Things You'll Need
Lattice sheets (wood or plastic)
1 5/8-inch galvanized screws
3/4-inch galvanized washers
2-by-4-inch seasoned planks (8-foot)
Lattice enclosures under decks serve two purposes. First, they create a storage space for garden tools, etc. Secondly, they can enhance the aesthetic look of a deck and garden area. Generally there are two types of lattice: plastic and wood. Plastic has the advantage that it doesn't need to be stained or painted, but decide on the color wisely (white or brown are common) as it can't be changed without replacing the lattice itself. Wooden lattice can be stained/painted, but will require painting/staining down the road after installation. Also consider cost. Wood lattice is generally less expensive than plastic (both come in 4-by-8 foot sheets), so calculate how much you'll need before starting the job.
Decide whether you are going to hang the sheets of lattice horizontally or vertically under your deck. If your vertical posts supporting the deck are 8 feet apart, it makes sense to hang them horizontally. Connect the top side of the lattice first to the existing frame of the deck, using a spirit level to make sure it is level before installing it (use 1 5/8-inch galvanized screws, and 3/4-inch galvanized washers, every 8 inches). Attach the two ends of the lattice to the posts with the same screws/washers, the same distance apart.
Install a 2-by-4 inch seasoned plank horizontally at the bottom of the lattice, so half the plank is covered by the existing lattice, and the other half is covered by a second piece of lattice. Screw the lattice to the plank. Connect the two ends of the 2-by-4 plank to each post with 3-inch 12d galvanized screws. Only make the bottom side of the 2-by-4 plank flush with the bottom side of the lattice if no second piece of lattice needs to be added.
Use a chalk line to mark the lattice if it needs to be cut. If the deck is on a slope, you will probably have to cut the lattice at an angle to accommodate the slope. Simply measure from the top of the horizontal deck frame (or bottom of the installed piece of lattice) to the concrete footing of the right vertical post, and then measure the distance to the concrete footing on the left vertical post. Mark these two measurements on each side of the piece of lattice--remember it will be installed horizontally--and run a chalk line between the two markings. Then cut the lattice along the line with a power saw.
Paint or stain your lattice after it has been installed.
Install one complete section of lattice--the area between one vertical deck post and the next--before moving on to the next.
Remember that where there are joins between two pieces of lattice--or at the bottom of the lowest piece of lattice in each section--you will need to install 2-by-4-inch planks. This will help strengthen the structure of the lattice, as well as the deck. Use seasoned 2-by-4-inch 8 foot planks as they are less prone to rotting. You can choose to paint them the same color as the deck, but they won't be seen from the outside.
Wear work gloves when installing any seasoned wood.