Clay Roof Underlayment - Roofing Talk

Mike Lamb · 01-02-2009, 07:45 PM

Looks like clay on top of an old 3 tab asphalt. There is an apparent roofing underlayment under the clay and on top of the old roof. I know the clay roof is only as good as the underlayment. What are your thoughts on this installation?

Ed the Roofer · 01-02-2009, 10:35 PM

Is that a 2nd asphalt shingle roof on top of the visible 3-tab, or a 90# granulated roll roofing material in place?

It would seem, due to the severity of the moss build-up along the tile enclosures, that there is not sufficient slope to allow the water to drain properly, or that the overhanging edge of those 3-tabs are curling up, preventing the drainage into the gutter.

Otherwise, there may be moisture getting under the tile roof on a continuoing basis, creating that effect.

That is not how I would install such an expensive roof material on an inferior substrate and uneven moisture barrier underlayment.

Ed

English Roofer · 01-03-2009, 05:37 AM

Hi MIke, some interesting photos!, as Ed says it looks like theres not enough overhang in to the gutter of either the asphalt or the tiles, the minimum overhang of the tiles should be at least 50mm(2") what is happening is the water is dripping off the end of the tiles and running back on its self(Capillary Action).
If you can get on the roof try removing some tiles further up the roof and see if there is any water penitration there, if not your only problem is extention the botton few courses of tiles down further in to the gutter and maybe use some torch on felt made in to drips in to the gutter, hope this makes sence.
Cheers
Dave

P.S. Its a shame because the tiles look good!

Mike Lamb · 01-03-2009, 12:22 PM

I was looking through the NRCA and could not find a spec on tile overhang. This roof had about a 1" overhang. Does it matter if there is a gutter?

English, do you have a reference for the 2"? I also realized after reading the NRCA that this is a cosmetic roof since the pitch is less than 4:12.

Grumpy · 01-03-2009, 01:19 PM

It does look like shingles. In the old days clay roof underlayment was actually smooth bur. Perhaps they used a granulated cap sheet with the smooth bur?

Naaa... chances are some hack installed the tile over shingles LOL. Look at the old gutter straps, those are always a problem for ice damning.

I'm an advocate of always tearing off before installing new when ever possible. However if they wanted a warranty I wouldn't install the tile over shingles.

I did install solar roofing tile once over a fire rated self adhering modified. We used FR because the solar tiles are pretty much constantly at 200* F.

You can go to Ludowici's website or US tile or any other tile manufacturer to get a spec. I might have the Nation Tile Institute's manual which at one point 2 or 3 years ago was available for download but now you have to buy it. I'll have to look for it.

Grumpy · 01-03-2009, 01:20 PM

BTW when you repalce that roof, install a new "high back" gutter.

English Roofer · 01-03-2009, 01:22 PM

Hi Mike, the following is from www.monier.co.uk, which is a large clay tile producer in the U.K.

How much should an eaves tile overhang into a gutter?
With most interlocking tiles it is possible to set out the spacing of the battens to ensure a whole number of tile courses in any rafter length except for very short distances between fixed points. Tiles should not overhang gutters by more than 50 mm measured horizontally from the fascia board. Overhangs greater than this will result in rainwater running off the tiles overshooting the gutter. In addition, cleaning the gutter becomes extremely difficult. If the overhang is less than 50 mm the rain is likely to be blown onto the underlay and accelerate its decay. In addition, the eaves course is likely to sprocket as the weather bars at the tail of the tile will lift the tile off the fascia board.

Hope this helps
Dave

tinner666 · 01-05-2009, 06:46 AM

1-1/2" is the minimum I've used for years. In the states, it's become normal to see the decking stop behind the fascia. It used to uverhang the fascia like it's supposed to, to alleviate capillary actions. I usually pull the bottom plank and set it out 1/2".

carlsguide · 02-27-2009, 10:30 AM

I agree with English Roofer.

tinner666 · 02-27-2009, 07:59 PM

Wow.

I jusr read my earlier answer. I must have gotten confused by reading 2-3 forums at once.
I have been setting tiles between 1-1/2 and 2". Some real life situations have dictated slight changes to go with the flow.

Thanks for the correct answer Dave.

01-02-2009, 10:35 PM	#2
Ed the Roofer Super Moderator Join Date: Sep 2008 Posts: 503	Is that a 2nd asphalt shingle roof on top of the visible 3-tab, or a 90# granulated roll roofing material in place? It would seem, due to the severity of the moss build-up along the tile enclosures, that there is not sufficient slope to allow the water to drain properly, or that the overhanging edge of those 3-tabs are curling up, preventing the drainage into the gutter. Otherwise, there may be moisture getting under the tile roof on a continuoing basis, creating that effect. That is not how I would install such an expensive roof material on an inferior substrate and uneven moisture barrier underlayment. Ed __________________ Just Wait A Minute, I Will Be Right Back With A Link For That. http://www.rightwayroofingcompany.com/ www.rightwayroofingcompany.com Roof Estimates, Roof Repairs, Roofers, Roof Leak Help, Elgin, Carpentersville, East Dundee, West Dundee, Sleepy Hollow, Algonquin, South Elgin, Huntley, Lake In The Hills, Illinois Last edited by Ed the Roofer; 01-03-2009 at 07:18 PM.

01-03-2009, 01:19 PM	#5
Grumpy Senior Member Join Date: Oct 2008 Location: Chicago, IL Posts: 464	It does look like shingles. In the old days clay roof underlayment was actually smooth bur. Perhaps they used a granulated cap sheet with the smooth bur? Naaa... chances are some hack installed the tile over shingles LOL. Look at the old gutter straps, those are always a problem for ice damning. I'm an advocate of always tearing off before installing new when ever possible. However if they wanted a warranty I wouldn't install the tile over shingles. I did install solar roofing tile once over a fire rated self adhering modified. We used FR because the solar tiles are pretty much constantly at 200* F. You can go to Ludowici's website or US tile or any other tile manufacturer to get a spec. I might have the Nation Tile Institute's manual which at one point 2 or 3 years ago was available for download but now you have to buy it. I'll have to look for it. __________________ -Grumpy Chicago Gutters Chicago Roofing

01-03-2009, 01:20 PM	#6
Grumpy Senior Member Join Date: Oct 2008 Location: Chicago, IL Posts: 464	BTW when you repalce that roof, install a new "high back" gutter. __________________ -Grumpy Chicago Gutters Chicago Roofing

01-05-2009, 06:46 AM	#8
tinner666 Slate and Metal Roofer Join Date: Oct 2008 Posts: 142	1-1/2" is the minimum I've used for years. In the states, it's become normal to see the decking stop behind the fascia. It used to uverhang the fascia like it's supposed to, to alleviate capillary actions. I usually pull the bottom plank and set it out 1/2". __________________ SLate Repairs, Richmond, Va. Contractor Domain Name Sales Yes, I Sell them. DIY Roof Help Richmond, Va. Tinner666 Window Flashing Tutorial

02-27-2009, 10:30 AM	#9
carlsguide Junior Member Join Date: Feb 2009 Posts: 3	I agree with English Roofer. __________________ new roof cost and other home renovation cost estimates

01-03-2009, 05:37 AM	#3
English Roofer Roofing Expert Join Date: Dec 2008 Posts: 104	Hi MIke, some interesting photos!, as Ed says it looks like theres not enough overhang in to the gutter of either the asphalt or the tiles, the minimum overhang of the tiles should be at least 50mm(2") what is happening is the water is dripping off the end of the tiles and running back on its self(Capillary Action). If you can get on the roof try removing some tiles further up the roof and see if there is any water penitration there, if not your only problem is extention the botton few courses of tiles down further in to the gutter and maybe use some torch on felt made in to drips in to the gutter, hope this makes sence. Cheers Dave P.S. Its a shame because the tiles look good!

01-03-2009, 12:22 PM	#4
Mike Lamb Junior Member Join Date: Nov 2008 Location: Chicago Posts: 7	I was looking through the NRCA and could not find a spec on tile overhang. This roof had about a 1" overhang. Does it matter if there is a gutter? English, do you have a reference for the 2"? I also realized after reading the NRCA that this is a cosmetic roof since the pitch is less than 4:12.

01-03-2009, 01:22 PM	#7
English Roofer Roofing Expert Join Date: Dec 2008 Posts: 104	Hi Mike, the following is from www.monier.co.uk, which is a large clay tile producer in the U.K. How much should an eaves tile overhang into a gutter? With most interlocking tiles it is possible to set out the spacing of the battens to ensure a whole number of tile courses in any rafter length except for very short distances between fixed points. Tiles should not overhang gutters by more than 50 mm measured horizontally from the fascia board. Overhangs greater than this will result in rainwater running off the tiles overshooting the gutter. In addition, cleaning the gutter becomes extremely difficult. If the overhang is less than 50 mm the rain is likely to be blown onto the underlay and accelerate its decay. In addition, the eaves course is likely to sprocket as the weather bars at the tail of the tile will lift the tile off the fascia board. Hope this helps Dave

02-27-2009, 07:59 PM	#10
tinner666 Slate and Metal Roofer Join Date: Oct 2008 Posts: 142	Wow. I jusr read my earlier answer. I must have gotten confused by reading 2-3 forums at once. I have been setting tiles between 1-1/2 and 2". Some real life situations have dictated slight changes to go with the flow. Thanks for the correct answer Dave. __________________ SLate Repairs, Richmond, Va. Contractor Domain Name Sales Yes, I Sell them. DIY Roof Help Richmond, Va. Tinner666 Window Flashing Tutorial

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