Concrete Footing over Asphalt+foam layer

LegeLege Registered Users Posts: 3
Hi everyone,

I was wondering what If I placed concrete footing for solar arrays over asphalt layer which has below it a foam layer,
what about the bonds between the concrete and asphalt??? and the stability???

Thank you in advance.

Comments

  • sunbunnysunbunny Solar Expert Posts: 59 ✭✭✭✭
    Re: Concrete Footing over Asphalt+foam layer

    Why would you want to do that ?

    Is this an array that is sitting on the ground ?

    Stability depends on weight and leverage and wind loading.
  • BB.BB. Super Moderators, Administrators Posts: 32,611 admin
    Re: Concrete Footing over Asphalt+foam layer

    There is an installation method that just uses weight to hold an array down... Basically the weight has to be higher than the wind loading (used on flat roofs and some ground mounts). There is always the question of the ability of the roof to support the weight and how much weight (calculation of wind loadings).

    Not enough weight, and the array goes traveling/overturns.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Concrete Footing over Asphalt+foam layer
    Lege wrote: »
    what about the bonds between the concrete and asphalt???

    I don't think the bond between ashfalt and concrete matters. You either need to dig through and put some sort of posts, or relay entirely on the weight of the concrete. Very heavy weight may damage ashfalt.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Concrete Footing over Asphalt+foam layer
    BB. wrote: »
    There is an installation method that just uses weight to hold an array down...

    That method is often (usually?) called "ballast mounting". --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Concrete Footing over Asphalt+foam layer

    I can tell you that if its a permitted job it won't pass. Even if you are just using the concrete as a a counter weighted method against wind sheer, most engineers and inspectors frown upon the lack of insufficiency, in doing the work as a form of "means and methods", kind of like an instruction manual with calculations in an engineering blue print. If its grid tied and looking to get state rebates, or tax credits, the "lack" of means and methods will prevent you from collecting.

    Mentioning anything of "foam" composite scream that the below grade condition is not stable for the weight, and should be done correctly.

    The proper way to do it is to excavate and engineer accordingly so that it is defined as an "underpinning", or "footing", according to engineering definition.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Concrete Footing over Asphalt+foam layer
    Even if you are just using the concrete as a a counter weighted method against wind sheer, most engineers and inspectors frown upon the lack of insufficiency, in doing the work as a form of "means and methods", kind of like an instruction manual with calculations in an engineering blue print.

    Do you think you could rewrite that part at least to make it clearer as to your meaning?
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Concrete Footing over Asphalt+foam layer
    Do you think you could rewrite that part at least to make it clearer as to your meaning?

    Sure.

    So to start, I don't think any engineer, or contractor in this forum would assume to say that it is O.K, or safe to just apply concrete on top of a foam, or asphalt composition layer. Nor do I think that even for a roof counter weight "ballasted system" would adding blocks to a solar system for counter weighting is OK without a full inspection, with calculations for that roof load, (I.E) according to specs for roof loads first the lumber type, and grade has to be determined being that of STD grade 1 or grade 2 which is a measure of density specific lumber,as well the width and lengths of that lumber, and structural layout. (I.E) in the case of a ground mount system most systems installed require what is called a core drill sample, that typically can be drilled from 3' to 15' in depth depending on the size, weight, capacity and wind sheer factors of that system. The core drill samples are sent off to an engineering firm that records the density of the soils there are 3 types of soil grades ranging from class A, B, and class C, construction 101 basics in construction management, and OSHA highlight these soil grades for level of safety. Engineering firms take the layers of soil to determine how dense the soil layers are. Then depending on the density of the soils, a depth for either 3 types of foundation and/or counter weighted system become applicable. Either (1) a footing type system, or (2) a underpinning type system, or (3) ballast block system.

    The type of foundation and/or ballasted system that will be determined comes from the engineering firm, which then like an instruction manual, lays out the foreground for the installation in either a cut sheet, spec sheet, blue print, etc... Those instructions loosely base "method" of installation unless detailed that a method must occur, so installer can anticipate those cost impacts. Method is a system of delivering the requirements for building that particular "spec" being human resource such as digging with a shovel, or using minimal human resource, by implementing auguring equipment. "Means" in essence is quality control during the duration of a construction build, it is a level of anticipation according too, and adversely effecting "method", and in most cases lays out for the installer, or contractor what it will take to get the project done effectively, in a timely manner, and to follow the requirements of the engineering specs. "Means" is the anticipation of sourcing either product or product grades, if, or if not specs aren't provided, or sourcing time management, and or supply chain sources. Unless specified from engineers what type of "grades" to be used, (I.E) a 5/8" bolt isn't just a 5/8" bolt according to different ASTM, without a verified spec its arbitrary what to source, this effects quality, safety, and life of the product. Means and Methods of construction is as to a cause and effect of a scenario.

    Now Lege asked a question, I will not answer or entertain for my level of professionalism. I have no clue of the size of the system, nor do I have specs, but to say the least for long term prospects, I can say just pouring concrete and applying additional loads to foam and asphalt, is not a good idea.

    Asking that type of a question in a forum such as this, means the person asking the question needs to do a lot more research, get a professional out to the property to take a look if he/she doesn't know the answer them self because the realm of physical conditions only pertains to the person that started this thread. Also take note, footings and underpinnings are sub grade installations, not on top of a grade installation. As Vtmaps pointed out ballasting is a top grade installation, so the thread starter is using incorrect terms.

    My largest concern, divulging a incorrect answer to an incorrect question, can led to safety issues, that can cause serious injury, death, or early product failure. In any matter I chose not to entertain Lege's question any further, because the liability implication does have its impacts.
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