Concrete Screw into Concrete Roof Tile 2

[jefftsolar]

I'm trying to empirically prove the strength of a concrete screw into a typical concrete roof tile. Here's the technical data of the concrete screw I want to spec.

http://www.concretescrews.com/technical-info/tapcon-concretescrew.aspx

I've been informed that concrete tiles are usually 1" thick, however, I am not sure if I should treat it like lightweight concrete (2000 psi) or as a CMU block, or perhaps not even able to empirically prove it without knowing the manufacturer of the concrete tiles.

Seeking advice in this situation, or perhaps supporting information in regards to standards on manufacturing concrete tiles. Any help will be greatly appreciated.

 

[hokie66]

Concrete roof tiles are cladding, not something you should be screwing to for structural purposes. I have never seen concrete tiles that are as thick as 1". What possible reason could you have for doing this?

 

[azcats]

My bet is on solar.

 

[Ron]

Ok...let's start with a few assumptions...please confirm.

1. You are wanting to attach solar panels to concrete roof tile using Tapcons.
2. You want to prove that the pullout of the Tapcons in the roofing tile is sufficient to resist the uplift of the solar panels.

Concrete roof tiles are not 1" thick consistently. They are cast in a mold and are thicker on the edges than in the middle. Check out a few concrete tile manufacturer's websites and you'll see the configuration. Given that, you won't get 1" embedment of the Tapcon.

Next, roofing tiles are not designed to have stuff attached to them. They have enough trouble resisting the uplift moment alone without something else pulling on them as well.

If you attach something to a concrete roof tile and let's say you have a 200 lb resistance from the fastener embedded in the tile. First of all, most codes will only allow you to count 25% of that pullout resistance since it is a fastener in direct tension.

Further, let's consider that the fastener ends up being 10" down from the leading edge (tail) of the overlying tile. The fasteners holding the tile to the roof are another 2" or so under the tail of the overlying tile. Now you have a moment arm of 12" on the 200 lb uplift, or 2400 in-lbs of moment on that tile....won't take it.

Bottom line...don't attach anything to a concrete tile for uplift. Go through the tile and into the deck, but DON'T compromise the waterproofing.

 

[hokie66]

I wouldn't allow screwing to or penetrating concrete roof tiles. The brackets can be screwed to the tile battens, and then the tiles reset without penetration.

 

[MiketheEngineer]

I think Ron has it about right.

Some companies will - for a fee - test them for you.

But if it is roof tile - forget it. All you will have are solar panels on the ground with the tiles still attached.

 

[jefftsolar]

Appreciate the advice on this project, and yes, this is a solar panel project for mounting on a flat or barrel tile roof.

 

[ToadJones]

I wouldn't dream of putting a Tapcon into a concrete roof tile. Amongst that which has already be said, you may split the tile.