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473 Posts
Discussion Starter · #1 ·
ok, I'm ready to build a riser for a 2nd row of seats. With some calculations (repeated a number of times tweaking a variable here and another there) and keeping the low ceiling height in mind, I've decided to make it 12 1/2" with maybe a 1/2" added when I carpet it (total of 13").

Some background -

Riser width - 7' 3"

The ceiling drops to 6' 4" at one end (vent ducts) so don't want the riser below it. And on the other side is a pillar (plumbing from the powder room). So really, I don't have the full width of the room available for the riser.

I'm hoping it will be sufficient to hold a 3-seater (which based on my current 3-seater it should just about suffice).

Riser height - 13"

Here's how I accomplish 13"
3/4" - bottom (spruce plywood - the kind used for sub-floors).
5 1/2" - height of a 2x6
5 1/2" - height of 2nd 2x6 (so I will have one on top of another)
3/4" - top (spruce plywood sub-floor)
1/2" - I hope I get this from carpet.


I picked up a simple design here (and modified for my requirements)...

Hope it's ok to put the link here but if not, feel free to remove.

The modifications include ...
Reducing the width to 87"
Reducing the depth of the bottom box to 71" total
Reducint the depth of the top box to 61" total
Including a plywood at the bottom

Inside the riser
Not sure what I can use the inside for. There's a lot of space although separated at app. 1' by studs. Maybe I can just fill it with Roxul to 6" and leave 6" empty?

More info

The basement is carpeted. I'm planning to place the whole thing on the carpet and match the carpet I use on the riser to something close to the existing one. That way, if I want to remove the riser later (say, when selling the house) I can easily do so.

Also planning to put baseboards on the riser to make it look as integrated as possible (but not sure how it'll look since the side will be carpeted and the baseboard will be on top of the carpet).

The plan

is to buy pre-cut studs and plywood and just screw it all together in place.

This is my first project of this kind and I'm a total newbie. All I've ever done with wood is put shelves on the wall.

The request

Any feedback, comments welcome. I look forward to hearing from more experienced and knowledgeable people than I.

Thanks for looking.

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473 Posts
Discussion Starter · #2 ·
Stud calculation (all 2x6)

The lower box - 87"(W) x 71"(D)

2 x 87" - these will be the front and back
8 x 68" - join the front and back studs app. every 12"

68" + 1 1/2" (of front 2x6) + 1 1/2" (of back 2x6) = 71"

The upper box - 87"(W) x 61"(D)

2 x 87" - these will be the front and back
8 x 58" - to join the front and back studs app. every 12"

58" + 1 1/2" (of front 2x6) + 1 1/2" (of back 2x6) = 61"

Step -
71" (lower) - 61" (upper) = 10"
Therefore, I will get a front step of 10" depth (which should be adequate?)

Calculation of Plywood(3/4" sheet 4x8)

Bottom piece (below the bottom box)
4 x 8 - cut to 48" x 87"
4 x 8 - cut to 23" x 87" (use the remaining 25" x 87" for top piece below)

Top piece
4 x 8 - cut to 48" x 87"
25" x 87" - cut to 13" x 87" (use the remaining 12" x 87" for step piece below)

Step piece
12" x 87" - cut to 10" x 87" (Can I leave it at 12" or 11" so the step overshoots the bottom stud by an inch or two - I've seen this in my house).

Is it reasonable to ask them to cut the 48" into 3 pieces of 23" and 13" and 10" (with 2" waste)? It saves me having to buy another sheet.

Approximate budget
This is a little rough and gathered generally from big box stores

20 x 2x6 Studs (with cutting) - app. $100
3 x 3/4" 4x8 Plywood (with cutting) - app. $100
12' x 8' carpet - app. $100
(using very cheap carpet - could go as high as $300 or $400 with better quality)
Hardware (screws and plates to join top and bottom studs) - app. $100
(H/w is pure guess since I didn't check the prices)
Roxul - $30

Total (cheap carpet) - app. $430
and better carpet - app. $630 or $680.

Do these calculations and estimates sound reasonable for a riser build.

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1,229 Posts
ok... since u're lonely :)

i would probably just go with 5/8" plywood for the floor. That will be plenty strong for your couch with people on it. Heck the subfloor of my 20 yr old house is only 5/8's and it's held fine.

Are u using 2 layers of 2x6? that seems like overkill in terms of cost, wood and structure... You could build it like a floating dock, and just add a step out front.

Build it on with four 4x4 feet at each corner, cut to 12" height, and add a perimeter out of it, and a step at the front.

Take a look at my floating dock, which is basically a riser on water..... the bottom half of yours would be hollow, instead of having styrofoam billets in it.


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473 Posts
Discussion Starter · #7 ·
Thanks for the feedback, guys.

Petee_C, in your design, is the whole platform just resting on the perimeter.

I guess my concern would be if that's adequate support for the couch with 3 people. It would reduce the build effort and wood costs if I could just lay the ply on the perimeter.

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1,229 Posts
Hi D2,

I suppose I should have said to build it like a 13" high deck. But I just built a dock last summer so a dock came to mind.

My suggestion is kinda to build it like a deck, elevated above the ground to 12 or 13" The plywood sides or fascia would just be decorative, so u don't see the frame.

The whole platform is supported by your 4"x4" legs. The legs are 12 or 13" tall.


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Discussion Starter · #9 ·
I started the assembly.

Decided to stay with the initial design after struggling a little to make Petee's suggestion work. Since I had decided to do it this weekend and hadn't had much time during the week to work on alternate designs, decided to just go ahead with what I had.

Fri evening, on my way back from work, got the studs and plywood. Had them all cut at Home Depot.

In hindsight, I'd have had the plywood cut across the middle to make them half as heavy and easier to move into the basement. Those 3/4" sheets are heavy and 4' x 7' 3" is too big and heavy for the narrow steps plus you have to turn.

I may also have gone a bit overboard in the hardware buying very sturdy plates (both corner and straight) and possibly using a few extra screws where a pro might have known they were not needed.

Started by laying out the bottom pieces, removing all the staples from the studs (really necessary? don't know so I just removed them), marking and pre-drilling all the holes and then screwing them in.

I only have a drill and not a driver but with the number of screws, I decided to use the drill as a driver. It has too much torque but with practice I got really good at keeping the pressure on the screw head and using really short bursts of power so the bit doesn't jump out of the screw.

Then I laid out the bottom plywood (2 pieces) and pencilled in the position of the studs. Again, pre-drilled and screwed.

That's where it's at right now.

Tomorrow, will put a few more screws on the ply in the middle to make it really non-wobbly and then turn it upside down so the plywood is at the bottom. Then I start on the top piece.

Forgot to buy the Roxul so at some point tomorrow will have to go back.

Working low on the floor takes its toll the back (at my age).

Total expenses so far - just under $300.

Still have to buy Roxul and carpet and I think I'll end around $450. When I had initally thought about doing this, I was hoping I could keep it down to around $200 but I now realize that was just wishful thinking.

This a first for me and I'm getting a real kick out it. I'm almost tempted to buy my own saw so I can do more projects but that's for another day. At this point with all the different kinds of saws available, I wouldn't even know which one to buy.

Will post the pictures tomorrow. Not many just a couple or so and they're still in the phone.

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473 Posts
Discussion Starter · #14 ·
Bottom piece in place

Decided to push the bottom piece in place and then assemble the top piece.

It's very heavy and if I didn't move it in place now I don't think I could push the combined weight of the top and bottom into place later. Makes it a little harder to work on the top piece but will see how it goes.


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Discussion Starter · #17 ·
Top piece assembled

Thanks, Paul_85.

I decided not to competely assemble the top piece. Rather I screwed in the studs to the rear stud and moved it into its final position. Then joined the upper and lower pieces. This way, I was able to line up the studs (top and bottom) because they had some play since the front stud was not screwed in yet.

Joining the top and bottom was the hardest part so far. I couldn't use the drill (not enough space between the studs) and had to manually screw in the plates.

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