masonry plate brooder for chicks?

I've been reading over old posts about keeping week old chicks alive, most recommendations are for heating pads.  We live off grid in a fairly cold climate and our house temperature is generally between 65 and 70.  We heat our home with a masonry heater, and I am thinking we could replicate a plate brooder by heating up a thick masonry tile and placing it over a stable frame so the chicks could snuggle under there when they want to warm up.  As a backup, we would put them on the bench portion of the masonry heater at night, so they'd have some warmth coming up through the floor as well.  

Has anyone tried something like this?  Or does anyone use a plate brooder?  Any idea the usual surface temp of the plate?    

We do chicks and ducklings with a ceramic tile on top of which is an inverted clay flower pot with a 12 volt DC 35 watt halogen light bulb wired into the drain hole (we're off grid). The flower pot is surrounded by some hardware cloth to keep chicks from getting into direct contact in case it's too hot. Above this contraption is an old lid from a pan hanging from a chain with a towel draped around/over it. The chicks cluster around the flower pot under the cover. The cover can be raised as the birds get bigger. They seem to like their artificial mama just fine. The tile is nicely warm but not hot to the touch. The light under the flower pot doesn't illuminate the area so additional lighting is needed for the daytime and we just put on a very dim night light so they get used to darkness and sleeping the night through. For ducks they will get up and eat and drink at all hours so some night time illumination is necessary. This method has worked well for all the small batches of poultry we've done, about 15 birds max. For more birds a second "mother" is probably a good idea.

Thanks for this response, Larisa!  We're on 12V as well... this is the most energy efficient idea I've come across yet!  I think I can picture what you're describing, but any way you would be able to post a photo?  I'm also curious what you use to enclose the masonry mama?  

Sorry I don't have any photos and the brooder supplies are all packed away as we didn't do any new birds this spring. We actually set up the masonry mama in an extra large dog crate that has a blanket over it so the whole area stays nice and warm. We have a daytime light in there so they can see. After the first few days we leave the door open into an adjacent cardboard box "corral" that we put a rubber mat in the bottom for clean up ease. They can go into this area and run around then dash back to the dog crate where the heater is and their food and water. The hardware cloth around the flower pot is just a cylinder and not sure if it's absolutely needed or not. The cloth over the pan lid (which is a domed cover from a wok pan) is just a rag and gets removed after the first couple of weeks. The first year we did this we were monitoring the temps constantly and changing out the wattage on bulbs until we got it right, then realized the chicks were the best indicators of how comfortable they are. Hope this helps without a photo, but feel free to ask more questions. I do like the commercial chick heaters but they are A/C powered and that means running the inverter 24/7 which is less efficient.

This helps a lot!  This is our first time brooding chicks so I'm nervous... But I can picture your set up in my head.  Thank you!