Self installed concrete floor?

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Extremebison

New Member
Dec 27, 2010
58
Yukon Canada
Been reading all over the net and this forum but can't really find my answer, so here's my ? Is it possible to pour concrete by hand for in floor heating? I only have about 500sq foot room to do. I live way out of town. I want concrete for the thermal mass and the fact it works at lower temps.

What kind of concrete?
What is the mixture ratio?
What size of pex to run?


I'm planning to go with 1.5" of concrete as this would mean I only have to lift two doors 3/4 of a inch.
 
What size of pex to run?

You will need to generate a heat loss calculation to determine pex size and layout. Definite foam board under slab, the thicker the better as well as the perimeter. Do not skimp on the insulation as the floor heat will be an exercise in futility. Search some past threads concerning this.
Is this an over pour or starting from scratch?

Tubing doesn't like being deep in the slab so keep that in mind. There are anchors for it to attach to foam.
PSI of concrete is determined by the loading of the floor.
Keep in mind the slab might need to be saw cut to contain cracking. If you can orient loops to aid in that endeavor you will be ahead of the game.

Will
 
Are you going to try and finish the concrete or just brush it and tile over it? Hand mixing 2 and a half yards and trying to finish it would be tough unless you had some help. An inch and a half isn't going to leave you much room for error.

Have you considered a cast iron radiator?
 
The answer to your question is absolutely, although if you mean by hand mixing your own it will take a little bit of effort.

I did two infloor pours. One in my basement with a 4" slab using 300' runs of 1/2" pex insulated with 2" foam board. Another as a subfloor on my mainfloor of 1 1/2" of lightweight pumice mix over tji joists. I feel like they both turned out good.
For the main floor : EVERYONE was telling me I had to do gypcrete, "Its the only way to go and it is how all the contractors do it." But gypcrete is expensive and I usually try to look at the problem with all solutions in mind prior to making a decision. I found a semi-local concrete outfit that said they could mix a lightweight mix out of pumice. I can't remember what exactly the mix was but I think it was similar to standard slab, probably 3/4" minus pumice with a 6 sack mix. If you are not worried about the load of the slab on joists I wouldn't even worry about the weight. For a 1 1/2" slab of "normal" concrete your adding about 20 lb/sf to your floor load. I put 6 mil plastic down against my plywood subfloor as protection against rot/moisture. I then ran 2x2s as fir-ing strips 2' on center. I then ran 1/2" pex stapled to the subfloor in between the fir-ing strips in 300' runs. Next we wheelbarrowed the concrete around screeting off of the fir-ing strips. I didn't put much of a finish on it because it was planned as subfloor. I gave the floor a good month or two to cure then put recycled maple flooring nailed to the fir-ing strips.

Good luck.
 
FYI- I believe The Radiant Design Institute is Fred Seton's work. He has been at it a long time. Good info...
 
Ya done a few dozen myself and we always put everything in the bottom for all the reasons mentioned in the links, No problems here either. Just another FYI point - contractors and customers don't under standtension and compression loading and if they did, concrete would never be poured with out some type of reinforcement. On larger floor projects we use #4 bar tied on 24 inch centers, this eliminates any possible shearing action caused by a moving floor.
 
Hi Extreem
I'v got a big mixer on wheels if you decide to mix your own.It works best with min 5 people if you want to mix a big batch.It will mix 5 big wheelbarrow loads at once,about 1/3 yrd to a mix.The more bodies you have the better
Thomas
 
Think long and hard about your floor loading first. It will probably need to be reinforced because you are adding 10,000 pounds of weight to that 500 sq ft. once you get a handle on that you can decide to proceed or not.

There are "recipes" out there for light weight concrete, otherwise known as lightcrete. Do some searching on the www. You'll also want to consider the fact that unless your subfloor is rock solid you will get cracking in the cement as the house and floor move seasonally. I don't know what to recommend for reinforcement as I have never done one like that. My brother in law used a 1-1/2" lightcrete over a wood subfloor in his house and it has a few cracks in it. The carpenter handled the pour on his job rather than a regular cement contractor so I don't know if it was done right or not.

Tube spacing, length of each loop and number of loops will depend on your heat loss for the room and the finished floor covering. There can be a significant difference in output and surface temperature depending on what you put over top of the pour.

Lot's of preliminary work to do before deciding to pour it or not.
 
sparke said:
FYI- I believe The Radiant Design Institute is Fred Seton's work. He has been at it a long time. Good info...

Nothing against Fred, who has done a lot for the wood burning industry, but some of his ideas on infloor tubing and slab heating are a bit outside the realm of normally accepted practices throughout the industry.

Good solid info here. http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=438
 
Heat loss calculations, I've been struggling with this one, as I live in a log house and burn 5 to 10 cord of wood in a winter. I don't have a bill to show Btu consumption.

This project is going to be a renovation. Not in a new house.

The current floor is well insulated under the plywood, all I think I need to do is rip up the old pine 3/4 slats. Insulate the perimeter, and lay my pex on the plywood. Lay some reinforcement steel, mix concrete and pour over the floor. I do realize it's not quite this simple.

Base board heating is always an option, but they require high water temps vrs in floor to heat. Plus the heat sink in the concrete will help times between firings of my boiler.

My plan is to get all my heat systems in place and work my way back to the boiler. Then building my boiler and storage last, as this will be the major investment.

We do plan on living at this house for a very long time if not the rest of out life, so doing the floor will be worth it.

Thanks Thomas for the offer may take you up on it. I got 20 cord delivered to the yard the boys gave me a good deal. I won't be heading your way to cut wood as I originally planned. I still want to get a tour of your place, just need to swing it, I often come spring bear hunting your way may stop in then. Or if I get bored and the-40 goes away for a day I may come over for a drive and a coffee.
 
Some interesting info here (link below). The dry clean sand option seems especially interesting- none of the mix/ mess of concrete, no worry about cracking, and plenty of thermal mass. You'd still need to be sure that the existing floor framing is "up to" a substantial increase in dead load of the floor.

http://www.radiantcompany.com/details/suspended.shtml
 
heaterman said:
sparke said:
FYI- I believe The Radiant Design Institute is Fred Seton's work. He has been at it a long time. Good info...

Nothing against Fred, who has done a lot for the wood burning industry, but some of his ideas on infloor tubing and slab heating are a bit outside the realm of normally accepted practices throughout the industry.

Good solid info here. http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=438

As far as laying the tubing ,tubing spacing , depth of tubing , insulation and such. Everything that Seton has described on his web site worked great for me.

Huff
 
pybyr said:
Some interesting info here (link below). The dry clean sand option seems especially interesting- none of the mix/ mess of concrete, no worry about cracking, and plenty of thermal mass. You'd still need to be sure that the existing floor framing is "up to" a substantial increase in dead load of the floor.

http://www.radiantcompany.com/details/suspended.shtml

I like the idea of the sand also, especially if your putting OSB over it. I'll have to research that idea more as it would be allot easier than mixing concrete, or tearing out the basement finished ceiling to install flat plates.
 
The weight of the concrete/gypcrete/litecrete is the biggest problem to overcome. 500 sq ft X 1 1/2" = 2.31 or approx 2 1/2 yds of concrete, at approx 75# per cubic ft or about 5000 pds for pumicrete. A regular concrete/grout mix would weigh about double this.
If the floor can handle it the rest is easy.

Contractors use gypcrete because it was designed for this very application, lightweight, easy to pour,(can be mixed very thin without unreasonable shrinkage making it very easy to level) but it is pricey.
If you can come up with a lightweight concrete grout mix such as pumice you dont need steel (#4 rebar) all you need is fiber.
In an 1 1/2 floor #4 rebar wouldnt do much good (1/2" rebar + 5/8" OD pex would only leave 3/8" of concrete out of an 1 1/2") and would just add weight to a floor that is already overloaded. the fiber wouldn't add any significant weight and is a lot easier to use.
You can get it at any concrete company.
If you could determine the floor could take the weight I would not hesitate to try it.

One thing to keep in mind is if the floor is in an older house like mine it might have undersized floor joists (2X8 when they should be 2X10) making them kinda bouncy. Without extra support there wouldn't be any reinforcing material that would prevent the concrete from cracking and breaking, but is easily fixed if you can access the bottom side of the floor joists and can add support. Of course this is assuming you are talking about pouring over a wood floor.
 
FWIW: I have to agree with the cautions above about the total load you will be adding to a wood floor of ?????? type of construction.

If you want to provide detailed info on the floor const, for example 2x10@16" O.C. clear span distance 12' with 3/4" plywood glued & screwed at 6" O.C. Or whatever your situation is then we may be able to give you an idea of the total load (all live & dead loads combined) that your floor can safely support.

BTW fast seat of the pants calc says the weight you intend to add (1.5" of concrete) is about 50% of the total load that a typical wood floor is designed to bear. So you would be pushing the limits to say the least (once you add all the other loads).

FWIW I would never do this on a typical wood floor, there are just too many other low weight options out there that are going to yeild the same results in terms of "comfort" which I assume is what you want.

Also keep in mind that if the worst were to happen & the floor failed structurally due to this excess load your ins co would walk as I doubt you will have an engineered drawing & stamp approving the additional loads.

IMO look hard at the low weight high comfort options others have provided to you in their posts.

Dont take a flyer on the structural integrity of your home, nothing worse than having the living quarters moved to the basement via gravity & no ins to cover the loss=bulldozer time.

Hope this helps.
 
The sand method looks like a real good way, eliminating the concrete = all together, and all the problems that can come with it. There's some nice sand dunes just down the road I can make use of. I'll research this method some more.
 
Pouring 2 inches is tuff, have done this also, and it will never be crack free. Over existing wood framed floor, we have ripped 3/4 plywood in to 12 inch strips and laid them out with just the gap of the tube 5/8. then stuck in the thin alum. heat plates and covered the whole thing with cement board, then ceramic tile. This works well and even works better if the under side can be insulated. The over pour is way over simplified, IT"S VERY VERY HARD to get a good floor, one big room is easier but a whole house with closets etc, not so much! If you do pour it make sure the you incorporate a plasticizer.
 
As far as how the floor is built of I'll have to tear up the thing and just see. The house was built in 2000. But this is the Yukon you never know what one will find. It is the ground level floor, I can't get under it to see as the logs go right to the foundation. One would think it's built to code, but I already have problems with the septic, and I ask who approved it and I get sent in circles and told I'm on my own. Also I replaced the outside lights with motion lights and found the connections were made with vapor barrier tape, so much for a electrical inspection. So who knows how the floor is built.

Thanks for all your help
 
Heres a bunch of pics. of my install and pour for my house. It was a 1-1/2" over 2x12 joists 16" OC. no spans mor than 12' with an Engineers stamp and approval.

Huff


sorry I cant get the link to work

http://cid-105ddae62e67650d.skydrive.live.com/redir.aspx?page=play&resid=105DDAE62E67650D!192
 
Is it that important to have that thermal mass to store and even out the heat? I added a little mud room on my home last year and installed in-floor radiant. I laid down 3/4 inch polyiso sheets then added seven inch strips of good birch plywood spaced to accept 1/2 inch pex and layed the tubing in the slots. I then put down 1/4 inch cement board in thinset and nailed it (carefully between the tubing). My first design was to lay aluminum plates over the tubing to help distribute the heat but then decided to leave out the plates and just trowel the thinset right into the tubing. , I then laid porcelain tile on top of the cement board. Second heating season. No cracks, no squeaks yet

The rest of my house has staple up radiant and heats fine but the only time the floors are warm enough to make me giggle is when it is below zero and the house is calling for more heat. The new mudroom floor cycles more often but is very warm to the touch which makes it a pleasure to remove my shoes and boots and stand on it. I can't feel the changes in temperature when sliding my hand from one tube location to another but being a real tenderfoot, I can feel it with my bare feet.
 
my mud room is from the 40's, it was laid up in block and the floor poured to edge of the block, walls built on that. the whole thing sticks out of the ground 3 courses of block and is exposed on there sides. Water would freeze out there over night if the door to the house was left closed. 10 years ago I poured 2 inches of concrete over the concrete slab with tubes embedded and tiled over that. There is 1 run of 1/2 tube for the whole room 12x 12. This is the worst case from an insulation and exposure standpoint, for in floor. This room heats great can't be putting in more then a couple gallons a minute of warm water. It has mass!!
 
bigburner said:
my mud room is from the 40's, it was laid up in block and the floor poured to edge of the block, walls built on that. the whole thing sticks out of the ground 3 courses of block and is exposed on there sides. Water would freeze out there over night if the door to the house was left closed. 10 years ago I poured 2 inches of concrete over the concrete slab with tubes embedded and tiled over that. There is 1 run of 1/2 tube for the whole room 12x 12. This is the worst case from an insulation and exposure standpoint, for in floor. This room heats great can't be putting in more then a couple gallons a minute of warm water. It has mass!!

So are you saying the mass helps with the heating? I would think that if the heat that is put through the tubing is used and not wasted through loss the only difference would be cycling time and response. My floor is over a basement built of iSPs but there is no heat down there. The temperature runs about 47 degrees. I'm sure most of the heat comes from the 12 foot concrete basement wall on one side. I have 8 inch batts of fiberglass insulation in the joists. I think I'm running my water too hot, hence the frequent cycling but I need the hotter water for the staple-up since there has been so much rework done to the house the floors are 2 1/4 inches thick and I'm too cheap to install another mixing valve.
 
I'm seeing some things and suggestions here that are making me nervous..........


Here's another option that works extremely well. In fact my bare feet are resting on it right now as I sit in my chair. No weight or structural concerns, only adds 1/2" in height to the floor, very even heat, water temp requirements are nearly as low as gyp or concrete. Response time to heat input is about as good as you can get with a radiant floor. Off the cuff I'd say it's probably 4-5 times as quick as a thin pour.

here's a blurb http://www.ebuild.com/articles/1211498.hwx

here's the whole 12 minute video http://www.viega.net/productcatalog.html#model-group284639617504

We have put down literally tens of thousands of sq ft of this product. It works and works well.
 
Extremebison said:
The sand method looks like a real good way, eliminating the concrete = all together, and all the problems that can come with it. There's some nice sand dunes just down the road I can make use of. I'll research this method some more.

Sand is a better medium for insulating than conducting. They make firebrick out of the stuff........??? just sayin.........
 
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