lightweight concrete

[par4thecourse]

I'm preparing to pour lightweight concrete over the radiant floor heat pex tubing. The local readymix companies don't like dealing with it and charge accordingly. To further complicate the lightweight concrete job I will try to add integral colors. The local readymix folks don't like color either. It's only about 4.5 yards so I decided to rent a mixer and give it a try.

The lightweight aggregate requires a good long soaking. Beyond that and adding the suggested amount of integral color I'm not sure what would make this different than any other concrete finish floor.

I must be overlooking something. Does anyone here have experience with this type of work that could offer any suggestions?

par4thecourse

 

[Henro]

I don't have any experience, but I will throw out a question: Why lightweight concrete?

The reason I ask is the first thought I had was that light weight would equate to low thermal conductivity. Since radiant heating wants heat to travel from the tubing to the surface of the concrete...could light weight concrete be undesirable? Or is it that less mass means quicker thermal change of the concrete and faster heating if you need/want to heat things quickly?

Could light weight = less durable?

Hopefully someone with experience can help you...I'm all questions and no answers... /forums/images/graemlins/blush.gif /forums/images/graemlins/blush.gif /forums/images/graemlins/blush.gif

 

[gollum]

Par

I will be doing the exact job here in another month or so. I have been researching as much as possible. What are you using as an aggregate and were are you getting it? There is a patented mix out on the market, but only franchise owners, who apply it are able to get from the manufacturer.
As far as color goes, the best jobs I've seen were done with colored powder sprinkled on before it sets up hard and then rubber mats with brick, stone, slate,ect. impression on them were tapped, with a mallet , and then allowed to harden. That's my plan anyway. Are you planning to give it a brick or stone look or just a smooth finish?

E-bay has those matts -- around $100 to 150.

Here is a sight that might give you some ideas --it's amazing what they can do with that stuff


Henro
The reason that you use light weight concrete is because it is poured on a first or second floor, and not on dirt (thought it can be in basement or garage). The floor joist are beefed up so the less weight in this case, the better. The light weight concrete has more than enough thermal mass to get the job done. Heck, they're even using aluminum plates under the flooring to transfer the heat and getting good results.

Gollum

 

[tc35dforme]

2 comments....plan for thermal expansion, and be ready for cracks, especially if there is and flex at ALL in the subfloor and structural system. If you plan on leaving the concrete exposed as a finished floor, you best make sure everything is 110 % perfect, or you'll get some ugly results in a few years.

I couldn't go with a concrete system since my timber framing ( post and beam ) is very dynamic and would result in a mass of cracks in a few years. I've got the aluminum reflectors over wood. Just the trade off for the tradional framing style.

 

[par4thecourse]

Gollum

I'm planning a smooth finish and really don't care if the color isn't uniform.

The aggregate I'm using is 3/4" pumice that a local ready mix company had a small pile of left over from another job. They said they soaked it overnight in a mixer and it was still difficult to work with. It tended to suck the water out of the concrete. I'll soak it for a few days then let the excess water drain off before adding it to the mixer. I can't find much information on a tried and true method.

tc35dforme

Thanks for the heads up. The concrete will be 1.5" thick (thin), 1/2"
pex tubing fastened to the deck. I will lay wire mesh reinforcing on top of the tubing. People have been telling me not to bother with reinforcing but I feel it should be done. I will also add temporary support to the widest span until the concrete has had a good long time to cure.

I will be glad to get this part done. I plan to have a weather tight shell up before it gets to cold.

par4thecourse

 

[tc35dforme]

Just another thought par4thecourse....

If you haven't already started with the tubing install, make sure you keep the tube on the warm side to ease installation. A nice sunny spot with a little plastic sheet greenhouse is nice to warm up the tubing. Keep the reel under there as you uncoil it and it will be much easier.

I did mine in the middle of the summer and ran each 600 ' coil down the front yard and fed it in through a window. Worked well ... no twisting problems. If you can't do this, make and uncoiler with a lazy susan thing. don't try to pull it off the roll. You'll regret that due to excessive twisting.

Get yourself a few repair couplings and be sure to keep at least 40 - 50 psi of air pressure in the tubing after you get it stapled and ready for cover. If ( I hope not !! ) something causes a hole, you'll here it immediately.

What are you using for controls ?? Check out Tekmar tekmar . I use a 360 control with a mixing valve. Works very well.

 

[par4thecourse]

tc35dforme

Wow! Uncoiling the tubing down the field sounds like a great way to do it. I put 390' of 7/8" pex in the basement slab (uncoiling as I fastened it to the reinforcing mesh). It was quite cumbersome. It was also a very hot day so bending was easy.

Other than deciding to use a propane water heater I haven't come to a desision on the rest of the heating system. Thanks for the Tekmar link.

par4thecourse

 

[Hoeman00]

When I put 2000' of 1/2" pex in the basement and garage floor.
I laid the 6x6 wire down first then started at the manifold and unrolled the coil (like rolling a tire) on top of the wire it went right around for 6" radius at ends.
The kids used nylon wire ties to anchor it to the wire.
A couple of hours and had it all done.
U probably already know but start your lines on the outside and work in.

 

[dmccarty]

Par4,

I don't have an answer to what you are doing but here is what
we plan on doing with our house.

We will have slab on grade so we don't have to worry with the
wieght issues. The color will be throughout the concrete. It
costs more to do it this way compared to throwing the color
on top of the slab and bullling it in. We are doing it this way
just so the color is all through the slab.

We are not having any impressions done on the slab. We want
it smoothed out. BUT, we are going to have them cut the slab
into a rectanguler shapes. Hopefully this will cause any cracks
to go where we want them to. As part of the house
design I have a grid pattern drawn for each room. It worked
out that each room has a grid roughly 3'x3'. Sometimes a little
more.

I assume you have researched the tubing. www.radiantec.com has lots of information on radiant
floor heating. Somewhere I picked up that a good design/price
point on active solar heating was to have 50% of the house
on active solar. We have a passive heating designed into part
of the house to help out plus the wood stove and lastly the
heat pump. Hopefully the heat pump will never be used.

Some states give out tax credits for putting in solar.
www.dsireusa.org has a map of the states so you can
see if you can get solar credits.

Hope this helps,
Dan McCarty

 

[TractorLuvr]

Ask around for a gypcrete contractor around your area. We in the apartment business use gypcrete on the 2nd and 3rd floors, strong like concrete but not as heavy