How to Build a Curved Deck: Step by Step Guide [with Pictures]

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According to an old saying, every man must build a house, plant a tree and raise a son…. and build a deck 😉 I’ve planted a lot of trees, I have a son, I built a shed (it can count as a house), now it’s time to build a deck.

I didn’t just want any square or rectangular deck, I wanted something special. I’ve watched too much of the Decked Out television series on HGTV, so I wanted to build a beautiful curved deck. I wanted a challenge!

A deck is a place to enjoy the outdoors, an extra living and entertaining area. It enhances your house and lifestyle. A place to BBQ and watch the kids play in the yard. It’s a retreat you can build yourself. You don’t have to hire the professionals; you can plan, design and build it yourself. Are you up for the challenge?

How to Build a Curved Deck

Curved deck from top
Deck from side
Deck hand rails

Step 1: Create Deck Design and Layout

STOP! Before you start buying materials and digging up the ground or tearing out what might already exist; sit down, take a breath and do some thought work.

Everything begins with design and planning. I’ve seen a lot of decks, even helped someone build one, now it’s my turn. What do I want to use it for? Do I want ground level or elevated, or even multi-level? Square, rectangular or curved? Do I want a hot tub or spa on it? And the kicker; what’s the budget?

Careful planning is the key to building a safe and enjoyable deck. If there are kids and a spouse or partner in your life, involve them; you don’t have to listen, but it does make life easier.

Gather your ideas up, and then begin to sketch out your plan. The more thought you do before you pick up the hammer and saw, the less work you make for yourself.

Here’s my plan:

  • One-level deck
  • Connected to the house – ledger board is already installed
  • On the right side (looking out from the house) place for BBQ
  • Planning to add custom pergola so 2 post rails will be 8 feet high
  • Curve the left part of the deck as sitting area
  • Diagonal decking (changed later to parallel)
  • Decorative rhombus insert in the center

The plan makes the design. I know what I want; now I have the fun of figuring out how to build it.

As usual the fun begins by checking with the local Building Department and Homeowner’s Association about building requirements and permits. The Building Department usually is very helpful and provides information about footings, beams, guardrails, and stairs.

The building department should also identify if there are concerns regarding wind load, seismic issues, snow loads and soil conditions which may be unique to your location. They probably won’t say anything about lateral force support though.

If you’re planning on large gatherings on your deck or have kids who run, stop, jump and dance around, you may want to add diagonal bracing between beams and posts to control lateral movement.

You should also check for any underground utility lines (water, gas, power, communication, etc.). It’s a free call in North America to: One Call Referral Service (1-888-258-0808).

They’ll usually send someone to identify and mark out any concerns. It’s better to find out before you start if something is buried where you want to build your deck, then you can adjust the design if need be, or move your location.

Here’s my setup:

Footings

  • Concrete pilings at least 4’ deep due to frost issues
  • 12” in diameter to support more weight
  • Galvanized post base set into center of concrete piling

Support Posts

  • 6×6 pressure treated post will carry more than 4×4 posts and won’t require different size for tributary posts (posts that support middle of the beams and carry 2x the end post load)

Ledger Board

  • Mine was pre-installed by builder with flashing and metal wrap. It was mounted to the house rim joist approximately 4 3/4” below the bottom of the patio door to give protection from snow build-up, and easy access from the house.

Beams

  • 2 triple 2×10 main beams parallel to the house
    The first located 3’ from the house and supported by 2 posts
    The second locate 12’ – 6” from the house and supported by 3 posts
  • 2 double 2×10 beams angled between parallel beams and supported by 1 post where they meet

Joists

  • 2×10 pressure treated joists at 12” centers – the thickness of the plank is a rough indicator of what it can span in feet without support; 10” spans roughly 10 ft.
  • Attached at ledger board with metal joist hangers
  • Attach to beams with hurricane hangers or joist-to-beam straps

Joist Span

  • 13’-6” joist supported by 2 beams at 3’ and 12’-6”’ from the ledger board

Decking

  • 5/4×6 cedar decking

Railing

  • The deck will be about 4’ from the ground so railings are a requirement
  • 4×4 cedar posts anchored to the deck with blocking and bolts
  • Guard rails will be 38 inches high – the Building Department will tell you the minimums
  • Balusters will be installed so a 4-in. object can not pass between them.

Stairs

  • Pressure treated stringers on two 8” diameter concrete footings
  • Attached to the deck frame with metal brackets

With all these parameters I created deck design using Realtime Landscaping Architect

Curved deck design

Deck foundation design
Curved deck plan

Required Tools

Deck Building Tools

Step 2. Plan and Prepare the Site

Once you have the required permits and are ready to begin, it’s time to clear the building site. Construct four or 6 Batter Board frames and hammer them into location.

Use mason string or twine to outline and square the plan. The marking paint makes everything visible and marks the location of important building references. Make sure you triple check the location of all footings; they don’t move easily and they need to be centered under your posts.

Batter Boards

  • Batter boards are H shaped frames installed outside the corners of your build site. They are used with a mason string to outline and square your layout. A stake hammered tight to the house will serve the same purpose, but use batter boards for corners away from the house
  • Level the string as much as possible, and square it – the square root of sum of the length squared and the width squared should be the length of the diagonal between the start of one and the end of the other
  • Remember to mark the final string location on the batter boards so it’s easier to reattach should the string be moved or broken

Site Preparation

  • Remove any obstacles within the outlined area, and several feet outside it to. Then remove the sod and top layer of soil

Marking paint

  • A spray that can mark vertically and used to outline the build site
  • Mark the post hole locations with an X and drive a stake to mark the center of the post hole location

Stakes

  • A pointed 1”x2” length of wood used to mark corners, post hole centers, and other important building references.

Mason line

  • A no stretch string or twine used by masons and builders to identify level or straight line distances between reference points.

Footing locations

  • The string outlines and parallels your deck edge. Measure in from the string and out from the house to identify where each footing pier/post hole will be located
  • Make sure to double and triple check your measurements, you want the support posts centered on the footing and aligned with the beam it will carry

Stairs location

  • Mark in the stair location to align supports and footings/postholes. For my deck I’ll need two 8” footing/post holes to support the bottom of the stringer.

Deck planning and marking

Batter boards and mason string used to square the layout. Marking paint outlines the layout. The stakes are building references for footings/post holes.

Building site planning

Step 3. Building Deck Foundation

After making sure the marking paint and stakes were in the correct location, I was ready to dig the 6 holes. The deck will be attached to the house so the footings have to go below the frost line which is 4 ft. deep in my area.

I’m using 12” x 8 ft. sonotubes to line the holes. The 12” diameter provides a wider base to support more weight, and the tubes are easy to cut with a handsaw.

A little mental math: 6 holes X 4 ft. X 1 ft. (12”) = 24 cubic feet of digging. No problem. I began digging one of the 2 holes closest to the house.

It was hard packed sandy soil which had been partially backfilled and packed. The first 2 feet went fairly well, but the deeper I went the less power I had.

I was successful! One down and five to go; four of which were in fully undisturbed soil.

I went down to my local equipment rental company and rented a Motorised Hydraulic Auger with a 4’ auger and extension, and a manual post hole digger. The Motorised Hydraulic Auger is a cantilevered affair so most of the torque goes into the machine and not the operator.

Rented motorised hydraulic auger

I practiced on my hand dug hole; tidying it up and widening it at the bottom and going a couple inches deeper.

Digging for footings

The 5 holes went much easier. My soil is sandy loam clay with small rocks so the auger worked well. Make sure the holes are vertical to prevent frost from lifting against the concrete pier.

If your soil is rocky you may want a helper or two. The auger will still do the job, but needs more weight at the auger end to continue to drill downward. If you have bed rock closer than the frost line, then bedrock is how deep you go.

With the holes dug, I removed any loose dirt, and then packed down the bottom as best I could. I used the head of a sledge hammer reaching down the hole and tamping the bottom; more effective than a garden hoe.

You want the bottom to be flat so the weight of the deck pushes on a flat surface. To provide some drainage I also tamped gravel into the bottom the holes; making sure I still had a depth of 4 ft.

Adding gravel to the holes

The sonotubes went into the holes next. They’re easy to cut, light to handle, keep the concrete where you want it, and the smooth sides resist lifting by frost.

To make a straight cut on a round tube isn’t easy; I used the newspaper method (see Pro Tip). Make sure you level the top of the sonotube and that it is at least 4”s above the grade to keep wooden posts dry.

Installing sonotubes for footings

I used 1”x2” laid across the sides of the hole and screwed to the outside of the tube to keep them from shifting. Wooden wedges between the tube and the hole will work too.

Pro Tip:  To cut sonotubes make a template – tape together two or three pages of newspaper, wrap the sheet around sonotube. Keep the sheet snug. Tape the end of the sheet to itself. To mark the cut line just slide the sheet to the cut point.

Completed holes with sonotubes

Before filling the tubes with concrete, I cut 3 ft. lengths of ½” rebar. The plan is to push two pieces into each hole after they’re filled with concrete.

The rebar provides additional strength to the concrete and a better foundation for your deck. I used an angle grinder to cut the rebar, it was easier. I also prepared my favorite 6×6 adjustable deck supports so they were ready to insert into the concrete.

With everything ready, it was concrete time! I knew the 6 holes would take approximately 24 cubic feet of concrete, plus 2 extra for the part above ground level.

A cubic yard is 27 cubic feet (a cubic meter is 35.3 cubic feet), so having concrete delivered was going to be too expensive; there’s often a surcharge on small loads too. Bags of ready to mix it would be.

A bag usually does ½ a cubic foot, so I’d need approximately 52 bags. I chose the high strength which cures to 4000 psi in a month. The minimum for a footing is 2500 psi, but 4000 psi is recommended.

The instructions for mixing concrete are on the bag. You don’t want it too soupy or wet as it reduces the compression strength. If it’s too dry it can create fracture lines and air pockets which over time cause the concrete to crumble. It needs to be wet enough to slowly slump, but dry enough to stay mounded in the shovel.

I decided to rent a portable gas powered mixer ($50 for day) from my local equipment rental company. I could have mixed the concrete by shovel in a wheelbarrow, 2 or 3 bags at a time, but it would take longer.

Mixing concrete

Each footing would require a bit more than 8 bags, by mixing 4 at a time I could fill half a sonotube in two wheelbarrow moves. Don’t mix and move more than you’re comfortable handling.

I began with the two closest to the house and then the single one. After filling half a sonotube, I pushed the shovel up and down in the tube a couple of times to remove air pockets.

Once I had the tube full, I again used the shovel to remove any air pockets in the upper half, and then inserted the two rebar lengths.

Pouring concrete

After filling the first 3, I reset the mason line on the two closest to the house and inserted my favorite adjustable deck supports aligned with the string and centered in the tube.

Completed footing with deck support

I did the same process with the last three footings. I then cleaned everything up with the garden hose so the tools were as clean as before I started.

To help slow the surface drying time and prevent flaking or cracking, I covered each tube with damp fabric. I kept them damp for about 24 hours. The forecast was good so I didn’t have to cover with plastic, but was prepared if the weatherman was wrong.

After everything had dried, I removed the batter boards and cleaned up the site. I made sure the ground sloped away from the house; I didn’t want water backing into the basement.

I filled in around the sonotubes with dirt and covered with gravel.

Adding gravel around footing

I rolled out landscape fabric over the whole are the deck would cover, and spread a 2 – 3 inch layer of gravel over it.

Completed piers and adding landscaping fabric

My foundation for the deck was done.

Landscaping fabric covered with gravel

Step 4: Install Deck Posts

The posts to support my deck are pressure treated 6” x 6”, and provide a much stronger base than 4” x 4” material. The difference between buying 12’ and 8’ long material and cutting it for my deck posts is a saving of pennies a linear foot, so get what works for you. To determine my material requirements I needed a more accurate measurement.

I attached a joist hanger to each end of the ledger plate, measuring to ensure they were positioned properly. I then rested a 12’ plank in them, held the other end up until level, and measured down from the top of the plank to the base of the adjustable post bracket. This gave me a usable measurement to work with.

I knew the deck surface would be 4 ft. above the ground at the house due to the ledger board, and my measurement at the footing was 49”. I added an inch to the 49” for the deck board for 50”.

To determine the length I would need for my posts I did a little math. 1” deck board (5/4”) + 9 ½” (10” joist) + 9 ½” (10” beam) = 20” of structural material sitting on the post, so 50” – 20” = 30”. The adjustable post brackets allow for any final adjustment. I would need two 8 foot 6” x 6” posts to get my 6 posts.

Pressure treated material is often high in moisture content due to being immersed in a chemical bath. As wet lumber dries, it can twist, split, or check. Posts are often cut from the middle of a log so there are a number of things to look for when selecting posts.

After checking along the length of the post for curves and twists, look at the end grain. If the core or pith is in the middle at both ends, or close to the middle, it will dry straighter.

If there is no pith, look for grain (tree growth rings) that is close to parallel with one face of the post, it too will dry straighter.

I treated all cuts with a copper naphthenate–based preservative to protect the fresh wood, and to comply with the building code. I assembled the adjustable 6×6 deck supports and attached the posts to them using 2 ½” Simpson Strong-Drive Structural screws.

Installing deck support posts

Using a post level and braces, I leveled and secured the posts into position. I was now ready to build the beams.

Support post

Step 5: Install Deck Beams

Building the Beams

I needed to build two 3 ply 2×10 main beams 13’–2” long, and two smaller 2 ply 2×10 angle beams 70” long. Pressure treated dimension lumber usually comes in 12’ and 16’ lengths, but seldom 14’.

When selecting dimension lumber for beams always look for straight planks; a curve or twist is difficult to straighten. If the plank has a slight crown, it is acceptable.

Cut the planks to length, ensure all crowns are up, and nail or screw the planks together every 12” – 16” inches; some local codes also require carriage bolts to be used every 2’.

I also cut the exposed end of the beam at a 45 degree angle; aesthetically it looks better but allows water to drip off the beam easier. Remember to treat all cuts with a copper naphthenate–based preservative.

Deck beams

Beams for round part of the deck

I used self-adhesive bitumen membrane and tar paper on top of posts to prevent water rotting the posts, and covered the top of the beams with the membrane to protect it from moisture.

Flashing membraine

Post to beam connection

I covered the top of each post with self-adhesive bitumen membrane and tar paper to prevent water entering and rotting the posts. The membrane or tar paper also prevents the copper in the wood preservative from eating the zinc in the galvanized metal brackets. The new pressure treatment may be more environmentally friendly, but it eats the zinc up like a kid eats candy.

Where the beam would sit on the galvanized brackets I also covered with the self-adhesive bitumen membrane.

For beam to post connections I used Simpson ZMAX brackets and 2 ½” Simpson Strong-Drive Structural screws. The ZMAX is supposed to better resist outdoor and pressure treated corrosion.

Beam to post connection

How the beam is connected to the post is extremely important. The weight of the deck sits on the beams which transfers the force directly to the posts for support.

The connection has to keep the beam connected to the post, resist post and beam twisting, and prevent wind uplifts. The method I used places the beam centered fully on the post making for the greatest support.

Using correctly sized post to beam brackets helps prevent twisting of the beam and rotation of the post. I also used the stronger hurricane brackets to connect the joists to the beam, which also prevent twisting at the upper edge of the beam, and wind lift.

I also installed diagonal bracing between the posts and the beam. This creates lateral support and also helps prevent twisting. All decks that sit two or more feet above the ground should have lateral bracing.

Some Other Options:

The notched post to beam connection has the post notched half way across at the top making a chair for the beam to sit upon. Carriage bolts are used to connect the beam to the post.

The thickness of the beam determines the thickness of the post since it is better to have the beam fully supported on the post. A 2 ply beam is 3” thick and a 6X6 is 5 ½” thick, so notching out a rest for the beam leaves 2 ½” of the 6X6 for bolting the two together.

A 3 ply beam is 4 ½” thick which would leave no more than an inch for the connection, which isn’t enough; so a larger post would be needed. If a 3 ply beam is only partially seated on the notch, then the downward force isn’t fully carried by the post.

This can reduce the ability of the beam to carry the weight and cause a diagonal force against your post, causing it to fail. It is great for preventing the beam from twisting, but if the post rotates it can split under the notch.

On smaller decks a post sandwiched between two single planks bolted together at the posts is an option. It is great for preventing the beam from twisting and the post from rotating.

Remember to block between the planks that form the beam to prevent it from twisting. Also, the weight transfer for the connection creates a sheer force as it is carried by the bolts holding the planks to the posts.

The real problem is corrosion of the bolts by the copper in the pressure treatment causing the connection to fail.

Angle beam assembly

Assemble the two shorter 2 ply beams the same way as the large beams. I found it easier to mark the ends for angle cuts by resting them on the posts.

Treat the cuts and cover all connection points with the membrane before attaching the galvanized connectors. I used Simpson Strong-Tie ZMAX 18-Gauge Galvanized Framing Angles plus straps to secure the beams to the posts.

Angle beam assembly
Angle beam assembly from outside
Angle beam to post connection
Angle beam to post connection from inside

Adjustable deck supports allow for easier beam leveling.

Adjusting posts
Adjustable post base

Step 6: Build Deck Frame

The Ledger Board

The 2×10 or 2×12 ledger board attaches to the house at the rim plate, or to the concrete or brick foundation wall. Never attach a ledger board to brick veneer; it is usually only attached to the house with metal brick straps.

The ledger board is attached to a concrete or brick foundation using ½” concrete anchor screws. Predrill ½” holes in the ledger board, position it against the wall using temporary supports and ensure it is level.

Use a concrete bit and drill your holes every 18” to 24”. Bolt the ledger to the wall, attach and seal flashing above.

To attach a ledger to a house with siding requires a bit more work. Before removing any siding, make sure there is enough space below access doors to permit attaching the ledger to the rim plate and sliding at least 4” (8” is better) of flashing up under the siding.

Mark the siding to be cut and removed. Use a sharp utility knife and straightedge to make the cuts, trying not to cut the house wrap. Slide a flat pry bar up underneath to pop out the nails holding the cut siding and remove.

Install a 14” – 16” strip of galvanized metal where the ledger will attach. The bottom 2” should stick out below the ledger and be bent at a 45 degree angle as a drip edge.

Make sure the metal goes 8” behind the siding at the ends of the ledger. Caulk the upper edge, then cover with self-adhesive bitumen membrane to avoid water penetration into the ledger board as it provides self-sealing around nails and screws.

It also separates the metal from the pressure treated wood. Attach the ledger board using ½” lag screws. The last piece of galvanized material slides 4” – 8” up under the siding; it may need to be notched for the door and siding nails. The bottom 2” – 3” needs to be bent to sit flat on the ledger.

Pro Tip: Measure and mark the ledger board to identify where the joists will go before attaching it to the wall. That way the bolts attaching the ledger to the wall won’t be in the way when attaching the joists.

The Joists

The floor joists are the main support for the deck boards and give the deck its shape. The joists rest on the beams and connect to the house at the ledger board.

My ledger was pre-installed by the builder, so it was metal wrapped and flashed prior to the house siding going on.

I used 2×8 joist hangers to attach the joists to the ledger board. I spaced them every 12” which creates a more solid support than every 16”.

The 2×10 pressure treated planks were cut 13’-1” long. Wherever wood and metal would connect, I used self-adhesive bitumen membrane to avoid water penetration into ledger board as it provides self-sealing around nails and screws, and separates the corrosive zinc and copper combination.

I placed the joists in the hangers, resting them on the two beams. 2 ½” Simpson Strong-Drive Structural screws were used to connect the joists to the hangers. I measured the joist spacing on the beams, and used hurricane brackets to connect the joists to the beams.

I used tar paper to separate the joists from the brackets, and sealed all cut ends with copper naphthenate–based preservative.

Self adhesive membrane
Attach the joists to the ledger board with hangers and structural screws.

Hangers attached to ledger board
Floor joists
Attach the rim joists using concealed face mount joist hangers.

End joists

I connected the joists to the beams with Simpson hurricane brackets.

Joists to beam connection

I did a final deck leveling check and made sure that there was a slight slope toward stairs.

Step 7: Install Blocking Between the Joists

Joist blocking, or bridging, should occur every eight feet, or less. It reduces joist wobble and bounce, and helps prevent the joists twisting. The blocking should be attached flushed with the top of the joists.

I used the end scraps from my joists to reduce waste. I treated all cuts with copper naphthenate–based preservative to prevent rot.

Use a string line and snap a line perpendicular to the joists half way between the beams. Attach the blocking in an alternating pattern on either side of the string line mark to make nailing easier.

The spacing between joists should be the same, so you should be able to cut the blocks the same length. Rim joists however may be spaced differently and need blocks of a different length.

I also used blocking around the perimeter, or rim, of the deck to stiffen the outside joists and provide attachment points for the railing posts. A 3 point attachment makes a stronger and more stable railing than a 1 or 2 point attachment.

I did a lot of cutting (kudos to my DeWALT 12” Sliding Compound Miter Saw DWS780) to make all the blocks and used pounds of screws to attach them in place. The stable deck frame made it worth the extra effort.

Joist blocking

Curve framing

I spent a lot of time laying out the joists for the curved deck. I tried to keep the maximum distance between joist ends 12” at center.

To provide the maximum support I narrowed the distance by angling the short joists and attached them to the rim joist using metal angle brackets. That was the tricky part as some short joists were cut with an angle. I did a lot of blocking between the rim and neighbor joist to stiffen up the rim joist.

I found the center of the circle and attached a 1×4 board to the framing with a screw to mark the center. The drawing of the circle was really easy then.

To draw the circle I attached a string to the screw with a pencil at the end, and marked the circle on the joists. I used tape to make the circle more visible.

I cut the joists with a 7 ¼ circular saw. Some joists were cut at an angle. I then added more blocking to frame the outside of the circle and provide attachments for railing posts.

Deck curve framing
Round framing

Step 8: Install Deck Rail Posts

Cedar vs Pressure Treated Pine

The structural framing of the deck was made with pressure treated pine. I chose to use cedar for the posts and decking for several reasons.

Cedar will not twist when exposed to moisture and it has no corrosive chemicals to leach out. It handles temperature changes better than pressure treated material, and requires less maintenance to keep clean.

It is softer than pine, so don’t use a pressure washer to clean it; it will gouge it. Cedar is also resistant to rot so it doesn’t need chemical preservatives unless it touches the ground. If you decide to stain it, you’ll have to stain it every other year or so to maintain the color.

The major drawback to cedar is the cost; it is expensive. By building the support system for the deck with pressure treated pine I saved a lot.

The Posts

I used 4×4 cedar posts for the railing supports. Attaching them to the joists and rim joists with blocking and ½” hot dipped galvanized carriage bolts with washers and nuts.

I used two bolts and drilled the holes offset diagonally to provide more stability. Once all posts were bolted in place, I made sure the nuts were tight, and then covered the exposed ends with silicone to prevent rust.

All the railing posts were the same length, but final trimming was done after the decking was installed. The two 10’ long 4×4 posts that would support the pergola over the BBQ were extended below the joists and flush with the bottom of the beams. I screwed them to the beams for extra support and stability.

With the railing posts installed, I removed the temporary bracing. I angle cut and installed 4×4 diagonal braces between the outer beam and the support posts to prevent lateral movement.

Rail posts attached to joists
Post attached with bolts

After making sure the bolts were tight, I used silicone sealant to cover bolts and nuts.

Silicone sealant on bolts

The holes were drilled diagonally for better post stability.

Attached rail posts

The 10’ long posts were also attached to beams with structural screws for more stability.

Post attached to beam
Post to beam
Rail posts in the corner
Posts on circle
All rail posts installed
Center blocking

Learning Curve

I initially installed the blocking for the center divider decking boards and rhombus horizontally. It rained before I could install the deck boards and I realized the horizontal blocks had cupped due to the moisture and heat and were holding water. I removed the blocks and reinstalled them vertically.

I used pressure treated 2×4 horizontally for the blocking between the angled joists of the curved deck. They provide support for the deck boards and backing for screws.

Center and curve blocking

Step 9: Laying the Cedar Deck Boards

In preparation for installing the 5/4”X6” cedar deck boards, I coated the top of the joists with preservative. I then covered the top of the joists with 3” strips cut from rolls of tar paper. I could have used Shadoe Track or joist caps, but the tar paper does as good a job and costs a lot less.

Joist flashing
Deck flashing

To attach the deck boards I used a Marksman Pro Tool and CAMO screws. The CAMO system uses hidden side fasteners so there are no screws in the top of the deck. It also automatically keeps the space between deck boards. It worked really well.

In a perfect world all deck boards would be straight. To help straighten some of the deck boards I used a deck board straightener tool.

Installin decking boards

No screws are visible thanks to the CAMO system and the hidden side fasteners.

Installing decking
Installed deck boards

Bending Deck Boards

The most challenging part of the deck was bending the trim boards for the face of the curved deck. I used the Kerf bending technique to bend the boards.

Kerfing meant making cuts 1” apart and 2/3 of the way through the board; this removes enough wood material to permit the board to be bent without cracking or breaking.

I had 2 boards 10′ = 120” – 2 = 118 * 2 = 236 cuts and 2 boards 104” – 2 = 102 * 2 = 102 cuts; that’s 338 cuts! It’s a lot of cross cuts with 7 1/4 circular saw. Take your time; you want all the cuts to be perpendicular so the boards bend.

The cuts are 2/3 of the way through the 5/4 decking board, so they’re 24/32” deep. It takes the rigidity out of the board and allows it to bend around a curve.

I attached one end of the board to the deck framing while my wife was holding the board in the middle, I then slowly bent it and screwed it to each joist.

Curve deck boards
Curve boards installed

Step 10: Install Deck Railings

As I finished installing the deck boards my focus turned to the railings. The local codes dictate the minimum height the railing can be and the spacing between balusters.

For the straight top and bottom rails I used 2×4 cedar, and for the curved rails I used 2×6 cedar. The balusters are 32” x ¾” round black aluminum deck railing.

I planned out the spacing and layout of everything. The space between the deck boards and the bottom rail is 3½”, which makes it easier to push snow off the deck but too small for a child to crawl under.

The top rail is 38½” above the deck to prevent anyone falling off the deck. The balusters are 4½” apart at center, which makes the space too small for an infant’s head to go through. The railings would look great and be safe.

To make the curved top and bottom rail, I made a cardboard template which included the baluster spacing. I used a 7¼” circular saw to cut the cedar 2x6s into curved rails.

Finally, I cut all the railing posts at 40½” above the deck boards, and the pergola posts at 100½”.

Assembling the railing was easier than the cutting and drilling, but went easier with a helper. I installed the bottom rails, put the balusters in place, then lined everything up and put the top rail on.

I then covered the cedar posts temporarily with tar paper until I purchased the caps. To prevent the bottom rail from sagging I cut and installed supports halfway between the posts.

Deck railing
Hand rails
Curved hand rails

Step 11: Build the Deck Stairs

To plan the stairs I determined the distance between the deck surface and the ground. It was 49”. The standard for stairs is a run of 10” for every 7” rise, so I’d need 6 step stringers for my stairs. The 7th step is from the top of the stringer to the deck.

I used two of the 3 pre-cut pressure treated 6 step stringers I’d purchased to determine where the bottom of the steps would sit. I manually dug 2 holes for stairs footings, slid in the 8” sonotubes, and filled them with concrete.

To attach the 4×4 cedar posts for the stair and railing support I used Simpson Strong-Tie 4×4 ZMAX Galvanized Adjustable Post Bases.

To make the stairs I used 5/4×6” cedar planks. I used 2 trimmed pieces to make the 9¼” for each of the stairs, and one plank for the riser.

This would provide space for water and snow melt to drip off the stairs. The riser also prevents a child from getting stuck between the stairs.

The 3 stringers were attached to the deck using galvanized adjustable stringer connectors. The middle stringer makes the stairs more rigid. The two outer stringers were attached to the posts with ½” hot dipped carriage bolts.

Planning deck stairs

Simpson Strong-Tie 4×4 ZMAX Galvanized Adjustable Post Bases set into the concrete secure the railing posts.

Stairs footing

Used 3 pre-cut pressure treated 6 stairs stringers attached to the rail posts with bolt.

Stairs support

Galvanized adjustable stringer connectors attach the stairs to the deck.

Stringers hangers

Stairs – 9 ¼ from trimmed 5/4×6” cedar planks. Raisers – 7 ¼ from 5/4×6” cedar planks

Handrails

I used straight cedar 2x4s for the top and bottom rails and the ¾” round black aluminum for the balusters. The spacing was kept the same, but the holes for the balusters were drilled on an angle. With 40 holes to drill on the same angle, you may want to make or buy a jig.

Deck stairs

Conclusion

The deck is complete except for the pergola, but that’s another project. It looks awesome if I may say so myself, and is a great place to entertain and enjoy a relaxing BBQ.

My deck may also be considered freestanding since it is supported close to the house and by two beams; the ledger board isn’t load bearing. This may prove helpful in some areas due to local regulations.

Hopefully the Curved Deck has provided you with some useful information. Your comments are appreciated.

If you know someone who is thinking about building a deck, share with them if you liked it. Remember, you don’t have to hire the professionals; you can plan, design and build it yourself. Are you up for the challenge?

Want to build a beautiful cedar curved deck? This DIY tutorial with detailed step by step instructions will show you how to build a curved or round deck.

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