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Snow melting and concrete pavers

kiddoc's picture

Can anyone give me an idea of the layers required for embedding PEX tubing in a driveway using concrete pavers?  Without the PEX, I would need a 12 inch base of gravel, then a 1 inch layer of bedding sand.  I would assume that the PEX would go into the sand layer, but where would the foam insulation go, between the sand or below the gravel base?  How thick should the foam be, and wouldn't it crush under the weight of cars, leading to an uneven paver surface? 


Thanks in advance for any advice!

(post #110278, reply #1 of 6)

Don't do it (use pavers that is). While they are great for DIYers or anyone with a fear of concrete that WILL set up in a hour or two, you don't want them for a radiants snowmelt sidewalk, IMO.

I kicked it around for my own house because I had a bunch of utilities to run through the area in the next few years. And I couldn't come up with a design that would work so easily as tubing in a slab. Why?

The sand will be a much poorer heat conductor than a concrete slab. Therefore, the pavers will take longer to get to temperature and you'll use more BTUs to get there.

Unless the insulation is right under the sand, pavers plus sand plus gravel will have more mass than a slab right on insulation. Hence more time, more BTUs.

Paver-to-paver heat conduction will also not be great (sand fills the gap). So the ability of the sidewalk to transmit heat laterally is not as good. So maybe you need 4 tubes in a 36" width instead of 2. More installation cost, more pumping costs. Less uniform temps. So you have to heat it longer and hotter until the worst-case area has melted all the snow. More time, more BTUs.

With a slab, you can give it a good crown to shed water to the side. With pavers, water will percolate between paversdown into the sand, then gravel to some point where the ground is frozen. Then it will freeze under the pavers with different amounts in different places. Each paver, frost-heaved to varying heights.

So I just waited until all the subsurface work was done and put in a really slab with tubing in it. If you like the paver look, lots of outfits can dye the concrete and roller in a paver pattern.

It IS cool to look out at the new snow and flip a switch to deal with it! Although in practice, I usually quickly shovel most off and then flip the switch to get the last bits and leave it completely clean and dry. For a foot of new snow on a 3' x 100' sidewalk, it's about $5.00 of natural gas. If you shovel most of it first, then it is $1.00 to $2.00 depending on outside temperatures. So less than the neighbor kid charges and a much better job.

I think the biggest place to do it isn't uper-end homes but old-folks homes and hospitals, where rickety people are toddling about trying desperately not to break a hip.

You could do it with pavers. Throw enough BTU at anything and it will get hot. But I think you would be happier with a monolithic slab.


David Thomas   Overlooking Cook Inlet in Kenai, Alaska

David Thomas   Overlooking Cook Inlet in Kenai, Alaska

(post #110278, reply #2 of 6)

Thanks for the reply.

(post #110278, reply #3 of 6)

Don't be afraid of the concept.  Although I usually agree with David on most topics, I sure don't on this one.


I have installed about 20,000 sq. ft. of pavers over radiant tubing at a local ski area.  Compacted gravel set with pitch away from the building, 2" Dow foam, tubing clipped to foam, burried in sand, then the pavers.  Works great, ski area loves it.


Water does not typically seep through a completed installation.  If you have a low spot, you will have a puddle.  If enough pitch is established, water runs off.  I like at least 1/8" per foot, a little more is better.


've also seen thin foil-faced bubble stuff used instead of the foam. 


Bear

Bear

(post #110278, reply #4 of 6)

I'm on the verge of doing the same thing at my house. Paved area(driveway) is to be about 15'x45'. It already has a fairly steep grade of QP(about 8"-12" depending on area). I was thinkin that all I'd need to do is level&compact the QP, layout PEX, add 1" of sand, compact and lay pavers....


If I don't use foam ins, I don't have to excavate as the finished grade will be where it should(3" higher than it is now). I think I'll look into the foil, do you think it's worth it?


Mike

We do Fast, Cheap, and Reliable work.

Just pick any two.

Snow Melting Pavers (post #110278, reply #5 of 6)

We design paver snow melting systems all the time. It is true that they cost a bit more to operate than a monolithic slab, but they generally afford better drainage for snow and rain. 

 

Check your specs for pavers. 

 

 http://www.interlockpavingsystems.com/sites/default/files/Tech%2012.pdf

do do dahhhhh......... 13 (post #110278, reply #6 of 6)

do do dahhhhh.........

13 year old thread dude...