that it starts to bend, take it out and recut it.

If you have the kind of flashing that makes a 90-degree turn to cover the face of the ledger, just smash the joist into the flashing. But if your flashing makes only a slight downward turn, there are two options: slide the joist under or smash it in and bend the flashing. Ask your inspector which is best.

4) Eyeball the framing to see that everything looks straight and parallel. Finish installing the screws or nails in the joist hangers--put one in every hole. Where joists rest on a beam, toenail or drive a screw to minimize twisting. Hurricane ties provide extra strength but are not usually required by code. (Fig. 8)