Old adobe home: Flooring/ heating/ insulating quandary
Hello, I am remodeling a 1930s adobe and considering flooring/heating/insulating options. Already determined is that there will be in-floor radiant with brick as finish floor.
What I can’t decide is whether the tubing should be in a new slab poured throughout the house (right now the “floor” is just dirt), or whether I can put the tubing in sand and have brick as finished floor. I think it would be nice to avoid filling the house with concrete and it would save on labor in terms of how much I have to dig down inside the house to get the right grade; however there are areas where I worry about settlement/compaction issues over time, for instance under the bathtub, and in high traffic areas or areas with heavy furniture on top.
I will compact beforehand, but face certain challenges. I can’t use a gas-powered compactor inside, and I need to be sparing with how I apply water to the ground, given that the house is made of adobe and the footing of rubble with mud mortar.
In either scenario I am trying to figure out how to insulate. This is climate zone 5. The building is all adobe with no insulation in the walls, and the footing is rubble, likewise uninsulated
One thought I had was to first insulate the footing on the inside by going down 24-in with 2-in rigid. Then I was thinking of installing radiant pex panels throughout the house, like the Amvic product sold at home depot (image below). In most areas I would add a sand bed to fill the grooves and cover the radiant, and lay brick on top of that. In areas that might be supporting heavy loads, like bathroom (where I also want to tile), I could pour concrete on top of the panels and then put down the finish floor. I was hoping another benefit of this would be increasing the response time of the system, as the climate in my area can fluctuate rapidly from day to day during certain seasons.
Any thoughts? Do I still need to worry about an uneven floor, with the panels bowing or cracking under the weight above wherever there are inconsistencies in the ground itself? And do I need to buy that insulation product or could I improvise a similar situation?
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Replies
User 69etc.,
First of all, can you tell us your name?
You are undertaking a remodeling project in an adobe house with a foundation described as a "mud mortar footing." Your house has a dirt floor.
Under these circumstances, I suggest that you hire a local architect or general contractor experienced with old adobe houses to guide you. I certainly don't have enough experience with the type of house you describe to provide useful advice.
It seems to me that there are a lot of opportunities for failure here. Good luck.
Rubble footings are pretty standard in old adobe homes.
We are down to dirt inside because that was what the now-removed floor joists were sitting on to support the old wooden floor. Also pretty standard...
My concerns are not structural -- an architect and contractor are already on board. They have differing ideas about insulation and flooring, which is the subject of my post. My own research has generated even more opinions. But your point is taken; I will seek further advice elsewhere than here
User 69etc.,
It's fine to seek advice here. I'm just stating my own limitations.
I'm familiar with rubble footings. A rubble footing sounds preferable to a "mud mortar footing."
I have no idea whether excavating on the interior so that you can install vertical rigid foam at the perimeter of a proposed new slab would have implications for the integrity of you home's footing. But if are are confident that such excavation is possible, then I would advise you to install the vertical rigid foam at the perimeter and proceed with a new slab.
If the slab is being heated, in a zone 5 location you'll want insulation under the slab too, not just slab-edge insulation.
Dry sand runs about R0.6/inch (even an inch of sand is twice the R value a 4" slab) so you DON'T want to bury the tubing in sand- put the tubing in a slab.
Amvic is basically R10 Type-II EPS (1.5lbs per cubic foot nominal density) molded to make routing the tubing easier. In high labor cost situations that might make sense, but even Type IX (2lbs density) is substantially cheaper than Amvic, and has sufficient denstity that plastic staples designed for radiant tubing can work. With Type VIII (1.25 lbs) or Type-II the staple approach isn't going to work, but tying the tubing to the reinforcing steel (whether rebar or mesh) does. Type VIII EPS is commonly used as roofing insulation under large membrane roofs in commercial insulation, and often available at VERY low cost from reclaimers. Reclaimers often have polyisocyanurate too, but that should NOT be used under slab due to it's moisture-retaining characteristics (if it ever gets wet it will take forever to dry under a slab.)