10×10 ft platform deck plans

Parts

Cut list

Kerf 1/8″ included. Every cut runs edge to edge.

Steps

• Tape measure
• Speed square
• Pencil
• Drill/driver
• Clamps
• Safety glasses
• Hearing protection
• Dust mask
• Circular saw or miter saw
• Sander, 120 and 180 grit

Underlined words have a short explanation: hover or tap them. All of them are on the glossary page.

1. 1Before you start

   Read every step once, start to finish, before you buy or cut anything. Each step names the parts it uses by letter; the parts list gives their sizes.

   Set up somewhere flat with good light. A pair of sawhorses with a sheet of plywood on top makes a fine work table.

   Wear safety glasses whenever a tool is running, hearing protection for saws, and a dust mask for sanding and for cutting treated wood or sheet goods. Tie back long hair and loose sleeves. Keep children and pets out of the work area.

   • Tip At the store, pick straight boards: hold each one up to your eye and look down its length. Skip boards that bow, twist or have big knots near the ends.
   • Tip Measure twice, cut once. Most mistakes are a misread tape, not a bad cut.

2. 2Cut and label the parts

   Cut every part on the cut list. Cut the longest parts first: if one goes wrong, it can still become a shorter part.

   To mark a cut, hook your tape on the end of the board, make a small V with its point exactly at the measurement, and draw a square line through the point with a speed square. Put an X on the waste side.

   Cut on the waste side of the line, so the blade's kerf (about 1/8″) comes out of the scrap, not your part.

   Write each part's letter in pencil on a face that won't show, and stack the parts by letter.

   Sand the faces before assembly while they're flat and easy to reach: 120 grit, then 180.

   ✓ Lay the parts out and count them against the parts list. Measure a few: if one is off by more than 1/16″, recut it now.

   STOP. Let the saw reach full speed before it touches the wood, keep both hands clear of the blade's path, and never reach under a board you're cutting. Support long boards on both sides of the cut so the blade doesn't pinch.

3. 3Call 811 and check the spot

   At least 3 working days before you dig, call 811 (or use call811.com). It's free. They send people to paint or flag buried gas, electric, water and cable lines near where the deck will go.

   Check your property line on your survey or plot plan, and ask your town about setbacks, easements and whether this needs a permit.

   Pick ground that drains: not a low spot where puddles sit after rain, and not over a septic field.

   STOP. Don't dig until the marks are down. Hitting a gas or power line can kill you and is expensive to repair.

4. 4Mark out a square rectangle

   Hammer a stake at one corner of the deck. Measure 120″ along the long side and hammer a second stake. Tie mason's line tight between them, a few inches off the ground.

   For the first square corner, use the 3-4-5 rule: from the first stake, mark 3 ft along the string. Run a tape 4 ft out roughly at 90°. Swing it until the 3 ft mark and the 4 ft point are exactly 5 ft apart. That direction is square: set a stake 120″ out along it.

   Measure the last corner from the other two (120″ and 120″) and set the fourth stake. Run string around all four.

   Measure both diagonals, corner to corner. Nudge the stakes until the two numbers match.

   • Tip For bigger layouts use 6-8-10 instead of 3-4-5: the bigger the triangle, the more exact the corner.
   • Tip Batter boards (two stakes with a crosspiece set 2 ft outside each corner) let you take the strings down to dig and put them back in exactly the same place.

   ✓ Sides are 120″ and 120″ and the diagonals match within 1/2″. Spray marking paint along the strings, then pull the stakes you're about to dig around.

5. 5Set the deck blocks

   Mark 2 rows of blocks running along the width: the front row 12″ in from the front string, the back row 12″ in from the back. Each row gets 3 blocks, 48″ apart, the end ones 12″ in from the sides. That's 6 blocks.

   At each mark, dig a hole 16″ square and about 6″ deep down to firm soil. Put in 2″ of gravel, tamp it hard, add 2″ more and tamp again.

   Set the block at the highest corner first, its top a little above the ground. Stretch a string from it across each row and level the string with a line level (a small level that hangs on the string).

   Set every other block so its top just touches its string: add or scrape out gravel under it. Each block's top should end up 4″ or so above the ground.

   • Tip Firm, undisturbed soil under the gravel is what stops blocks sinking. If your heel sinks into the bottom of a hole, dig deeper until it doesn't.

   ✓ A level on top of each block reads level both ways, and a straight 2×4 laid along each row touches every block.

6. 6Build and set the beams

   Sight down each beam board and mark the crown (the side it bows toward) with an arrow.

   Lay two boards (A) face to face, crowns both up, ends flush. Drive 3″ screws every 12″ in a zigzag, near the top and bottom edges, from both sides.

   Set each beam on its row of blocks, dropped into the block slots, crown up. The slots hold it in line.

   • Tip A beam with its crown up flattens under load. Crown down, it sags more over the years.

   ✓ Each beam is level end to end (check with a 4′ level at both ends and in the middle), and the beams are parallel: equal distances between them at both ends.

7. 7Frame the deck

   Lay the two rims (B) side by side, ends flush, and mark the joist layout on both at once: a line every 16″ with an X on the side where each joist goes. That's 9 joists (C), 14 13/16″ apart on center.

   Stand the rims on edge on top of the beams, 120″ apart outside to outside, overhanging the beams by 12″ front and back.

   Set each joist on its X, crown up, tops flush with the rims, and drive 3 screws, 3″, through the rim into each joist end.

   Measure both diagonals of the frame and push it square. Then fix a hurricane tie wherever a joist crosses a beam, with the nails or screws its label names.

   ✓ The frame is 120″ × 120″, its diagonals match within 1/4″, and the joist tops are flush (run a straight board across them).

   STOP. Pressure-treated lumber: gloves and a dust mask for cutting, wash your hands before eating, never burn the scraps.

8. 8Lay the deck boards

   Start at the front edge with the straightest board. Look at the end grain: set each board so the growth rings arc downward, like a frown (bark side up). Boards cup less that way.

   Lay 22 boards (D) across the joists, 3/16″ apart: a 16d nail between the boards makes a handy spacer.

   Drive two deck screws into each joist, 3/4″ in from each edge. Predrill within 2″ of a board end so it doesn't split.

   Where a board bows, screw one end, then lever the board straight with a chisel or a bent pry bar against the joist as you screw across.

   Let the boards run long at the ends, then snap a chalk line and trim them all in one straight cut with a circular saw.

   • Tip Wet pressure-treated boards shrink as they dry. If the boards are soaking wet from the store, butt them tight with no gap; the gaps open up within weeks.

   ✓ Gaps are even when you sight down them, every screw head sits just below the surface, and the trimmed edge is straight.

9. 9Finish

   Ease every sharp edge and corner with 120-grit sandpaper so nobody gets a splinter.

   Sand all over with 180 grit, always along the grain (the direction the wood fibres run). Scratches across the grain show through stain.

   Wipe off the dust with a barely damp rag and let it dry.

   Outdoors, use an exterior finish: a penetrating deck oil or exterior stain, or primer and exterior paint. Leave cedar bare to weather silver if you like. If it holds soil for food plants, leave the inside unfinished.

   Let it dry for the time on the can before using it.

   • Tip Try your finish on a scrap of the same wood first: stain looks different on every board.