Downspout discharge onto slate roofs

[Michael Thomas]

Don't see a lot of slate in my area, so two quick questions about this new construction slate roof

Q1. To what extent (if at all) should I be concerned about direct downspout discharges downwards across the shingles in a vertical direction at slate roofs (see 1st attached picture).

Is there a significant likelihood of eroding the slate (as is the case on a convention shingle roof), or is this a non-issue on a slate roof?

Q2. To what extent is it an issue if the discharge is *across* the shingles (see 2nd attached picture).

Is there a significant likelihood of water penetrating under the shingles where discharge is crosswise to the vertical edges of the shingles?

I notice that someone has applied sealant between the tiles immediately below the discharge.

Standard procedure? Kluge? Idiocy? (I would think that if anything you would want to interleave copper flashing below the shingles in this area, as it would only be visible at the gaps between the tiles...)

Q3. If these are significant concerns, is there an industry source I can cite when discussing such discharge?

Thanks as always.

[Raymond Wand]

Its of such short distance to the lower gutter in my opinion I don't think it would be troublesome other than the downspout discharge overshooting the lower gutter.


Found this site for you interest.

Roofing Slate | Some facts on roofing slates (http://roofingslate.wordpress.com/)

[Mike Kleisch]

I would turn the one downspout downhill, and maybe install something like in the photo.

[Mike Lamb]

ASHI article should read: http://www.traditionalroofing.com/downloads/ASHI_article_4_05.pdf

The sealant at the tiles next to the sideways downspout elbow says trouble. Water may be entering the slate nail holes.

Another good reference: Slate Roof Central - How to Install a Traditional American Slate Roof (http://www.slateroofcentral.com/install.htm)

[tom daley]

There's no chance of slate erosion but best practice is to point the discharge down the plane of the roof.
There is a possibility of moisture penetration when discharging across the plane.
Maybe (as mentioned above) they pointed the elbow across the "grain" to prevent any possible overshooting over the nearby gutter?

As also mentioned, the caulking of the slate is definitely bad practice - the slate bond is irregular
and a length of "ripped" slate is missing.

Slate should be supplied in modular sizes, only using random sizes when specifically specified eg. to achieve some kind of traditional "cottagey" look.

Rather than "interleaving" copper soakers under the slate in the at risk area, perhaps, a simpler solution would be to, as mentioned above, point the discharge downhill.

[tom daley]

The problem with an improvised chute, such as the one in the Mike Kleisch pic, is that there is no method or fixing the device in a secure and watertight manner. Hence, there is a possibility of the chute being lifted & blown off the roof.
From a safety point of view, i would consider it a risky method.
Fixings through the roof plane would also introduce more penetrations of the roof coverings.
Plus, there is the possibility of introducing overshoot at the gutter (although a kick-out would help but where do you stop improvising), or jetting water out from the eaves if no gutter is present.