Math help!!! I have a slanted floor......

[gbondo9]

I have a room in my basement that will be my studio some day soon.

The floor is horribly slanted.

Here's the room details:

Its 14 feet long (or 168 inches)
Its 8.25 feet wide (or 99 inches)

The slope of the floor is as such: Its high at the back - low at the front - AND (looking forward into the room) it slopes from the right (high) down to the left (low end) as well.

From the back right corner --> to the front left corner is the greatest difference. It's 8 inches. I came to this number using a piece of (very taut) string and a string level.

So here's my question:

How many 80lb backs of Quickrete do I need to level out this floor. I have 10 bags downstairs right now - but thats not going to be enough.

Any ideas?

 

[gbondo9]

This might help (I got this off a concrete website): An 80 lb. bag provides 0.6 cubic feet of cured concrete.

 

[TexRoadkill]

The real question is how many Mexicans does it take to pour your new floor

 

[mshilarious]

Not really enough information, we would also need the left to right slope or the front to back slope. But a wild guess would be at least 20ft3 (1/4 of 8" fill). It could be twice that.

You should drop level chalk lines around the walls starting at the back right corner, and start fillin' at the bottom.

 

[gbondo9]

Not really enough information, we would also need the left to right slope or the front to back slope. But a wild guess would be at least 20ft3 (1/4 of 8" fill). It could be twice that.

You should drop level chalk lines around the walls starting at the back right corner, and start fillin' at the bottom.

I'll try to get those other dimensions tonight.

Can I pour the concrete in stages? Like 10 bags at a time - and then next week the same?

 

[mshilarious]

I'll try to get those other dimensions tonight.

Can I pour the concrete in stages? Like 10 bags at a time - and then next week the same?

Eh, that's a bit beyond my knowledge, although I'd fear the bond is not as strong. You certainly wouldn't want to put down a bunch of thin coats, so if you break it up, do it starting with the deepest section and put up forms so you can pour that section at one time. You can tie into surrounding sections done later with some steel reinforcement, you shouldn't need rebar, but that grid stuff used for garages, etc. Obviously I'm a bit out of my area here. Usually I just watch the contractors pour the slabs although I've done my share of posts . . .

 

[JuliánFernández]

The real question is how many Mexicans does it take to pour your new floor

Hey Tex, don´t you think that you can bother someone with that kind of answer?

 

[Seeker of Rock]

A rough estimate is 62 bags, using a very rough formula on some assumptions...assuming that the floor slopes evenly from 8" in two directions to 0", one direction 8" to 0" along an 8' run, the other 8" to 0" along a 14' run, and that you would not use a filler. It can be done more accurately with spot elevations, but if I were you I wouldn't go that far for what you are doing. Even though bags claim the cubic footage coverage they do, I always seem to get a higher yield out of them.

To save money, I would do this...if you have any scrap bricks or any concrete chunks or gravel, I'd definitely fill some of that 8" deficit with fill. 8" of concrete is way overkill for a floor (non-structural)...hell, it's even overkill for a driveway, and that's not including the 4" of existing floor you are pouring on top of at the deepest point. Typically, I spec pedestrian walks at a 4" thickness, usually non-reinforced since we don't have the freeze-thaw climate here in Florida, and I'm guessing this will obviously be a climate controlled room, so you wouldn't need it on an interior even if you are up north. Personally, I would think you'll be fine using even a thinner layer of concrete on top of fill on an interior since there is already a concrete base below(your current floor). You'll run into problems if you use concrete as the surface, though, when you reach about 3/4" depth or so, because of the size of the aggregate in the concrete...in other words, you won't be able to blend it down to 0" to meet the floor where it is straight. I would use a mortar coat maybe 1/2" thick all the way around on top of the concrete to give a final leveling course and it will smooth easily for a finished floor look.

Separate pours? Not a problem. As MS suggested, metal ties are the best thing to use between pours. Rebar would be an overkill unless you plan on pouring the entire 8" depth in concrete. You just want something to bind the separate pours together, and metal masonry ties (the thin, ridged ties you've probably seen laying on the ground around a newly constructed brick house) will work fine. Just shove some in, maybe every 8" or so, to the edge of the pour when you reach a stopping point edge for the day. I would definitely do a concrete base with a mortar leveling coat, though.

Sorry for the book.

 

[gbondo9]

Not really enough information, we would also need the left to right slope or the front to back slope.

OK - So looking forward in the room (which is 14' long and 8.25' wide), here's all the slope angles (Right back being the highest and left front being the lowest):

Right back to Right front: 5.5" slope
Right back to Left Back 1.5" slope
Right back to Left front: 8" slope

I've also attached a glorious mspaint representation.

 

[gbondo9]

A rough estimate is 62 bags, using a very rough formula on some assumptions...assuming that the floor slopes evenly from 8" in two directions to 0", one direction 8" to 0" along an 8' run, the other 8" to 0" along a 14' run, and that you would not use a filler. It can be done more accurately with spot elevations, but if I were you I wouldn't go that far for what you are doing. Even though bags claim the cubic footage coverage they do, I always seem to get a higher yield out of them.

To save money, I would do this...if you have any scrap bricks or any concrete chunks or gravel, I'd definitely fill some of that 8" deficit with fill. 8" of concrete is way overkill for a floor (non-structural)...hell, it's even overkill for a driveway, and that's not including the 4" of existing floor you are pouring on top of at the deepest point. Typically, I spec pedestrian walks at a 4" thickness, usually non-reinforced since we don't have the freeze-thaw climate here in Florida, and I'm guessing this will obviously be a climate controlled room, so you wouldn't need it on an interior even if you are up north. Personally, I would think you'll be fine using even a thinner layer of concrete on top of fill on an interior since there is already a concrete base below(your current floor). You'll run into problems if you use concrete as the surface, though, when you reach about 3/4" depth or so, because of the size of the aggregate in the concrete...in other words, you won't be able to blend it down to 0" to meet the floor where it is straight. I would use a mortar coat maybe 1/2" thick all the way around on top of the concrete to give a final leveling course and it will smooth easily for a finished floor look.

Separate pours? Not a problem. As MS suggested, metal ties are the best thing to use between pours. Rebar would be an overkill unless you plan on pouring the entire 8" depth in concrete. You just want something to bind the separate pours together, and metal masonry ties (the thin, ridged ties you've probably seen laying on the ground around a newly constructed brick house) will work fine. Just shove some in, maybe every 8" or so, to the edge of the pour when you reach a stopping point edge for the day. I would definitely do a concrete base with a mortar leveling coat, though.

Sorry for the book.

This is great! Thanks. I plan on laying floors down on top of this - so the appearance and smoothness of it is of little consequence (* I think).

I finally got all the angles up (see 1 post up) so it's definitely going to be less concrete that I thought.

To save labor and money - I'm also thinking now of doing 2 different levels in the room - with a step in between. Since I wont get to the "drum/tracking" room for another year or so - all the tracking will be done in this room - and I'm thinking now it might be kind of cool to separate my control area (desk. rack, PC, mixer, keyboard etc) with the back of the room where the gobos and guitarists will go.

What do ya think?

 

[Seeker of Rock]

Yeah, that's definitely less concrete you'll need now... cool!

I can chime in on the construction stuff, but I'm no professional on the mechanics of how the recording room should be laid out, just basic knowledge, but some of those much more knowledgable than I have usually suggested not to break up a room this size on the premise that it will be a much better environment for mixing, which is really going to determine a large portion of what your recordings ultimately sound like on other sources besides the control room. I'm sure there is no set rule, just repeating what I have previously read.

 

[gbondo9]

I have another adjacent room that will eventually be used for tracking (window into the control room and all) - but in the meantime - the only real separation that will occur in this room will be a 4 inch step in the middle. As far as the gobos are concerned - I want to make them so they attach to the ceiling/floor and fold out to "create" another space - which can then be folded back onto the wall to create a good mixing/listening space.

 

[TexRoadkill]

Hey Tex, don´t you think that you can bother someone with that kind of answer?

I apologize for leaving out the other ethnicities that are unfortunate enough to have to pour concrete for a living here in the states. That's hard work. But here in the southwest the Mexican immigrants have take over the construction industry. Should I be bothered by that?

My real point is that it's a lot of concrete and labor is cheap. Hiring a truck and a few guys who know how to do the job will save a lot of back breaking labor and hopefuly he won't end up with a floor that is all fucked up and have to hire somebody to break it up and pull it out and pour it all over again from scratch. Doing a patio slab yourself is pretty easy but trying to fill a grade in a home that you've invested most of your money in is another issue. So is the fact that the slope is there because whomever designed the basement obviously thought that drainage was an important issue. Getting rid of the drainage and filling it with expensive equipment is also something to be concerned about.

 

[gbondo9]

I apologize for leaving out the other ethnicities that are unfortunate enough to have to pour concrete for a living here in the states. That's hard work. But here in the southwest the Mexican immigrants have take over the construction industry. Should I be bothered by that?

My real point is that it's a lot of concrete and labor is cheap. Hiring a truck and a few guys who know how to do the job will save a lot of back breaking labor and hopefuly he won't end up with a floor that is all fucked up and have to hire somebody to break it up and pull it out and pour it all over again from scratch. Doing a patio slab yourself is pretty easy but trying to fill a grade in a home that you've invested most of your money in is another issue. So is the fact that the slope is there because whomever designed the basement obviously thought that drainage was an important issue. Getting rid of the drainage and filling it with expensive equipment is also something to be concerned about.

No need to worry.

I started the floor today. I decided to save myself some of the time and energy and do a step in the middle.

I used 25 bags today and me and a friend knocked it out in about 4 hours. Looks great and it's nice and level.

As for the drainage thing - it's not really a concern. My house is on a hill and only about 35% of the front of the basement is actually under ground (and even that's on a slope). The rest is actually above ground. I walk out the back room right into my back yard. I've never had a water problem down there (so far).

 

[Seeker of Rock]

I have another adjacent room that will eventually be used for tracking (window into the control room and all) - but in the meantime - the only real separation that will occur in this room will be a 4 inch step in the middle. As far as the gobos are concerned - I want to make them so they attach to the ceiling/floor and fold out to "create" another space - which can then be folded back onto the wall to create a good mixing/listening space.

Sounds like a great plan.

Wow, I'm glad to hear you knocked out 25 bags in a day! Hope you had a cold beer or six afterwards.

 

[gbondo9]

Sounds like a great plan.

Wow, I'm glad to hear you knocked out 25 bags in a day! Hope you had a cold beer or six afterwards.

We went through about 7 or 8 a piece during the job.

My back is feeling it today though. Kind of like a nice steak that has been pulverized with a sledge hammer.