Drum "riser" over sloping basement slab

[masterofnone]

Hi all,

I've been an on-again off-again lurker on this fine site for a few years now. I've been slowly sifting through the wealth of information and advice both here and in Rod's book, with the eventual goal of building a small drum practice room in my poured basement. When I finally have my act together, I'll take the plunge and do a proper, formal, square-one introduction for the overall project.

For the time being, though, I have a question about building a decoupled drum riser over an uneven, sloping concrete floor.

The basic conundrum:

- The basement of my house, built in 1923, has a rectangular poured slab that slopes downward toward the center of the space and then again toward a sump pit/drain at one end. A laser level has it, at worst, perhaps 6-8" out of level, with the high points obviously around the perimeter, and the whole thing somewhat uneven besides. It is bone dry at all times, even through recent tropical storms. No cracks or apparent structural-integrity issues.

- The practice room will some day claim perhaps a 10' x 12' chunk of the aforementioned sloping floor, from one wall or corner downhill, as it were, into the middle of the space.

- I would just as soon use the slab as is...

- Unfortunately, **even putting future building concerns aside for the moment**, the floor is out of level enough, within the footprint of my drum kit, to make playing feel wonky.

- Basically, I'd like to have a "playable" surface in the short term, a buildable surface in the middle term, and a playable room in the long term. The first two mini-goals may or may not share a common solution.

- I had toyed with the idea of pouring just the space I'd be using for the practice room level, which would theoretically help with both ease of playing and provide a flat, level surface for bottom plates, etc. later on. This would of course reduce headroom throughout that whole area, possibly require hiring pro's (and having the $ to do so), potentially alter drainage for that portion of the basement, and so on.

- The other idea, especially applicable in the short term, is to build a drum riser, which might as well be decoupled. Pros: level surface for drums, headroom loss minimized to area of riser, various sonic advantages of decoupling drums from floor, minimized affect on drainage, minimal moisture/mold issues, much less permanent, less $, more DIY. Cons: Majority of eventual practice room floor spacee still uneven and out of level--building off of that would be a PIA later.

So, finally, here are my questions:
*I have read through posts regarding Glenn's riser--essentially layers of mass (mdf/ply/etc.) on top of rockwool, 703, or similiar; I have read Rod's description (p. 269) of a decoupled floor assembly (layers of GG'ed ply over rigid insulation over existing deck). I have also read Rod's section on sand-filled wooden decks (mine would be over slab, so minimal structural concerns).

1. If I'm building a max 8' x 8' riser over the existing concrete slab, how can I get it level? The aforementioned riser designs, and others I've encountered, basically assume you're putting your insulation and mass layers on a flat, level existing deck.

2. Rod's sand-filled deck (on an 8' x 8' scale) seems like it would allow me to rip sleeper joists to the contour of the slab, somehow secure them to the slab in decoupled fashion (Mason floor mounts? I have my doubts re: the utility of anything resembling a puck or u-boat in this case.), fill bays with sand, and top with ply. Is it wrongheaded of me to think that sand and hardware mounts are mutually exclusive ideas?--i.e. the sand would flow underneath any raised portions of the joists, or otherwise be difficult to contain within the bays.

3. I understand that decoupling and isolation are different animals. Various riser designs attempt the former; and the latter, while more directly addressed in Rod's sand-filled design, is something of a pipe dream when it comes to relatively low-mass wooden raised decks in general (and a moot point for me until I build an isolated room around said riser/deck) . Still, is there some way to combine the decoupled aspect of Glenn's design with the ability to have a leveled frame?

Sorry for the rambling and many thanks in advance for any and all assitance.

[masterofnone]

The obligatory week+ bump--and a preemptive apology if the original post committed some classic newbie blunder.

[Soundman2020]

Hi there "masterofnone" (love the handle!), and welcome to the forum!

I'm glad you "bumped". For some reason, your post wasn't on my line-up of threads to respond to! Must have slipped through the proverbial cracks...

1. If I'm building a max 8' x 8' riser over the existing concrete slab, how can I get it level? The aforementioned riser designs, and others I've encountered, basically assume you're putting your insulation and mass layers on a flat, level existing deck.

If you use Glenn's riser design, then you could just stack more layers of 703 under the "low" side, to bring it up to the same level as the "high" side. So, for example, make the deck big enough that you get a difference of exactly 2" (or 3" or 4") between the left edge and the right edge, then stack 4" of insulation under the left edge, 5" under the middle, and 6" under the right edge. That would give you a level surface. You could then cut wood skirts a bit shorter than that, at the same angle as the floor slope, if you wanted.

Another more accurate way would be to measure the exact angle of the slope, and cut a series of triangular sections from panels of 703 at the exact same angle, and glue those to the bottom of the deck.

That's how I would do it.

2. Rod's sand-filled deck (on an 8' x 8' scale) seems like it would allow me to rip sleeper joists to the contour of the slab, somehow secure them to the slab in decoupled fashion

For an actual studio floor, that would be an option, but I would not bother trying to decouple. Floating a floor is a major task, and very expensive, so unless you have a big budget, don't even go there. So you could just cut angled joists, bolt those to the floor, caulk, and fill with sand, then put a plywood deck on top.

the latter, while more directly addressed in Rod's sand-filled design, is something of a pipe dream when it comes to relatively low-mass wooden raised decks in general

Very, very true! You might find this thread interesting (if you haven't already seen it)...
http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

- Stuart -

[masterofnone]

Thanks so much for the reply and sage advice therein.

The shim/fill/level-it-out-with-pieces-of-703 idea makes perfect sense. I had wanted to stick to Glenn's approach as closely as possible, as it seems the most straightforward and elegant of any I was considering.

I'll leave pouring a level floor for another day (year).