How to build a Deck Around a Tree

You might have happy memories of playing and dreaming in a treehouse as a child. Now that you're older, why not build a deck around a tree in your yard to bring back those good times?

Trees give great shade that will keep you cool on days that are too hot to handle. Still, there are a few more things to think about when building a deck around a tree. If you plan well, you can build a deck around almost any tree structure.

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How to Build a Deck Around a Tree

Your backyard deck around the tree is similar to any other deck. Except for the peculiar framing required to build a support frame around the tree, the technique of building the deck remains the same. Never, ever attach deck framing to a tree. At all times, your new deck must be separate from the tree.

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Materials and Tools Needed

You’ll need all the ordinary materials for building this deck. The list really is the same for a normal deck:

• Concrete

• Anchor bolts

• Post bases

• Through bolts

• Support columns

• Beam material

• Joist hangers

• Structural screws for hangers

• Joist material

• Decking material

• Stair and Handrail material

• Special Deck Post hardware and through bolts

• Flashing for the ledger board

Here’s a fairly inclusive list of many of the tools you’ll need:

• Shovels, picks, spud bars, and post-hole diggers

• Wheelbarrow

• Garden hose

• Builder’s level, transit, or a laser level

• Ladders and/or pipe scaffolding

• Assorted levels

• Hammers, ratchets, sockets, open-end wrenches

• Gloves and safety glasses

• Knee Pads

• Circular, reciprocating, and mitre saws

• Hand saws

• Belt sander

• Cordless drills, drivers, and assorted bits

• String

• Chalk line

• Framing square

• Carpenter pencils

• Sawhorses or portable workbenches

• Job-site table saw

Step 1: Assess your trees

Make use of the notes from your consultation with the arborist to ensure you do not hurt the tree. You should have ideally used a voice-recording app on your phone to record all of the comprehensive advice you paid for during the meeting.

Don't be afraid to highlight any danger zones or areas where the arborist has advised you not to dig. Trim the branches that are easily reachable from the ground if the arborist directed you to do so. Once the deck is finished, you can nearly always install a step ladder to allow you to trim large branches. Overreaching for branches that may fall and knock you off a ladder is not a good idea.

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Step 2: Plan your deck

Before meeting with the arborist, you should have established a deck layout. It's possible that his advice called for a few changes. The most significant component of the idea is how you establish an easily adjustable, ever-expanding box or octagon around the tree's trunk. Any and all joist hangers should be fastened with structural screws that are easy to remove years later when the opening around the tree has to be extended.

It's a good idea to plan ahead 20 years. Long joists three or four feet away from the tree may be doubled, as these distant joists may begin to serve as load-carrying beams for the box that surrounds the growing tree. It is significantly easier to build these extra joists now than it is to do so later.

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Step 3: Outline & Prepare Deck Site

Your deck foundation pier arrangement is no different than any other deck installation that does not incorporate a tree. Keep the soil under the tree from becoming compacted. The arborist undoubtedly discussed this during his or her visit.

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Step 4: Dig Post Holes

Because of the tree roots, digging the holes for the deck piers may be difficult. A reciprocating saw with a demolition blade is ideal for cutting tree roots. Contacting the dirt around the roots should cause no harm to the blade.

To dig tight clay soil, consider utilizing a rotary-hammer drill instrument equipped with a larger flat tiny shovel spade. These tools are similar to miniature jackhammers, and the flat spade bit can quickly bite into the clay and remove chunks.

Step 5: Measure, Cut and Place Posts

You can measure the height of any support posts with a builder's level, transit, or laser level. It's ideal to utilize 6x6 posts with an L-notch at the top where the deck's support beam will sit. Attach beams to the side of a post if all of the weight of the deck above is concentrated on two small semi-circles of the bolt that runs through the support column.

To connect the support columns to the concrete deck piers, always use certified metal post bases. The post bases should be at least 4 inches above the soil line. Make that they are rated for extreme exposure to modern treated lumber with a high copper content.

Step 6: Install the Ledger Board

The beam attached to the side of a house to which the deck joists are joined is known as a ledger board. It is critical that the ledger board be joined to the house with through bolts rather than lag bolts. Furthermore, the ledger board should be adequately flashed to prevent moisture penetration and deterioration. Small 1.5-inch triangle fire cuts should be made in the tops of the deck joists so that the flashing can lap over and down onto the front face of the ledger board. Make sure the flashing has a kick out so that all water drips to the ground below.

Before attaching the ledger, a secondary flashing must be installed on the house wall. This flashing is installed over the home siding or brick to keep water from entering the house framing and sheathing. Special metal connectors should also be erected and attached with through-bolts to connect the deck joists to the house joists, ensuring that the deck never pulls away from the house.

Step 7: Frame the Deck & Install Joists

Attach the deck's outer frame first, square it up, then install temporary diagonal braces to keep the frame square while the joists are installed. After all of the joists have been set, it might be difficult to square up the undercarriage, which can weigh close to 1000 pounds or more.

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Step 8: Frame Around the Tree

An enclosure must be erected around the tree to allow for at least five years of growth. To make an octagon out of a square box, you'll probably need to install 2x6 diagonal joists. Because most people would never stand directly up against the tree, the decking material can overhang the structure by an inch or two. Their feet would be 9 to 12 inches away from the tree trunk.

This decking can then be trimmed as the tree develops each year. At all times, leave a 1-inch gap between the tree bark and the decking. The box joist hangers should be fitted with structural screws to enable for simple removal and expansion of the box as the tree grows. As previously said, double up primary floor joists away from the tree that would eventually accept beams that will build a larger future box.

Plan ahead of time so that all of the screws used to construct the box may be retrieved when the tree grows

Read more:  How To Build an Octagon Deck

Step 9: Mark for Tree Cuts and Lay Deck Boards

The decking installation is simple. Read the installation instructions for the decking material. For a professional appearance, scribe an irregular shape into the decking that fits the outside diameter of the tree trunk at that spot.

Make the cut using a jigsaw, following the scribed line on the decking. Maintain a minimum of 1 inch of space between the decking and the tree trunk once more. If you anticipate the tree swinging in strong gusts, you may need to increase the distance.

FAQs and answers about Building a Deck Around a Tree

Do I need permits or an arborist before I design around a tree?

• Yes. Most cities require a building permit for decks, and many also enforce a Tree Code (separate from the building code). Start by checking local permit pages and tree rules, and have an ISA-certified arborist define the tree protection zone in your plan set.

How much space should I leave between the trunk and decking?

• Leave at least 1 inch (25 mm) all around the trunk—and more if you expect sway or fast growth. Design the opening so you can enlarge it later without tearing up the frame. 

Should I attach any framing to the tree?

• No. The deck must be structurally independent. Attaching hardware to living trunks creates wounds and maintenance risks; arborist groups advise against fastening objects to trees.

How big is the “no-dig” root protection zone (RPZ/CRZ)?

• Common standards set the radius to 1.0–1.5 ft per inch of trunk diameter (DBH), with a minimum ~6 ft in many municipalities. Example: a 20-in DBH tree → 20–30 ft radius. Fence this area during construction.

Can I cut roots to place footings?

• Avoid it—especially >1 in diameter. If absolutely necessary, work outside the RPZ, expose roots with air tools/hand tools, and make clean cuts under an arborist’s direction; never trench or compact soil in the root zone.
  

Where should posts/footings go if the tree is in the footprint?

• Place footings outside the RPZ and span over roots with beams. Keep grade changes and heavy equipment out of the RPZ to prevent de-oxygenating the soil; if grades must change nearby, use retaining edges to keep original grade around the tree.

How do I frame the opening so it can grow with the tree?

• Build a removable box or octagon around the trunk using joist hangers fastened with structural screws (easy to remove later). Scribe and jigsaw-cut boards to the curve, and plan to trim the decking back as the trunk expands.

What’s the right construction sequence to protect the tree?

• Arborist first → fence the RPZ → set posts/footings outside RPZ → frame deck as an independent structure → scribe/fit the opening last. Keep crews, stockpiles, and machinery off the RPZ to avoid soil compaction, the #1 tree killer during construction.

Any material or detailing tips around the trunk opening?

• Use removable trim, keep a cleanable gap (≥1 in), and expect debris—plan for access to sweep/clear. For smoother cuts, scribe first and cut with a jigsaw; then ease edges with a router or sanding block.
  

How do I maintain the deck-around-tree over time?

•  Inspect annually: enlarge the opening as needed, clear debris, confirm the deck remains independent from the trunk, and monitor tree health (wounds/decay). The arborist’s guidance + the 1–1.5 ft/DBH RPZ rule should remain part of future modifications.