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My brother owns a house built in the 50's or 60's. The patio for the house was made into a room an unknown number of years ago. The then-owners put asphalt tiles down. Some time after that, the then-owners put down a brown shaggy carpet. Through all of this, the original concrete "step" of the concrete patio remained.

(Fans of the era will recognize the style of the curve and the step.)

Flash-forward to modern day. He wanted to put down laminate flooring, but first needed to square-off the curve.

Step 1: rip up the carpet (in our case, exposing the asphalt tile)

Step 2: build out the curve into a step

Step 3: put down flooring

This Instructable is Step 2

Tools:

  • 6-foot straight-edge
  • 6-foot level
  • circular saw
  • drill with phillips screw bit
  • Ram-set
  • speed square or tri-square
  • saw horses
  • marker/sharper/pencil
  • saber saw with plywood blade

Materials:

  • Measure the maximum height of the cement step. Get enough 2xN (N = wide enough for the step height), 12 foot long
  • (2) tubes Liquid Nails
  • (20) 90 degree brackets (return what you don't need, or keep extra because they are useful)
  • (box) 1.25 inch wood screws phillips head
  • (box) 3 inch phillips head wood screws
  • (2) 4x8 3/4 inch plywood, one-side good
  • (box) ramset 22 short blanks
  • (box) ramset nails (minimum 1 inch, otherwise doesn't matter)

Step 1: Planning What to Do

The first thing to realize the patio is sloped to drain water. The second thing to realize the concrete is not square or flat. These are just facts of life.

The first thing you need is a baseline. We were lucky that whoever put down the asphalt tiles had put them square on the lower part of the patio - below the curve. We used a seam between two rows of the tiles.

If you don't have that, you can create a baseline from measuring from the back edge of the room (on top of the step, against the back wall). You want the baseline 1 to 1.5 feet past the farthest point of the step.(On the plan, at the bottom, this is the curve marked "IN". The line marked "OUT" is the baseline.)

Given the baseline, the first three measurements are

  • The width of the room at the baseline
    • (ours was 11 ft 1/4 inch)
  • The distance from the left edge, step base to baseline
    • (ours was 11 3/8 inch)
  • The distance from the right edge, step base to the baseline
    • (ours was 6 ft 2.5 inch)

The next measurements are the slope of the two edges to the baseline. See the two drawings at the top of the plan.

The left edge (in this case) is short - just under a foot. The slope a foot from the base of the step will be close enough for the slope a foot away.

The right edge is just over 6 feet. We have a 6 foot level. We overhung the level 4 foot, and made sure the 2 feet of the level was secure on the top of the step (one of us stood on the level while the other measured). At 4 feet, the drop was 6 5/8 inches. The drop at the step was 7 1/8 inches. (7 1/8 - 6 5/8 = 1/2 inch) at 4 feet. Half of 1/2 is 1/4. This means at 6 foot, the drop is (7 1/8 - 1/2 - 1/4 = 6 3/8). We rounded up to 6 1/2 (1/8 inches is well within the tolerance of this project).

Keeping in mind we were going to put 3/4 plywood on the top, we needed to subtract 3/4 inches from these measurements. Also, keep in mind we put the long "face" board on the outside, so we needed to take 1.5 inches from the edge boards. Thus, we needed three boards:

  • left edge: (11 3/8 - 1 1/2) x (7 1/2 - 3/4)
    • = 9 7/8 x 6 3/4 inches
  • right edge: ( 6 ft 2 1/2 - 1 1/2) = 6 ft 1 in long
    • with slope : (7 1/8 - 3/4) && (6 1/2 - 3/4)
    • = 6 3/8 && 5 3/4 ends
  • Header: 11 ft 1/4 in, slope:
    • (left) 6 3/4 in; (right) 5 3/4 in

Step 2: Assemble the Border

Critical: When you put the boards down, the cut edges of the boards need to be UP, not down against the concrete!! This maintains the square-and-plumb of the boards!!

First, just put the three boards down where they should be. The edge boards should be against the walls. The long board outside edge should be even with your baseline. If you get this wrong, the rest will be wrong.

This is very similar to building a deck, so we will call the long board the "header". The boards between the header and the concrete step will be the "rafters". We have the edge rafters already.

Starting at one edge, start marking, in 16-in increments, where the rafters will go. Number them. Look at the picture of the header and right-edge rafter. You can see the marks on the header.The actual first mark is 16-in from the wall. "X" marks where the rafter will go. "1" is the rafter number. You can see the "2" rafter with similar marks.

You should see 90-degree brackets in the pictures, attached to the boards and flush with the floor. Add your brackets now. The brackets on the header should be between where the rafters will be, on the INSIDE of the header (where they will not be seen with the top (or "deck") on).

Next, screw the edge rafters onto the header. Look at the pictures. Remember, cut edges UP.

Put the header/rafters in place. Using a sharpie, mark their outlines on the floor. The outside edge of the header should be your baseline. This is a sanity check you have the right measurements.

Move the header/rafters out of the way. Put a bead of Liquid Nails where the header/rafters will be (eg in the borders you drew with the sharpie).

Lower the header/rafters back into place.Make sure everything lines up correctly. Push down on the header/rafters so the wood pushes on the Liquid Nail bead. (smooth out any that are on the outside of the header).

Take the ramset, and put one or two nails through the holes in the brackets and nail them into the concrete. Don't worry if the nails are a too long; they just need to be shorter than the height of the header/rafters. The goal is to stop the header/rafters from shifting.

Your frame is ready to populate.

Step 3: Create a Cut List for the Rafters

Get some scrap 2x4 a few feet long.Look carefully at the picture of the header and right rafter. See the red marks in the floor, from the header and parallel to the right header? Note they are on the side of the header mark where the "X" is. This step is preparation for the rest of the rafters. Mark the floor for every rafter marked on the header.

Note you may need to measure from the right rafter to where the rafter should be, so the marks are parallel to the right rafter and the wall, and 90 degrees from the header. Remember, make the marks so the two lines are where the X is on the header.

Now, make a cut list. Each of the rafters will be different in length and slope.

First, measure the lengths of each rafter, from the header to the cement step. Since the step is most likely angled, use the shorter of the two. Don't measure exactly; 1/2 short is fine. There is a good chance the bottom angle of the step is curved and not a nice 90 degree corner. You do not want the rafter corner to be displaced from flat by that curve.

Next, measure the height of the header where each rafter will be. I called this the "OUT" measurement (because that end will be out into the room). Pick a name and stick to it.

Measure the height of the step where the other end will be. I called this the "IN" end. Once you have measured all of the IN heights, subtract 3/4 inches for the plywood. (Be careful and check your measurements and your math!!!)

Also, this is the place for a sanity check. Look at #4: the values are changed. The IN was originally 7 1/2, but that did not make sense, We were using 2x8, which is really 7 inches wide. All of the other IN - 3/4 inch values were 6 1/2 inches, and the original value was 7 1/2 inches. We went back and measured. Sure enough, it was off. We corrected the values.

We laid out all of the rafters and marked them with which end was which, and the number of the rafter. The drawing is the rafter after cutting to length, then cut the angle. Thee order is not important as long as you can safely hold the board and cut it. Saw-horses are very useful.

Step 4: Putting in the Rest of the Rafters

Remember - cut edge UP!! Pay attention to which way the ends go!! Make sure the right rafter is in the right place!

Lay the rafters out in the right orientation and order. Start with rafter #1! For each rafter:

  • First, put the rafter in the right place, See if it rocks because the concrete is bumpy. If so, you can mark the rocking point and cut a notch about 1/2 to 1 inch. Just make sure the notch does NOT come within 3-4 inches of the ends. You want enough "meat" for the ends and the spanning middle. Mark where the notch is on the floor so ypu do not put Liquid Nails on that part.
  • screw on the 90-degree bracket like you did for the frame
  • Put the Liquid Nail bead in the marked area
  • Put the rafter in place
  • Screw through the header into the rafter
  • Ramset through the bracket

Once all rafters are installed, take a break

Step 5: Putting on the Plywood Sheeting

If you marked the rafter locations from the wall, a 4 ft plywood will be exactly at the outer edge (eg resting entirely) on the rafter. Unless you add a scabbed 2x4, the next plywood "deck" will not have anything to rest on or be screwed onto. Look at the picture with the note about the scabbed 2x4, or the drawing. Since the scabbed 2x4 will hold weight, screw it to the rafter with a minimum of (3) 3-in screws, a maximum of 6-in apart.

NOTE: Make sure the top of the scabbed board is flush with the rafter! Use C-Clamps if you need to hole the scabbed board in place.

Put the plywood on the deck, edge against the wall. Start with the longest rafters. You can turn the plywood so the long side or the short side of the plywood is against the wall .. BUT .. the orientation should be such that, once the curve is cut, ALL of the plywood will be on the deck.

For example, the longest rafter + header was 6-ft 2.5-in, so the longest side was against the wall.

Either one plywood corner will touch the step, or the plywood edge will touch the step (for a concave cut), Measure from the non-touching corner to the step.

We just used a long piece of wood (our "scribe board"), made the mark for the touching corner to the step, and just made a bunch of marks, and "connected the dots" However, a better way is to make a "scribe jig" (drawing) and set the pen (sharpie) to the right position. To use the jig, first attach the pen (sharpie), ten position the jig s shown, and starting at one plywood edge, trace the curve while keeping the jig parallel with the raters (perpendicular to the plywood edge).

If you need to, use a big piece of cardboard, trace the curve, cut it out. After making sure you have the right curve, place it on the plywood and trace the curve.

Use a saber saw to cut the plywood. check the fit. When happy, cut the other end to be flush with the outer edge of the header. Screw the deck to the rafters You can use (2-4) 1.25-in screws to hold it in place.

Notice in one of the pictures a red mark on the step - that marks the center of the rafter. Using a straight-edge, draw the line n the plywood that is the center of the rafter. You will use that line for screws to secure the deck to the rafters.

Repeat as needed for the rest of the deck.

Step 6: The Finished Product

That is the finished extension! Clean up is "left to the reader" :^)

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