Replies

1. 
   calvin | Feb 23, 2011 07:28pm | #1

   In Earthquake country there must be flatwork rules or guidelines

   to reinforce the slab so it floats and takes the dwelling for a ride as one..................

   I would think.

   Not being from there I cannot say.

   As far as concrete hard to stand on, what floor covering are you going to use if any over that slab?  We have our heat in the floor in the whole downstairs living area.  All covered in ceramic tile.  We sit down.

   Cork is cushioning and I would think available to perform on concrete.  Check the spec's.

   As far as the pipes-back to the slab question.  If the slab doesn't crack, hard pipe would be fine-but now Pex and other flexible material is used for in floor slab heat runs. 

   We tied all our hose to 6x6 wire grid-I would think if rebar was spec'd for your reinforced concrete-you'd cross that for strength and could tie the hose off to that.  You don't just throw the hose in the wet concrete-it's run according to heat needs and is tied off to stay in place.

   David Meiland (regular here) builds up in that area-maybe he'll see your post.

   Best of luck.

2. 
   davidmeiland | Feb 23, 2011 08:57pm | #2

   If we have a quake

   that's big enough to break your floor slab, your house will be severely damaged and the tubing will be the last of your worries. Slabs break over time because of poor construction and/or site conditions that lead to undermining.

   Important points are to place and compact a very nice subgrade. Don't just throw some gravel down and drive the tractor over it for a few minutes.

   Put at least 2" of XPS foam under the slab with thermal breaks at all edges. 4" of foam is better.

   Use rebar, not wire mesh. Place the rebar mat on 1" or 1-1/2" dobies and tie the tubing to the top of the mat. Make sure none of the tubes are going to float during the pour.

   Use fiber mesh in the mix. Use a low water mix. Use a 6-sack mix. 

   Consider using an air/water heat pump rather than a boiler. This is a good climate for them and long term fuel cost will be much lower.

3. 
   DanH | Feb 23, 2011 10:05pm | #3

   It used to be common practice to bring the ends of the heating pipe runs up above the slab every few feet, to be able to patch around leaky segments.  Not done anymore now that most everything is PEX, I gather.

4. 
   Clewless1 | Feb 26, 2011 08:43am | #4

   If reinforced right ... generally I think that there wouldn't be issues. Talk w/ some other locals about doing this (e.g. heating contractors that have installed it). Get their take on it.

   Individual breaks may not be the end of the world. It is possible to repair a break in your tubing. I actually planned on it when doing my own house in Hood River. I just kept in mind the worst case where something happened (e.g. drilling a bottom plate anchor through a pipe). While definately a bit of a PITA, a repair can be done. My guess is that there will be other damage that is more significant if a slab breaks up ... the walls and roof end up w/ a lot more seismic force applied to them (they are up high and lateral shifting puts huge forces on objects that are tall). Barring a major rolling type quake (which is somewhat unusual, I think), the slab would survive more than the walls/roof ... assuming it was reasonably isolated from the foundation walls.