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February 12, 2023 at 3:07 pm #207120
Quick question from a customer in Boston. Client wants a batten system over a solid deck for increased breathability. They are going to use 5/4” x 6 battens, but asking what type of wood is generally most used for something like this. The 2010 manual only says “nominal lumber”.
Just looking for a general consensus and will not offer any “recommendations”. I will just say that XYZ lumber would be most commonly used from the guys that I talked to.
Thank you in advance.February 13, 2023 at 11:10 am #207124
Battens aren’t very common in the US. In New Orleans, all the old tile roofs used Cypress. We’ve used Cedar, but I don’t know if there’s a standard?February 13, 2023 at 4:11 pm #207126
I have only seen one true venting slate system over a solid roof deck. To allow this to vent there needs to be vertical battens and horizontal battens. This makes the dry in very difficult, unless the battens are uncovered on top of the dry-in. The roof was a mansard with a flat roof on top. The roof vented into the attic space and the air was then vented thru several large 4’x 4’ chases that went all the way to the basement, three and ½ stories. The chases also pulled air out of the entire house. On a hot day there was air flow coming in all open windows. It was an amazing system.
The building was the Nemours Mansion in Delaware built-in 1910.February 14, 2023 at 7:12 am #207128Watsky, RusselParticipant
I thought Clay’s client was asking about venting of the underside of the deck. So I was picturing battens running vertically 16” on center. Then plywood sheathing as the new deck to support the slate. There would be provision for fresh air intake at the eave, and a venting ridge detail. This would provide airflow under the new plywood deck. I don’t think they intended to vent the whole house.February 14, 2023 at 12:13 pm #207131
These battens are completely on top of the boarded deck, but I can understand Russ’ confusion about “extra ventilation” (just poorly worded on my part). Just extra ventilation underneath the slate. Not exactly sure why altogether.
They will be using vertical battens and then horizontal ones on top. And I agree Alan, that waterproofing the roof deck becomes a bit more difficult.February 15, 2023 at 10:13 am #207133
I assume that they’re trying to go with what was traditionally done in many of the European countries. They install vertical battens (on top of the underlayment) on top of the rafters. Horizontal battens go on top of the vertical battens, and the slate/tile is nailed into the horizontal battens or lugged in on a tile roof. It keeps the slate/tile dry and allows for ventilation and moisture runs out the bottom. Many of these old historic buildings had no roof deck.
My guess is that this allows for the slate and tile roofs to last hundreds of years – even with lower grade slate/tile.February 15, 2023 at 3:15 pm #207135Cornwell, DanParticipant
We use batten and counter battens on tile roofs always. Same difference for slate. Fir is probably best, don’t use cedar over a counter battens it does not have enough strength, but it is more moisture resistant if placing it direct on the deck. Pressure treated is OK but, in my mind, not mandatory as once battens are elevated, they don’t pond water even with broken slates above and are protected from UVs by the slate with air movement around them. As far as strength, if using counter battens the closer you put counter battens together the less deflection on the batten and the greater strength. I really like the Boral (now Westlake) Elevated ax3 battens as they have supports every 12 inches so almost no deflection and no bonce when nailing.
Here is a photo of job we are doing on Mt Hood it has PT 2×4 counter battens 16” on center vertical, a draped underlayment over those and Pt 2×4 horizontal battens with inch thick slate. This sometimes gets 12 feet of snow. It also has highly permeable Vapro Shield self-adhered membrane under the counter battens. We got snowed out so going back in April or May when it melts.
Also here is a batten span chart from the 2002 Tile Roofing Institute Moderate Climate Manual which I helped with the writing.
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