Concrete floors?

[iceman]

With pics??!??

Flattered, but no.

[Rossymcg]

A TR's not a TR with out pics,
Under floor heating all the way, you'll never regret it, I've worked on projects where we've installed it upstairs as well,
Fitted ridged insulation between the floor joists 2" lower than the top of the joist, ran plastic pipes on top of the insulation, then filled inbetween the joist with screed, then chipboard flooring sheets over that, costs more than normal central heating but by far superior,

[jamesp]

why not thin (2-3"?) concrete floors upstairs also?
Too heavy, or joists not big enough in an existing house?
Or is it just cheaper to do as you suggested?
Or did owner not want concrete floor upstairs, & method you suggested allowed for wood or other floor covering? On that note, I thought wood floors & in-floor heating was a no-no? Is expansion & contraction worse with in-floor heat?
BTW what is "screed"?

[Rossymcg]

Screed is sort of concrete with out the pebbles in it, it has fibres in it to prevent cracking,it comes drier than coni as well more like a damp sand consistency, chipboard flooring more stable than normal wood as it has a high resin concentration,
I've also done the underfloor heating with metal plates fitted on the joists spanning from joist to joist, with the plastic pipes going through channels under the plates, the pipes heat up the plates and transfer it through the chipboard or plywood floor,

If we'd have raised the floor on the upper floor by 3" with a thin layer of screed, top tread would have been 3"" higher on stair, would have had to change doors leading out on to balcony etc,

[jamesp]

ok cheers. So if you were building a new place then there would be no reason not to put concrete floors upstairs? Or put concrete with wood on top if so desired?

[OSECS]

Cost effective
cool acid wash finishes
is most 100% definitely hard on the back after a while.
Radiant is nice. Takes a while to warm up and cool down, so the system should be one that has this factor built in. You can go hydro (definitely) pricey or electric (less pricey) radiant slab systems
Yep to the dust issue, typical of any slick floor with nothing to grab the dust.

Concrete is a fluid building material, find ways to exploit that characteristic in the design. Piece of furniture (bench) that is poured monolithically with the floor, continuous steps, curvilinear forms, bath tubs/shower pans .....

[iceman]

@james: Yeah you can do whatever, you can put concrete over wood no problem as long as you build it right and there's nothing too difficult about it. I've been focused more on the first floor because of the whole slab/frame construction thing. The concrete doesn't need to be on a slab but from a thermal mass/energy use standpoint it's kinda cool if it is. Likewise you could put wood flooring over a slab, and while that can work fine there's no particular benefit here if costs are comparable.

[Rossymcg]

ok cheers. So if you were building a new place then there would be no reason not to put concrete floors upstairs? Or put concrete with wood on top if so desired?

If I were building a new place, I'd use block and beam construction floor with with the under floor heating in mind,
We build different in the UK to you lot out in the States, I've never been on a project where the, Structual engineer or the arci have spec'd concrete to be laid on a timber sub floor,

[brice618]

ok cheers. So if you were building a new place then there would be no reason not to put concrete floors upstairs? Or put concrete with wood on top if so desired?

Depends a lot on what local concrete subs know. Likely the guys who do residential projects haven't done much other than on grade placements. So you'd have to find a commercial guy (both framing and concrete) willing to take on a smaller project which would cost more.

[AlpiNord]

why not thin (2-3"?) concrete floors upstairs also?
Too heavy, or joists not big enough in an existing house?
Or is it just cheaper to do as you suggested?
Or did owner not want concrete floor upstairs, & method you suggested allowed for wood or other floor covering? On that note, I thought wood floors & in-floor heating was a no-no? Is expansion & contraction worse with in-floor heat?
BTW what is "screed"?

A typical thin slab is 1 1/2" because an additional 2x plate is added to the framed wall heights. It is very common here and gypcrete used to be the material of choice, but at last check, lightweight concrete seemed more common. Reasons to omit it on various floors or areas is cost. The framing needs to accommodate whatever the dead and live loads are so it is a structural design consideration. Retro-fitting may require beefing up existing structural components, including footings (and trimming door bottoms and a slew of other adjustments).

Another consideration is to basically figure concrete cracks and can transfer the crack through directly applied tile. Control joints help, but doesn't guarantee there won't be stress cracks in other areas and aren't typical with thin slabs, so a slip joint might be worth considering for tiles, especially softer, weaker Mexican tiles.

On upper levels, baseboards or staple-up/under floor with R-11 and higher reflective insulation underneath is a more cost effective method than thin or thick slab. It's more conventional and the quicker temperature swings might be more desirable in sleeping areas. You can still have thin slabs in bath areas, but would either need to step down framing or step up.

My place has a sweet 6" radiant slab dining/sunroom with roof shading control, underfloor mostly and baseboard. Also, a fan coil from our solar system in my 'bat cave' office which blasts heat for instant gratification. I really wish I had added the radiant system to the office slab on grade, especially this time of year. Conversely, it's the most comfortable place during hot summer days due to the mass and orientation. With the boiler in the garage, the ambient heat keeps the vehicles and shop area comfortable.

[Buster Highmen]

We put them in the basement of our place integrated into the slab. We were warned about about the radiant that goes into the gypsum layer on to of anything as likely to cause it to break down, particularly on any flooring that might flex. Tile and area rugs work. That system is integrated with a radiator system throughout the upper floors which works well with zone controls.
The caveat for the radiant floor is the amount of time thermostat adjustments take to have an actual temperature effect. The zones heated by the radiators don't lag in that regard.

[AlpiNord]

An additional tidbit is that as mentioned, a radiant slab's efficiency is relative to basically keeping it cruising at one temperature. In larger volume spaces and open plans, the fact that the heat is where you are and is radiant versus convective (forced air), you are more comfortable at lower temperatures for the space. Often, you simply can't get enough hydronic baseboards in open, high volume spaces. A radiant slab or forced air system will be better than baseboard heat. Additionally, the radiant floor conductively heats up furniture as a bonus.

With convective heating, you may get the air stratification with the heat tending towards the top. Ceiling fans are nice no matter what system, but the whole volume needs to be warmer with a convective system for you to feel the same comfort level. FWIW, baseboards are a combination of radiant and convective heat.

For the bomb, run tubes in concrete counter tops, tubs and showers (including the walls).

[plugboots]

We have radiant in the upstairs also under the carpeting, and we would not have put it upstairs if I had to do it over. We get so much heat from downstairs, that we never turn it on. Partly it's the design as the upstairs is like a loft. The ceiling fan helps, but it's plenty warm, and we like it cool to sleep.

[jamesp]

For the bomb, run tubes in concrete counter tops, tubs and showers (including the walls).

Now there's an idea. Thanks for the info... useful for my day dreaming

When/if I ever get to build a place I'd love concrete floors with radiant heating. I don't mind the look of stained/polished concrete. I assume tubes in the concrete slab with a boiler, maybe take advantage of the sun (big windows) etc if the aspect works.
Keep the temps pretty cool but have a wood stove to provide extra heat for the living areas on cold days. The radiant heat could stay the same cool temp during the day, so as not to waste heat by having it cranked during the day when no-one is home, the put a fire on for extra warmth in the living areas in the evening.
Living areas upstairs (or same level) so as to keep bedrooms cooler. Having a concrete bath tub or shower with radiant heat in the walls would be super funky.
So it sounds feasible to have radiators in some areas if you wanted extra heat available, all connected to the same tubes / boiler as the radiant slab?

[AlpiNord]

Now there's an idea. Thanks for the info... useful for my day dreaming

When/if I ever get to build a place I'd love concrete floors with radiant heating. I don't mind the look of stained/polished concrete. I assume tubes in the concrete slab with a boiler, maybe take advantage of the sun (big windows) etc if the aspect works.
Keep the temps pretty cool but have a wood stove to provide extra heat for the living areas on cold days. The radiant heat could stay the same cool temp during the day, so as not to waste heat by having it cranked during the day when no-one is home, the put a fire on for extra warmth in the living areas in the evening.
Living areas upstairs (or same level) so as to keep bedrooms cooler. Having a concrete bath tub or shower with radiant heat in the walls would be super funky.
So it sounds feasible to have radiators in some areas if you wanted extra heat available, all connected to the same tubes / boiler as the radiant slab?

Slabs typically run at lower temperatures than baseboards, radiators, underfloor and fancoils. The more temperature variables you add to the control and manifold system, the more tempering valves and other factors increase costs, but doable. Just don't go nuts if it's about money. So does integrating LP/gas or electric heat sources with active solar and geothermal (heat pumps), for that matter. We found simply adding electric heaters in the bath areas the most cost effective......but if you had a concrete tub and shower mass with hydronic tubing on a zone, it'd be damn near blissful.

[jamesp]

the town I live in has no natural gas mains, but propane tanks are available. Most houses seem to have a combination of wood heat & electric baseboard. Baseboards must cost a fortune in shitty old poorly insulated houses. Luckily I rent & don't pay the heat bills. I've heard propane is nearly the same price as electric & wood pellet furnaces are the cheapest to run if you don't want to deal with collecting/chopping firewood.

Having options would be nice. Maybe a pellet/propane boiler heating the slab, the wood stove for extra heat like I said. Propane provides the back-up if you were away for a while &/or the pellets ran out? I'd also want a gas cooktop so propane has to be in the mix somewhere.

Geothermal heat pumps sound good but I think they are crazy expensive ie $20k!

[AlpiNord]

Some have added a heat exchanger and circulating pump (or rely on thermo-siphoning) to their wood stoves to move heat to other parts of a house. Multi-fuel boilers might be worth a look and a simple loop from a couple active solar panels can heat a slab when their's sun.

[jamesp]

You mean a heat exchange on a wood stove to heat the fluid circulating in the hydronic tubing?

Unfortunately insurance companies don't like that in BC. Any sort of wood fired boiler won't be insured by anyone unless its min 50ft from the house (ie in a shed out the back). Its kinda dumb, pellet or gas fired boilers are all fine & dandy, but not wood fired.
Lady at the insurance broker says it doesn't make sense, but she figured it was un-common & most wood fired boilers are home made. She thought it would only change if commercial wood fired boilers became more common, but who knows how long that might take.

[AlpiNord]

Yeah, it's more of a DIY, off grid approach requiring regular maintenance and hand holding. A heat exchanger simply conducts heat from a heat source (stove, boiler, solar panel, etc) to water or glycol mix flowing through it.

[Pow4Brains]

For any radiant slab on grade ensure there is 2" of Dow Blue Board (or any R-10 ridgid insulation) placed on the ground prior to pouring the slab (this requirement is now part of the CO energy code). This prevents the heat from going down in to the ground costing you cash. Example - My neighbor and I both have ~1500 sqft on grade, his doesn't have insulation under the slab. My gas bill has never been over $200 and his is +$450 in mid winter.

[Pow4Brains]

The concrete doesn't need to be on a slab but from a thermal mass/energy use standpoint it's kinda cool if it is.

This. There is even a sizeable difference between the lightweight gypcrete commonly used on top of wood sub-floors vs a normal ~3000 PSI concrete slab . DO IT!

[plugboots]

Here's a picture if my friend's:

I like the look a lot.
He never turns it off, just down to 50 if they're gone.

[Buster Highmen]

Why no basement?
Consider putting one in with (well insulated) themal slab in the 3/4s that's not designated cool space (root|wine cellar).

The new concrete forms of styrofoam make killer insulation (they just leave 'em in).

It will heat the whole house.

[iceman]

Why no basement?

For one thing we don't really need the space, for another it's right on top of granite ledge so digging is problematic at best. The third thing is that it's in a historic district and we're restricted on the ridgeline. The lot slopes pretty significantly, you could do an "English Basement" type deal even with the ledge there but you'd end up pushing the ridge higher than we can go. It's one of those deals, if we decided to fight them on it we would probably win but it would be a expensive pain in the ass and the people on the Historic commission all live right around there and I'd just as soon stay on good terms with them.

[jamesp]

Here's a picture if my friend's:

I like the look a lot.
He never turns it off, just down to 50 if they're gone.

those floors look good. I gather a lot of the variation is from the acid wash/stain... but the whiter patches in the centre? Is that wear or just weird reflecting light?