Author Topic: Venting configuration question  (Read 6581 times)

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Pa_Kettle

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Venting configuration question
« on: October 23, 2006, 05:53:23 AM »
Still working on the Little House here.  I'm planning on running the exterior wall sheathing all the way up until it hits the underside of the roof sheathing.  I'll punch holes in this wall sheathing and put the typical vent/screen up for venting.  Of course I'll have to notch the sheathing around the rafters, but  I don't see any big deal with that.

Any problems I should be aware of in doing things this way?  I'll probably run some sealant at the roof/wall junction to keep most critters out.

Thanks,
PK


jraabe

  • Guest
Re: Venting configuration question
« Reply #1 on: October 23, 2006, 01:35:34 PM »
No real problem there. If you do blocking between the rafters and nail the sheathing panel to it it will serve to tie the wall and the roof together. If you do this before sheathing the roof you can use a skillsaw to cut a couple of notches in the blocking for ventilation and cover this with screen before sheathing the roof.


Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #2 on: October 23, 2006, 02:17:03 PM »
Sounds good.  Thanks for the quick reply.

The way we added the rafter tails gives me the end of the true rafters (clipped flush to the wall) to nail the wall sheathing to.  So I think I can tie the wall and roof together fairly well that way.

I think I'm going to leave the vent openings for later.  We won't have the structure insulated anytime soon, but we may try to heat it while working.  I figure I can hole saw from the inside-out and add those circular vents when needed, just before insulating the roof.

Thanks again,
PK


peg_688

  • Guest
Re: Venting configuration question
« Reply #3 on: October 23, 2006, 08:19:10 PM »
Pa why not drill the holes in the 2 by blocking before you put them up. Then later you can just finish the hole thru the 1/2" sheathing.

 Running a 1/2" drill motor off a ladder or all squated / scrunched down is no fun and with a hole saw dangerous as well.

  Another suggestion would be to install your blocking 90 deg. from the top of your rafter and flush  the inside of the block with your exterior sheathing so it becomes a trim piece to side to. The hurricane clip will tie your rafter down just as well.  This image shows the block flush outside of block  to outside of framing . If you flush the  inside of the block with the outside of sheathing you end up with a 1 1/2" trim piece to side up to.

 If you want to heat the place stuff a wad of insulation in the vent hole for the time being.

  

  You can and should IMO put the clip on the inside , this  photo was the only one that showed the block and rafter. It (the clip  in this image ) is a H10 , more than likely a H1 or H2.5 will be all you need.

 This is a poor image as it does not show a birds mouth cut on the rafter. But it does show the basic block detail.

 Your way is a lot more work for little gain in strength.

 G/L either way, PEG  

Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #4 on: October 24, 2006, 09:21:44 AM »
I don't have blocking between the rafters nor am I running the clips.  This is why I plan to just run the OSB up to the roof sheathing.   I'll tie it into the rafter ends as well as the loft joist ends to tie the walls to the roof.

Then, when I need to add venting I can just hole saw through the OSB from the inside.

Am I way off base doing this?  I guess that was my original question.

PK


jraabe

  • Guest
Re: Venting configuration question
« Reply #5 on: October 24, 2006, 02:59:19 PM »
You are plumb cutting the rafters so the sheathing will climb up to the top of the rafter right?

If you are not using blocking to space the rafters do they just sit on the plate and get toenailed in?

The blocking goes a long way towards helping to tie the wall and rafters together.

Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #6 on: October 24, 2006, 05:36:10 PM »
Quote
You are plumb cutting the rafters so the sheathing will climb up to the top of the rafter right?
Yes, the rafters are plumb cut and then 2x4 "tails" have been added on for overhang.

Quote
If you are not using blocking to space the rafters do they just sit on the plate and get toenailed in?
Yes, the rafters are toenailed, and most are face nailed into the adjacent loft joist which is also toenailed into the top plate.

Quote
The blocking goes a long way towards helping to tie the wall and rafters together.
For most of the rafters there is a tail slabbed to them and a loft joist on the other side.  I couldn't nail through all three into the blocking.  So, the blocking would only be nailed straight down into the top plate and then the wall sheathing into the blocking.  I can't see this adding up to much more than a taller top plate.  Also the rafters are not 3.5" tall at the outside edge of the top plate.  So I would be ripping 2x4s along the edge to get them the right height.  I'd also have to cut that long cut at a 45 (or 130) degree angle to match both the roof and wall.

I'm not trying to be obtuse here, I'm just not real clear on how the blocking will help tie the wall to the rafters.  I can certainly see how it would help space the rafters if loft joists weren't in the equation.  I will install hurricane ties on the inside of the wall if that makes good sense.

Thanks for all the help so far.  :)

PK


peg_688

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Re: Venting configuration question
« Reply #7 on: October 24, 2006, 06:32:53 PM »
Humm you may have taken a , ah , alternative path. So you have a scabed on 2x4 rafter tail instead of rafter tail cut on your accual rafter it sounds like  :-/?

 Anti rotation blocks are standard equip. here in the eathquake prone  ::) PNW . A generally every where I've built . If you have not insp. to pass your idea MTL will work.

 My advise had a block ,2x material, in place and a rafter tail that was cut on the rafter, what I did on my last job was cut the joist 3" short , leaving it 1 1/2 " back from framing on both ends for the  anti- rotation block to butted to it , the blocking. This still leaves the joist bearing on 4" of top plate.

 Anyway all water under the bridge for you . G/L PEG    

Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #8 on: October 25, 2006, 05:56:11 AM »
Quote
Humm you may have taken a , ah , alternative path. So you have a scabed on 2x4 rafter tail instead of rafter tail cut on your accual rafter it sounds like  :-/?
Yep.  I followed the description straight from the Little House plans.  I liked the idea because I got to make simpler cuts (no birds mouth) and I could use 10' boards.  I had to lift these critters by myself into place, so the shorter the better.

Quote
Anti rotation blocks are standard equip. here in the eathquake prone  ::) PNW . A generally every where I've built . If you have not insp. to pass your idea MTL will work.
I'm googling anti-rotation blocking, but not getting anything descrbing it.  What does it do in case of earthquake?  What does MTL mean?  :-?

Quote
My advise had a block ,2x material, in place and a rafter tail that was cut on the rafter, what I did on my last job was cut the joist 3" short , leaving it 1 1/2 " back from framing on both ends for the  anti- rotation block to butted to it , the blocking. This still leaves the joist bearing on 4" of top plate.
Makes sense.  Did you nail through the rafter into the end of the blocking or just face nail through the blocking into the end of the joist?

Quote
Anyway all water under the bridge for you . G/L PEG    
Well, I don't want to do anything really wrong here.  If I can go back and do some extra work to fix something, even in a non-conventional way, I will.

Thanks for the info.

Pk


glenn-k

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Re: Venting configuration question
« Reply #9 on: October 25, 2006, 06:11:47 AM »
Hi PK.  Sounds like you are coming along on your project.

I used the clipped rafter detail on my RV garage also then changed the pitch for the wraparound porch roofs.

MTL is more than likely.  

I think the anti-rotation blocking is just the horizontal blocking at the edge between the rafters as shown in the above clip installation illustration.  An earthquake would try to hinge your rafters and rip them loose at the top plate connection.  Without the block the sheathing would not do much to stop it.  The block will keep them from rotating.  While a bit more complicated to lay out, I don't see why you couldn't just make your blocks full rafter to rafter distance and notch then out as necessary to leave room for the rafter tail.

 

« Last Edit: October 25, 2006, 06:13:33 AM by glenn-k »

jraabe

  • Guest
Re: Venting configuration question
« Reply #10 on: October 25, 2006, 07:03:39 AM »
OK, now I see... you have put up the eave extensions shown in your photos here: http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1150900056/20

I would use the extended blocking detail on page 5 of the Little House plans and put in the optional blocking shown (flat 2x4). This will brace the rafter and provide the additional roof to wall sheathing connection. The 2x4 vented blocking can be done later but works best if the roof sheathing is nailed into it. This provides the anti-rotational thing PEG is arguing for.

« Last Edit: October 25, 2006, 07:24:30 AM by jraabe »


peg_688

  • Guest
Re: Venting configuration question
« Reply #11 on: October 25, 2006, 10:26:47 AM »
Humm I didn't think I was argueing , just explaining  :-? Or tryin to  :-[ The block shown in the Simpson image with the H10 attached to it would be a anti rotation block , a un vented one as it has no vent hole . It would keep the rafters from rolling over in a quake , or so they say  ::) I guess we'll see next time we have a big um  :o

  MTL = more than likely , I hate blanket statements as there is MTL more than one right / wrong / another way etc to do almost anything . Or in most cases it's my way or the highway  ;D

  The way I think your talking about doing your sheathing witha knotch cut out for the rafter it would in a way be anti rotational , although thin 1/2" as apposed to  2x framing member. It would not pass code here but MTL would be fine in almost every situation your lil cabin will encounter so carry on as you where.

 As John has said you really have to work at building something that will fall down  ;D But we all build with thoughts of long life for our building or should IMO.

 G/L PEG , Sorry if I sounded arguemenative  :-[

Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #12 on: October 25, 2006, 11:29:56 AM »
LoL, peg.  I think John was using arguing in place of "advocating".  I think... :-?

Anyhooo, I think I have a handle on what the issues are now.  I will certainly post info about whatever mods I make to this wall/rafter interface.


Cheers

PK

jraabe

  • Guest
Re: Venting configuration question
« Reply #13 on: October 26, 2006, 01:22:32 PM »
We all appreciate PEGs advocacy for his point of view!  :D. That's why he's a GOD member!  :-*


peg_688

  • Guest
Re: Venting configuration question
« Reply #14 on: October 26, 2006, 07:46:10 PM »
Quote
We all appreciate PEGs advocacy for his point of view!  :D. That's why he's a GOD member!  :-*


 Glenn said it's cuz I talk/type  to much ;D

glenn-k

  • Guest
Re: Venting configuration question
« Reply #15 on: October 26, 2006, 07:56:56 PM »
You're OK by me, PEG.  












Nearly all the time. ;D

Pa_Kettle

  • Guest
Re: Venting configuration question
« Reply #16 on: October 31, 2006, 06:58:23 PM »
Ok ok ok... The whole wall sheathing up to the roof sheathing thing was pure folly.  I failed to realize 7/16 OSB should be considered more of a "skin" than a "board"  It works great only when nailed across framing members.  I also forgot that I don't have loft joists on both side of each rafter, so the wall sheathing only had one joist to nail into.  The other corner of the sheathing would just be relying on its own stiffness to stay vertical.

So, I ran the OSB flush with the top of the top plate.  I'll run Simpson clips on the inside of the wall and run blocking as described in the plans.  I don't think I'll do the optional blocking though.


PK


peg_688

  • Guest
Re: Venting configuration question
« Reply #17 on: October 31, 2006, 07:24:07 PM »
Should I gloat now ;D ;D

 I'd still advocate  ;) for the blocking.

 Oh Lord it's hard to be humble;;;;;;; ;D ;D

glenn-k

  • Guest
Re: Venting configuration question
« Reply #18 on: November 01, 2006, 05:46:21 AM »
PEG, you're such a brat.   Always gotta have your way.   --- Who was that? :-/  Mom --- is that you? :)

 

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