Venting Tongue and Groove Soffit

[midrover170]

Hi folks. Next question.

I'm planning to install T&G cedar or pine for my soffit. I have a shed roof, so only two areas where venting is really needed (high/low sides). I don't have an attic, just want to properly vent the air space above roof insulation. Does anyone have experience venting such a setup? There are some wood T&G vents out there, but most of the suppliers are in Canada.

Would it be OK to router some slots in one of the runs of T&G and install tight mesh on the back? Other thoughts? Cut circular holes for circle louver vents?

Thanks,
-D

[Redoverfarm]

I think your question just begs for other questions.  Is this a metal roof or shingle?   Are you installing rafter mates as an air channel from the lower to the upper.  Is there an overhang on the upper or ridge portion of the roof?  If it is metal is it installed on purlins or sheeting?

I assume you will running the soffit (T&G) perpendicular to the structure.  If so you can cut to fit any venting grates and the T&G will stay in place provided that the vent fits up into the cavity.  I used T111 on mine and then used a 4X11 metal screen louvered vent with a matching or corresponding color.



I believe that I had once heard for every 100 sq ft of roof area you need 1 sq ft of venting. 

[midrover170]

Hey Redoverfarm,

I think your question just begs for other questions.  Is this a metal roof or shingle?   Are you installing rafter mates as an air channel from the lower to the upper.  Is there an overhang on the upper or ridge portion of the roof?  If it is metal is it installed on purlins or sheeting?

It's a metal roof installed over sheathing. My rafters, 2x12s, extend 2ft past the high/low walls of my shed roofed cabin. My fly rafters are out about 14". I was planning to do the T&G parallel one the high/low ends, and perpendicular on the long rake walls. Cutting the vents in, like you've explained seems like the best option so far.

Here's a pic of the structure.

[Redoverfarm]

Hey Redoverfarm,

It's a metal roof installed over sheathing. My rafters, 2x12s, extend 2ft past the high/low walls of my shed roofed cabin. My fly rafters are out about 14". I was planning to do the T&G parallel one the high/low ends, and perpendicular on the long rake walls. Cutting the vents in, like you've explained seems like the best option so far.

Here's a pic of the structure.

That helps clarify some of my concerns with your original question.

Here is how you calculate what you need

http://www.todayshomeowner.com/adding-soffit-vents/

Here are some various vents available

https://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4TSNA_enUS401US438&q=types+of+soffit+vent

There are various style vents available.  The ones I got are made to fit up into a cutout and have the screen attached (back side)  I guess it really doesn't make any difference what orientation the T&G is but I was thinking it would stay together better perpendicular.  The small roof is going to be difficult to vent.  They do make a vent for shed attachment but you might consider just cutting small diameter holes with a hole saw through the plate and into the sheeting of the main house in the rafter bay area of the small room and then use those rafter mates attached to the inside wall stud area of the outside wall sheeting of the main house to carry the air up to the main roof area. That should not compromise the ledger integrity . I assume it will be covered with insulation anyway.  You would be the only person that would even know they are there.   

[midrover170]

That helps clarify some of my concerns with your original question.

You got me thinking (why I like posting here  ). Since I'd be installing my soffit to the underside of the rafters, that would limit cross ventilation through the rafters bays, right? In other words, only the bay with the vent cut into it would vent... I'm thinking maybe the circular vent in each bay make sense, or I could use a hole saw and drill through the rafters in the soffit area. Maybe I'm looking at this wrong too..

I'm only installing fascia this weekend so I'll take some closeups of the soffit area.

Thanks for all the links.

[Redoverfarm]

You got me thinking (why I like posting here  ). Since I'd be installing my soffit to the underside of the rafters, that would limit cross ventilation through the rafters bays, right? In other words, only the bay with the vent cut into it would vent... I'm thinking maybe the circular vent in each bay make sense, or I could use a hole saw and drill through the rafters in the soffit area. Maybe I'm looking at this wrong too..

I'm only installing fascia this weekend so I'll take some closeups of the soffit area.

Thanks for all the links.

Yes you are correct. Maybe that is why they make a continuous vent to take care of that application.  On mine I had boxed my soffit in so the air moved to the adjoining rafter bay areas.  I doubt that it would hurt to drill the rafters  with a small diameter hole saw to allow that air to migrate to the other bays. Actually one vent could feed three bays then move over and place another to feed three other bays. I am sure you will figure it out.  BTW I got to thinking about my replay concerning the small roof.  I modified that post once I thought about the ledger for the small roof.  But I think it might be a solution to an expensive vent at that intersection. 

Let me know what you decide on.  Good luck.

[Don_P]

Whoops, I was typing slow, I think this is what John is describing.

I usually run the T&G the way you were first describing, parallel on the vented eaves low and high and perpendicular to the wall up the rakes. I use continuous strip vents that are about 3/8" tall x~2" wide with a flat flange on each side. Beginning at the lower fascia I remove the tongue from the first row and face nail with the groove edge against the backside of the fasia. I don't nail along the tongue removed edge yet, leaving room to slip the strip vent in. Working to snapped lines helps with soffit and vent that is running lengthwise, you usually have a sightline right down it and wiggles show. Then slip in the vent, nail the edge nearest it tight. I usually use roofing nails to hold the uphill flange of the vent in line, not nailing the vent but letting the wide head on the roofer hold the flange to the underside of each rafter.. Then rip the tongue off the next row and run the ripped edge against the vent strip, groove uphill, and face nail at each bearing. next row is tongue into groove and face nail, work up to the wall and then with the first short perp piece turn the boards around and workk up the rakes blind nailing the fly edge and face nailing the wall edge, those nails will be covered when you side. Repeat the process at the top.

Those vents can sing in high wind, I think the ones Redover has would probably do the same, the metal vents start vibrating.  I've thought about routing some kind of decorative slots and stapling screen to the backside while installing it but have never gotten the round tuits. If memory serves it's 1/150th for typical construction down to 1/300th free vent area for tight construction. In a cathedral I put chutes in every bay, all the way before insulating to positively maintain the vent channel.

On our sidewall upper vent I took the metal ridge vent, cut off one side but leaving the entire "roof" of the vent, which I bent upright to become a wall flange. It did take a very little water in during a hurricane, water blowing upslope (4/12) and high wind driven rain, it is the weak point in that roof.

[midrover170]

Whoops, I was typing slow, I think this is what John is describing.

I usually run the T&G the way you were first describing, parallel on the vented eaves low and high and perpendicular to the wall up the rakes. I use continuous strip vents that are about 3/8" tall x~2" wide with a flat flange on each side. Beginning at the lower fascia I remove the tongue from the first row and face nail with the groove edge against the backside of the fasia. I don't nail along the tongue removed edge yet, leaving room to slip the strip vent in. Working to snapped lines helps with soffit and vent that is running lengthwise, you usually have a sightline right down it and wiggles show. Then slip in the vent, nail the edge nearest it tight. I usually use roofing nails to hold the uphill flange of the vent in line, not nailing the vent but letting the wide head on the roofer hold the flange to the underside of each rafter.. Then rip the tongue off the next row and run the ripped edge against the vent strip, groove uphill, and face nail at each bearing. next row is tongue into groove and face nail, work up to the wall and then with the first short perp piece turn the boards around and workk up the rakes blind nailing the fly edge and face nailing the wall edge, those nails will be covered when you side. Repeat the process at the top.

Really like the detail and process, Don. If nothing else comes along, I'll go this route. Roof (hopefully) going on next weekend - woohoo!

BTW I got to thinking about my replay concerning the small roof.  I modified that post once I thought about the ledger for the small roof.  But I think it might be a solution to an expensive vent at that intersection. 

I've thought about using a system like this:
https://www.pac-clad.com/wordpress2013/wp-content/files_mf/cache/th_9dfb385cccb5f748bcaf8e3170623ebe_SS-Ridge-Vent-Slope-to-High-Wall_Page_1.png

I think Air Vent makes something similar, and Cor-a-Vent as well. You basically cut a 1" channel in your sheathing, leaving about 6" on the edges. Install the product on top of the roofing system, and you're good for venting. Most are special order though...

[flyingvan]

http://www.owenscorning.com/NetworkShare/Roofing/Images/For_OC.comOnly_Mini-Round-Louvers.jpg

Drill it out, Pop them in.

[MushCreek]

I used the round vents- 4", one per bay, with a ridge vent. Tip- Figure out which plank will have the vent and drill them before installing. Wrestling a 4" hole saw upside down, on a ladder ain't fun.

[midrover170]

Thanks, everyone.

I was able to install the fascia boards over the weekend (on the main roof) using a handy tip from this video:
https://www.youtube.com/watch?v=YZLJKyktEsc

I was working alone so no way I could have done without the jigs. Couple pictures below. Soffits are a few weeks/months out. Roof is going on next weekend, and windows sometime in between.