How to Expand a Deck > Handyman Club of America

POSTED BY: Mike Berger
May 19, 2009

A tiny deck can feel more like a prison cell than a playground, but that’s no reason to tear it down. Overhauling and expanding the existing structure is an obvious way to increase outdoor living space and a great opportunity to add creature comforts. And if you choose the right materials, you’ll be paroled from the drudgery of yearly deck maintenance. Although no two decks (or yards) are identical, most deck expansion projects involve similar challenges. Use our project as inspiration to generate your own ideas, and adapt what we’ve done to fit your needs.

Benefits beyond size

Overhauling a deck offers a variety of opportunities to improve your outdoor living environment. Though the most obvious goal is to increase square footage, it’s important to understand how you want to use that space. Do you need a larger expanse on one level for easier entertaining? Would you prefer the privacy of smaller, intimate sections on either a lower or upper level, or do you want a more gradual transition from yard to deck that you’d achieve by extending outward in step-down levels? With proper planning and design, any one of these configurations (or a combination of them) is possible.

Don’t be afraid to ask experts for help in answering design questions. Home centers such as The Home Depot’s design centers offer free help and can provide a list of materials and supplies based on your plan.

To envision how a particular design would work in your yard, mark the perimeter of the planned addition with stakes and string. Try different arrangements — you might be surprised by the results.

For example, for this project, we had planned to simply add a lower step-down level to the existing deck. But after analyzing our layout, we realized that even though we would increase the overall square footage, we wouldn’t be improving the deck’s livability because the addition would be broken up into too many small areas. By changing the design and raising part of the addition to the same level as the existing deck, we added square footage on the main level, where it was needed the most.

If you’re happy with the size of your deck, you can always improve the existing space to encourage your family to make better use of it. For example, by building an arbor over the deck as we did, you’ll provide welcome shade on hot summer days as well as create visual interest. Adding an arbor needn’t be hard; in fact, if you follow the design we used for our project, you can construct one in a little more than a day. Other additions that improve usefulness and overall livability include amenities such as built-in seating, benches and planters.

Even if your existing deck suits all of your needs, a renovation can make upkeep easier. By replacing the deck boards with composite or plastic decking materials, you’ll eliminate the time and money involved in treating, staining and repair work. For this project, we chose Eon decking for two reasons. First, its color and embossed grain most closely matched that of natural cedar. Second, it has ultraviolet inhibitors that the manufacturer guarantees will prevent the boards from fading, twisting, cracking or splitting.

No matter what your goals are, you should be able to devise a plan that will work with your budget. Pressure-treated framing members are relatively inexpensive — we spent a little more than $400 for this large addition. Depending on the decking you choose, you could spend anywhere from a few hundred dollars for pressure-treated 5/4 deck boards to a few thousand for a high-end alternative decking material The cedar for our arbor cost about $500, but you could cut the cost in half by using pressure-treated lumber.

The proper paperwork

Once you’ve identified the goals of your project and have drawn a plan, ask your utility companies to mark the locations of underground pipes and cables, and then apply for necessary building permits. Don’t wait until the last minute — when I filed for the permit for this project, I learned that I’d need special approval to use the materials I had chosen. (Because Eon decking is a relatively new product, some communities have not yet added it to their lists of code-approved materials.) Getting special approval can be time-consuming, so allow a few weeks. Your local building inspector will need to see product specifications from the manufacturer before he or she will sign off.

Once the building permit has been issued, you’ll face a number of required inspections. For this project, I needed a footing inspection, a framing inspection (before the decking was installed) and a final inspection. Requirements will vary according to local codes. A firm foundation

When expanding a deck, you’ll probably need to pour new footings. The number of footings will be determined by the size and design of your addition, but if the project requires more than one or two, consider hiring a contractor to dig the holes. And rather than hand-mix dry concrete, have a local concrete supplier deliver ready-mix concrete. You’ll probably need to cart the ready-mix to the holes in wheelbarrow loads, so have extra helpers and multiple wheelbarrows handy. Because I wanted some flexibility in locating the bolts that secure the post brackets, I waited to install them until the concrete had set and I had a chance to double-check my measurements. To secure the bolts to the concrete, I used a vinylester glass capsule (VGC) adhesive from Simpson Strong-Tie.

The VGC system is made of a two-component adhesive contained within a glass capsule. Simply drill a hole into the footing, drop the capsule into the hole and drive the bolt down through it. As the bolt descends, it breaks the glass and mixes the adhesive. Once the adhesive has cured, slip the post brackets over the bolts and tighten the nuts. Framework for success

Framing a basic one-level deck addition is not much different from constructing a new deck. If you plan to attach the deck addition to your house, you’ll need to install a ledger board for the new section. If necessary, cut away any siding that might interfere with the placement of the ledger board; then install flashing and attach the new ledger board in a manner that’s code-approved, based on the construction of your house. Because I was tying into a concrete block foundation, I used pairs of hollow concrete block anchors.

Once you’ve secured the ledger board to the house, attach the support posts, header joist and rim joists to form the basic perimeter of the addition. Because our framework rests on top of 6x6 treated posts, I first cut them to the correct height and then nailed them to the post brackets I had previously installed.

When installing new header and rim joists, you may need to modify the framing of your existing deck to accommodate them. With our project, the new header joist needed to share the same 6x6 post that supported the corner of the old deck. By cutting the old header joist from the rim joist and then shortening the header by 3 in., I was able to create a stable base for both the old and new headers. If necessary, use a wrecker’s bar or a specialized decking-removal tool to strip off deck boards and expose the underlying framing members.

How you attach the header and rim joists to the support posts can vary according to the design of your deck addition. Because the bottom edges of the framing members for the lowest level of this addition were slightly below grade, I was forced to forgo the mounting posts at those points and rest the framing directly on the concrete footings. The method you use will be dictated by the building methods used on your existing deck and by local codes.

Once you’ve secured the new header and rim joists, cut the rest of the joists to length, attach joist hangers to the ledger board and to the header and set the remaining joists in place.

To frame a step-down addition, follow the same basic procedure as for a one-level deck extension. Because the lower level of our project was a mere 6 in. down from the main level, I secured the lower-level ledger board to the face of the main-level header joist and to the support posts. After you’ve attached the lower-level ledger board, simply install the rest of the framing members as you did for the main-level addition.

Made in the shade

The arbor we designed for this project can work with almost any deck — just modify its overall dimensions to fit your needs. The keys to the structure are the paired 2x6 cedar uprights that sandwich both the deck joists below and the overhead beam(see Layout PDF).

To create these uprights, first cut eight 2x6s to length. Use 2-1/2-in. stainless-steel wood screws to attach two 5-1/2-in.-sq. spacer blocks cut from the same 2x6 material between each pair of boards. (The bottom spacer is permanent; the upper one is temporary.) Position the lower spacer blocks the same distance from the bottom of the uprights as the width of the joists the uprights will straddle. Fasten the upper spacer block 6 in. below the top of the uprights. Slide each of the assembled uprights down over the deck joists, and secure the uprights to the joists with 3/8-dia. x 4-in. lag screws. Use four screws for each upright assembly, and stagger their placement so that screws from one side will not hit the screws from the other.

With a jigsaw, cut the decorative profile on the two overhead 2x10 side beams. Set the back ends of the beams in place between the uprights; then lift the front ends into their respective slots. Check that the uprights are square, and then secure the beams to the uprights with two lag screws for each upright. Once the beams are secure, remove the temporary upper spacer blocks.

Cut the profile and notches for the 2x12 front beam — remove the waste from the notches with a chisel — and lift the beam into position. Again, check that the assembly is square, and then toe-screw the front beam to the side beams. Cut the 2x6 overhead lattice supports as you did for the front beam, set them in place and toe-screw them to the side beams. Then cut the 2x2s to length and attach them on top of the 2x6 overheads using 2-1/4-in. stainless steel screws.

All decked out

Installing the Eon decking required using hidden fasteners to attach the boards to the joists. Because hidden fasteners eliminate visible screw holes, they add to the overall elegance of a project, but most are time-consuming to install. It may take two to three times as long to install deck boards with hidden fasteners. Every brand of alternative decking will have its own instructions; follow the directions carefully, and check with your local code authority to be sure the brand you choose is approved in your municipality.

When replacing deck boards, look for ways that they can enhance the appearance of the project. Use breaker boards to divide a broad expanse of deck into smaller, more pleasing sections and to keep from having to butt deck boards together. Consider running alternating sections of decking at opposing 45-degree angles, or create patterns with the boards that lead the eye out toward the yard or other points of interest.

However, be careful not to create a busy or visually disturbing deck board pattern. With our project, for example, we initially considered installing all of the decking at a 45-degree angle to the house (as the original boards had been oriented). But the strong shadows cast by the latticework of the new arbor would have created an unpleasant pattern on the diagonal decking. So we opted to run the boards parallel to the house instead. The result of our careful planning is a useful, visually pleasing structure that provides increased room with decreased maintenance — a winning combination from any angle.

**Form a Foundation**
Step 1: Stake out the perimeter of your planned addition and mark the location of any new footings. Have all utilities marked before you dig.
Step 2: A Bobcat with an auger makes fast work of digging. The five holes for this project took less than 30 minutes.
Step 3: Use a hammer drill and VGC adhesive to fix the post base bolts in place. Once the epoxy has cured, attach the post bases and tighten the nuts (inset).
Step 4: Fasten the new ledger to thehouse — here we used Red Head wedge anchors designed for hollow concrete block foundations.

Framing Details

Step 5: To support the new header joist, cut the old rim joist from the existing header; then cut the old header back far enough to allow the new header to rest on the existing 6x6 support post.
Step 6: For our project, the header and end joists rest on 6x6 posts. The doubled header provides a strong tie-in point for the ledger board of the lower deck section.
Step 7: Where ground level interfered with post placement, we rested the framing directly on the footing. A pressure-treated spacer isolates the framing from the concrete. Silicone caulk cushions the deck boards.
Step 8: Use joist hangers to fasten the joists to the ledger board and to the header. Note both the old and new ledger board flashing.

Building the Arbor

Step 9: After attaching the spacer blocks to the 2x6s, drop the upright assemblies onto the joists and attach them using 3/8-dia. x 4-in. lag screws.
Step 10: To install a side beam, first set the back end in place; then lift the front into its slot. Secure it to the uprights with 3/8-dia. x 4-in. lag screws, and remove the temporary support blocks.
Step 11: Cut notches in the 2x12 front beam and set it in place over the side beams, flush against the back edges of the upright assemblies.
Step 12: Fasten the remaining overhead 2x6 beams by toe-screwing them to the side beams.

Installing the Decking

Step 13: To install the decking, begin by loosely attaching the T-shape clips that hold the first deck board in place. Eon deck boards are held in place via a T-shape clip that interlocks with the profile of the deck boards. Beads of silicone caulk — we used DAP brand— act as cushions for the decking.
Step 14: Tap the next deck board in place, loosely install new clips and then tighten the clips for the previous board.
Step 15: Fasten nailers to the joists wherever you plan to install a breaker board; then toe-screw the breaker board to the nailer.
Step 16: Install the fascia boards over the rim and header joists to conceal the cut ends of the decking.