Slippery Slope; Snow Insulation

NYplumber

Whats the steepest angle to insulate (foam) below slab? Or is slope a non issue?







The job in question has a yet to be determined short steep driveway (angle unknown at this stage of the job). The rest of the walkway will be insulated, as will the horizontal area of the driveway leading to the slope.





Thanks in advance.

Gordy

The Pour

 To me insulate. The one who will suffer will be the guys pouring the concrete, or laying the asphalt if its that steep. The thing they would have to look at is room to get redi mix trucks along side the driveway out of the foam area ideal for you anyway no sense in having crushed foam, and tubing wrapped up in duals. I would talk HO in pouring concrete. Asphalt involves a paver on the work area, and trucks to load the paver also in the work area.



  The concrete guys will have to pour a low slump mix or it will be at the bottom of the hill. I have poured 4" slump on visquine at 10" thick the concrete runs like no tomorrow that was  pavement on a super elevation no uphill slope. A 4" slump is stiff to a lot of concrete guys. 



 The asphalt contractors issues will be the trucks, paver, on the foam. I imagine if the driveway is not to much tonnage they could load the hopper on the paver, and send that up the hill avoiding the truck traffic, but then depending on how big the drive is could be multiple trips over same area. The roller on the slope would be an issue regardless of the foam.





  One other thing that comes to mind is the stability of the slab wanting to creep down hill over time. It may be wise to pour some toe walls transversely the width of the drive monolithic with the slab pour if concrete is the route the HO chooses to go. Say 2' deep X 1' wide with rebar or road mesh tieing it to the slab. One of those every 25', or so.



  This is all of course if we are talking very steep say over 12% on up which is 6" in 4'.





 But then maybe I'm rambling on over concerns you are not looking for answers to.



Gordy

meplumber

We didn't.

A few years back, almost 10 now, we did 6,500 +/- sq ft of parking lot for a hospital. It had about an 8% slope from the upper lot to the lower lot that was causing problems to pedestrians. We had asked for under slab insulation, but the site contractor had second thoughts.



A civil engineer was consulted and was also concerned. We ended up not insulating and tying the 22,000'+ of tubing to the wire and a series of cold and hot lifts were done when the asphalt was lain. The site is primarily bedrock so it does act as a heat sink of sorts.



The job works amazing. However, there is really no huge concern with super efficiency. The hospital's boiler plant is sitting on excess capacity. The snow melt load actually helps prevent short cycling on the system.



Yes they need new, smaller boilers since a mechanical overhaul decreased steam loads. However, I don't think they are gonna throw away those 20 yr old Cleavers anytime soon.



Good Luck. Let us know how it comes out.

NYplumber

Creep

Gordy, thanks for rambling. You covered multiple other scenarios. Creep was the issue I was concerned with. Concrete is the material to be poured.



A civil engineer will get me the answer after seeing the job in question.





Meplumber, im dealing with a residential customer who won't run off "extra" heat since there isn't any. Summer, with all that heat under the blacktop, the parking lot turns into a collector.

Gordy

Soil conditions

One thing I did not mention was the fact that soil condition need to be taken into consideration. Virgin ground, or disturbed ground. Predominately wet, or dry. Clay, or granular material. Its good that a civil engineer may be involved. The soil conditions will reflect the spacing, and size of toe walls needed. A key area will be were the driveway ties into the street or road, and where the drive may transition to level or there abouts from slope. That area will need a toe wall also.  Do not forget proper drainage.  I know your just doing the snowmelt, but all these things can lead to failure of the system on your end down the road from shifting/ heaving slab sections.



Gordy 

Mark Eatherton

Another thing to consider....

is where the melted snow is going to flow to. I've seen pictures from the Utah area whereby they didn't take this into consideration, and the ICE hump that got built up due to the melted snow refreezing was so bad, that the HO kept getting high centered in his 4 wheel drive vehicle... Make sure you cover this need contractually, or it may come back to bite your wallet.



As for insulation on a slope, I'd consult an engineer, and take the target off of your back. Again, cover your butt with verbiage on paper, or it too may come back to bite you.



ME

NYplumber

Drains

There will be sufficient drainage.

Most don't account for it.