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need help with a basement floor

hi! I;m working on a house that is being rehabbed. at the moment i am workin gon the basement floor. the house is over 100 yrs old, and the previous owners had some of the concrete pad jackhammered and tossed in a corner. there seem to be two layers to the pad: you have the dirt under it, then bricks, then the slab itself. about half of the bricks are disturbed, so i am re laying them, and will then pour concrete over it. would i need to use a self leveler to pour directly over the bricks, or can i just pour the concrete right on top of the bricks? its not a huge basement, roughly 8 ft by 20 ft.  also , about  how thick does the concrete pour need to be?  there is no weight on the floor slab, other than the furnace.

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Posted 2011-03-21T02:46:40+0000  by icabear3 icabear3

Hi icabear3,

 

Thank you for your question and welcome to the community!

 

It seems there's always something to keep you busy in maintaining and renovating an older house, but in doing that keeps them unique and a great place to live in.

 

It sounds like you have done great prep work already in relaying the bricks in order for the concrete to be put in. Considering you have a small area, it's not load bearing, and you are going to work on getting the bricks in/getting the corner cleaned out of loose concrete, I am with you with pouring concrete down there. The only time you would need to use a self-leveling flooring compound is if the concrete pad there is irregular or uneven up to the bricks.

 

You can use self-leveling compounds for the whole project, but typically most of those will get you no thicker than 1" at a time with each application.

 

So bottom line, you can pour a 3-5 inch concrete over the bricks with a mixer PROVIDED you have no moisture issues or will ever underneath. Poured concrete isn't about saving money, its also about saving time on doing this.

 

If you didn't see any moisture or dampness from the bricks that are in place already, you can go ahead with pouring the concrete over the slab, however its better to use at minimum a vapor barrier (6 mil plastic sheeting) first  and/or sand to help out the new final slab. Putting that vapor barrier down first guarantees you won't have any moisture issues in the future so your new concrete will last for years to come.

 

As for having the weight of the furnace on there, you'll have a nice foundation of bricks under the concrete, you'll be fine with that; provided everything is level and smooth.

 

Hope this helps you out,

aboveaveragejoe

Posted 2011-03-21T12:40:43+0000  by Joseph_HD_ATL

thereactually is a slight moisture issue there. the cinder block wall had some seepage issues, but we regrouted and dry-loked the wall, and its been dry  ever since. the bricks on the floor won't seem to dry, however. how much sand do i need to pour down there in order for it to be a proper vapor barrier?

Posted 2011-03-22T02:47:02+0000  by icabear3

 

Greeting icabear3,

 

My name is George and i work for a Chicago area Home Depot.

 

Icebear, sand it’s not a vapor barrier, what aboveaveragejoe was trying to explain is that you need to use sand in addition to the vapor barrier.

 

Approved vapor barrier for concrete slabs it is 6mil plastic or thicker.

 

So in other words in order to minimizes moisture permeability from the ground under the slab you would need to lay a layer of compacted  sand or gravel ( to create "friendly" substrate for the vapor barrier and allow water drainage)  over the bricks, layer of 6mil  plastic over the sand  and finish with a minimum of  4" of poured concrete.

 

Now, building codes vary through the country and yours may require an additional layer of sand or gravel over the vapor barrier to reduce water content and friction in between concrete and vapor barrier.

So please reach out to your building department to confirm exact placement of vapor barrier.

 

 

I would like to suggest another solution.

 

Bricks that you have down right now where probably used to fill the void in between concrete slab and the dirt under.

This is really not a best practice and I would recommend continuing and removing all of the bricks.

Why?

Concrete slab needs to have a thick layer of compacted porous gravel base under the slab to allow any accumulated water to drain out and if present to redirect water towards drain tile.

Vapor barrier it’s added to minimize the moisture permeability form the gravel base and dirt under to the concrete slab resulting in a friendly substrate for most floor finishes.

 

In other words bricks that you have down right now are not allowing fast drainage resulting in higher moisture content.

I would recommend removing bricks and replacing with a 4" of compacted gravel.

 

Hope that helps and welcome to the community.

 

 

 

 

 

 

 

 

 

 

 

Posted 2011-03-22T14:36:58+0000  by George_HD_CHI

thanks for the info guys! also, do i need to worry about installing a drain? if so, how big and how many will i need? the slab i will be laying down is looking to be  about 10' x 20'...

Posted 2011-03-24T20:19:35+0000  by icabear3

So it looks like we are working on a bit bigger slab than we thought :smileyhappy:

 

Installing a drain is something that is important to plan out at this stage before the slab is set in. From everything you've told us from the brick and concrete removal, it sounds like you have access to dig and set drainage pipes down there. Unless you will be having more than the heater down there, a drain may not be needed, but at this point before you pour, now is as good as ever to put one in!

 

Depending on location, size, and need, I would recommend talking or contacting a licensed plumber so as they can not only give you exact specs on building your drain(s), they more importantly will give specific plumbing/building codes for your area. This stage is also important if you know of have access to your blueprints or basic schematics on the house so you can see exactly what would be the best area would be for your drain. 

 

After getting the information from your plumber, installation will and can vary on size and even local codes. You'll need at minimum drainage pipes, duct tape, and foam pipe wrap to make sure the drainage pipes are secured during and after the pour. Hhere are some general tips on putting a drain down there.

 

  • Install the drainage pipes when you rough in the install above the level of the slab, making sure at first youll have enough length when you start doing the final plumbing work after the pour is finished. This part is crucial because you may have to install the pipes by breaking through foundation walls or other substrates to get the drainage pipe out. This is the step where knowing where to dig and if it is safe to do is key.

 

  • Using foam pipe wrap, wrap the foam around the new drain pipe and overlap each layer (like a Mummy) until the wrap goes out beyond the level of the slab's surface. You can use duct tape  and attach a loose end of the foam pipe wrap to an area of the drain pipe that will be under the concrete slab, then secure the ends of the foam pipe wrap with duct tape to ensure stability

 

  • Now cover the outside/ under slab  part of the drain pipe you dug with soil or the sand/gravel we discussed earlier. If all goes to plan, the pipe wrap will be above and below the concrete slab in its entirety. Then youll be green lighted for your pour!

Again, depending on how your walls and house is set up, it can be done, but consult with a licensed professional/plumber to ensure that you can do-it-yourself, but in a timely and effective manner.

 

Let us know icabear3 if you have any further questions.

aboveaveragejoe

Posted 2011-03-25T14:37:18+0000  by Joseph_HD_ATL

the floor of the basement is about 5 feet below grade on this project. the exit pipe for the plumbing goes through the slab. can i link the slab drain to the drainage line ?

Posted 2011-03-25T22:46:45+0000  by icabear3

I did an informal round table discussion with my building and plumbing experts here on the community, SteelToes and ChrisFixit, and we all agreed that it would NOT be a good idea to link the slab drain to the drainage line, if it is a sewage line for several reasons:

 

 

  • Separating the lines is a must, and its more than just being code, its just good practice
  • Drainage lines are only used to flow the ground water to the pit, and sewer/waste lines needs to be separated and redirected to a city line or septic tank
  • If you connected the lines together you would have waste pumping out into the yard where the tank or storage is located, since any water can easily overflow in there
  • If the sewage line got clogged or full, you'd have that coming up into your basement as well
Also icabear3, the location of the pump is key as well, so let us know where you'd be placing that and we can get a solution hammered out for you.
Thanks and keep us posted.
aboveaveragejoe

 

Posted 2011-03-28T14:14:40+0000  by Joseph_HD_ATL

Hey guys, just a quick fyi:

 

i called up my building an zoning, they came out an inspected. they let me know a drain isn't neccesary, and gave me a green light to get this done :) i got the filler bricks all pushed down an extra inch, and i have just started throwing down general purpose gravel down.  after that, i have some black 6mil sheeting i will be laying down, followed by the slab laying. the measured space of where the slab will be is 8 x 22. do you guys think it would be easier or more cost effective to hire a mixer truck, or just mix it in small batches in a wheelbarrow?

Posted 2011-04-15T16:04:27+0000  by icabear3

 


icabear3 wrote:

Hey guys, just a quick fyi:

 

i called up my building an zoning, they came out an inspected. they let me know a drain isn't neccesary, and gave me a green light to get this done :) i got the filler bricks all pushed down an extra inch, and i have just started throwing down general purpose gravel down.  after that, i have some black 6mil sheeting i will be laying down, followed by the slab laying. the measured space of where the slab will be is 8 x 22. do you guys think it would be easier or more cost effective to hire a mixer truck, or just mix it in small batches in a wheelbarrow?


 

That's awesome:smileywink:

Well for the 8'x22' slab 4" inches thick you would need around 99 bags of 80 pound concrete mix:smileysurprised:

That is more than two pallets and I would definitely consider getting a mixer truck.

Just be prepared for it when it comes... :smileyvery-happy:

I would recommend and I’ve use to build a ramp-funnel out of plywood on one of the basement windows which would direct concrete straight in to the wheelbarrow.

 

 


 


Posted 2011-04-18T15:58:21+0000  by George_HD_CHI

Hey icabear3,

 

Hopefully you got that mixer as SteelToes has suggested.:smileyvery-happy:

 

Let us know here on the Community how your basement floor is coming along! You've already done some great research and planning, hopefully the execution of the project will be just as great too.

 

If possible, could you send us pictures or even an update on your basement? Glad that we could be of help to you, and anything else you need, don't hesitate to let us know.

 

Have a great day!

aboveaveragejoe

Posted 2011-04-29T16:22:47+0000  by Joseph_HD_ATL
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