New Railings for Old Decks
The fundamental steps for adding railings are the same as for building railings from scratch. If you want to modify an existing railing, use these instructions to install the necessary additional railing parts.
Some decks use a “through-post” design: The posts supporting the deck continue upward as part of the railing. Through-posts aren’t necessary on an existing deck unless you add a new elevated section and need support from the ground up. Railing modifications, however, may require additional posts attached to the perimeter joists or fascia.
notch the decking: Place posts— as evenly spaced as possible—every 4 to 6 feet. Mark the side of the deck for each post. If the decking overhangs, cut a notch so that the post can rest flat against the perimeter joist or fascia. Use a circular saw to cut as much as possible, an use a saber saw to finish the cuts.
cut and notch the posts: Cut all the posts to the same length. This usually will be the height of the railing, less 1/2 inches (if you install a 2x cap on top of the posts), plus the width of the perimeter joist and the thickness of the decking.
A post does not have to be notched unless it needs to match existing posts. Notch the lower section of each post: half its thickness and the length of the joist plus decking.
install the posts: Attach posts to the side of the deck with two lag screws or carriage bolts. Use bolts (bolts provide more strength) where you have a clear space on the inside of the joist. Drill holes while a helper uses a level to make sure the post is plumb.
Rails and Balusters
Whenever possible, purchase rail and cap pieces long enough so you will not have to splice them.
For more information on deck railings, see our rail deck section.
You can change the posts and balusters from the style of the existing deck, but it’s generally best to have the new design conform to the old one—unless the new space will be used for purposes completely different from the old snace.
Adding a Skirt
The underside of a deck can offer some difficult design challenges. Large green-gray pressure-treated beams can be distracting, and the ground underneath may become muddy. Plantings of hedges or shrubs—chosen carefully so their mature height will not be higher than the deck— are an excellent solution.
You also can “skirt the issue.” A well-built wood skirt may be the most visible feature of your deck. It will enhance the style of your deck and increase its utility by providing storage space. There are a number of different styles and material choices available for skirting a deck; installing latticework and solid lx stock are two of the easiest.
The skirt should visually cover up what is unsightly, but be sure the design allows air to circulate freely under the deck surface. If rainwater that seeps through the decking is not able to evaporate quickly, it soon becomes standing water—a breeding ground for mosquitoes.
More resources on the topic: http://www.diynetwork.com/how-to/updating-deck-railing/index.html, http://www.decks.com/deckbuilding/Deck_Railing_Designs
Provide a nailing surface for all parts of the skirt—top, bottom, and sides. If the below-deck posts are near the edges of the deck, you may be able to use them as part of the framing by running horizontal 2x4s between them.
Building simple framing: Screw vertical 2x4s to the outside of the perimeter deck joists down to about 2 inches above grade. If you want to install lattice panels (see opposite left), place the 2x4s where two sheets of lattice will meet; the edges need support. Next make a top and bottom frame. On the same outside face of the deck joist, fasten a 2×4 between the vertical supports with half its width exposed below the joist. Attach the bottom frame, toenailed to the vertical supports, plumbing the vertical members as you go.
Reinforcing the framing: A simple framing assembly is not very strong at the bottom. When you install the vertical 2x4s, place them next to a joist whenever possible. Joists on 16- and 24-inch centers should put the vertical supports at the lattice joints if you adjust the ends. Cut and miter (at 45 degrees) a 2×4 brace and screw it to the bottom of the vertical 2×4 and at the top to a joist or to the underside of the decking.
Installing a lattice Skirt
Lattice makes an ideal skirt material because it is decorative and easy to install, and provides plenty of ventilation. Use sheets of lattice that are at least }A inch thick, made of either redwood or pressure-treated lumber.
Cut and attach the lattice
panels: Cut the lattice so that all edges of the lattice panels will be supported by a framing member. Make sure the bottom of the lattice is about 1 inch above grade at all points (even pressure-treated lattice may rot if it sits in wet earth). Attach the lattice with 4d galvanized nails or l!/4-inch decking screws. If the lattice is brittle, drill pilot holes to prevent cracking it.
trim the corners and joints:
Apply trim to all exposed edges at outside corners and where the ends of sheets come together. At a corner, cut one piece of 1×2 and one piece of 1×3 to cover the lattice; install with galvanized screws or nails. Position the 1×2 edge to butt up against the 1×3, so the corner appears to be balanced.
Installing a Solid Skirt
Vertical 1x8s or 1x6s, spaced at 3/t-inch intervals, will hide the space under the deck more than lattice. They form a solid skirt that does not allow as much ventilation.
attach the boards: Starting at a corner, drill pilot holes and drive 2-inch decking screws to attach the boards to the top and bottom framing pieces. Use the thickness of a board as a spacer, and check about every fifth board for plumb. You may want to trim the corners as described for the lattice skirt.
Making an Access door
For storage or to provide access under the deck, make a door from three or four skirt boards. Tie the boards together with two horizontal nailers. Install flush hinges and an eyebolt latch. To make a lattice door, cut a section of lattice to size and trim the edges with 1x4s on both sides. Drill pilot holes and drive 1 /8-inch screws every few inches in an alternating pattern. Attach the hinge to the face of the 1×4.