Framing cathedral ceiling

[Bart Marek]

I’m framing 17x10 room addition to the side of the house I want to do cathedral ceiling. So far I got plans for triple 2x12 ridge beam supported on house end by three 2x4 in the existing outside wall and three 2x6 on the other end, where wall is 6 inch. Rafters to be 2x10 that should give just enough room for R30 insulation (http://www.inspectionnews.net/home_inspection/newthread.php?do=newthread&f=18) and little space for ventilation. The plans I have are not for exactly the same size addition so I’m wondering if I could go with less lumber for the posts and the ridge beam think double not triple. How would that square with building code, roof is 6 in 12 and this is in Texas not much load on asphalt shingle roof.

http://xfloyd.net/images/framing/framing.jpghttp://xfloyd.net/images/framing/house.jpg

[Bruce Breedlove]

Bart,

This is a message board for home inspectors. You should be directing your questions to an architect, structural engineer or qualified framing contractor. I assume you will need a permit to build your addition. Most jurisdictions require an engineer's stamp (a PE - Professional Engineer) on plans for structural work such as this.

[John Arnold]

Well, cathedral ceilings require quite a bit of fertilizer, I believe, and constant weeding. But on the positive side, they don't need a lot of water. In fact, as with most ceilings, it's better if you don't irrigate them at all.
But, I'm just a generalist home inspector, so contact a qualified farmer, is my advice.

[Bart Marek]

Thank you Bruce, I’ve seen similar post on this site, so I figured I’ll post mine. Here in San Antonio Texas obtaining permit is very simple, drawing on a napkin will do just fine J, I guess the only problem is to pass framing and final inspection, that’s all that it’s required, I though someone here might have more specific knowledge about this subject.

[chris mcintyre]

Well, cathedral ceilings require quite a bit of fertilizer, I believe, and constant weeding. But on the positive side, they don't need a lot of water. In fact, as with most ceilings, it's better if you don't irrigate them at all.
But, I'm just a generalist home inspector, so contact a qualified farmer, is my advice.

:D ....:D



Bart,
A couple of things, the lumber yards in my area will size beams as long as you are buying your materials from them, you need to make sure you have this right because, in this case, the ridge beam is the only thing keeping the walls from spreading and the roof from sagging.
Also 2x10's will not work for R-30 insulation. R-30 batts are 9-1/2" thick and nominal 2x10's are between 9-1/4" and 9-1/2", typically.

[Bart Marek]

Thanks Chris,
If 2x10 will be not enough, then I'm thinking of this solution:

Plywood Gusset Build-Downhttp://files.servicemagic.com/files/editorial/images/cath2-2.gif

Figure 2. Hanging 2x3s below the rafters using plywood gussets, the author creates as wide a space as he wants for blown cellulose. The insulation also fills the space between the main rafter and the build-down, blocking heat conduction through the rafters.</B>
As usual, we staple vent channel to the underside of the sheathing. After installing a reinforced poly vapor barrier and strapping across the ceiling, we fill the cavity with dense-blown cellulose.


Read more: http://www.servicemagic.com/article.show.Energy-Efficient-Cathedral-Ceilings.13867.html#ixzz0ouJjnT8u (http://www.servicemagic.com/article.show.Energy-Efficient-Cathedral-Ceilings.13867.html#ixzz0ouJjnT8u)

[John Kogel]

It looks like your planned addition is about 12 X 14' . I am not an engineer, but I don't believe the ridge board needs to be tripled in this case. The grade of lumber, the quality of the rafter cuts and the nailing are critical with that design.

Batt insulation will stay in place better than blown-in.

Where I live, building without a permit brings the value down, not up. Get the help of an experienced builder, at least.

[Bart Marek]

Well john, it's 10x17 and I do have a permit for this addition

[Corn Walker]

A couple of things, the lumber yards in my area will size beams as long as you are buying your materials from them, you need to make sure you have this right because, in this case, the ridge beam is the only thing keeping the walls from spreading and the roof from sagging.

I would skip the triple 2x members and get a pair of LVLs. As Chris says, your local supply yard should be able to spec it for you. Some will even provide an engineer stamp.


Also 2x10's will not work for R-30 insulation. R-30 batts are 9-1/2" thick and nominal 2x10's are between 9-1/4" and 9-1/2", typically.

That's why they make R-30C (http://insulation.owenscorning.com/professionals/insulation-products/applications/cathedral-ceilings.aspx). It's an R-30 fiberglass batt with an 8-1/4" thickness. Be certain to use an insulation vent channel (http://www.adoproducts.com/provent.html) in the bays to maintain the ventilation gap.

You should be concerned about where the ridge beam meets your existing sidewall. You're going to want a post there that can help transfer the load all the way down to the footing or let in a header and use a heavy duty hanger such as the Simpson StrongTie HGUS 410 (http://www.strongtie.com/products/connectors/HUS-HHUS-HGUS_SCL.asp) to transfer the load to the existing wall. If connecting to posts, you will want a heavy duty post cap such as the Simpson Strong Tie EPC-44 (http://www.strongtie.com/products/connectors/pc-epc.asp). Again, your local supply yard should be able to help you spec the right hardware.

Is there a footing under that slab? Where are the j-bolts for your sill plates? Pay particular attention to the center spot on the gable ends since you will have a point-load concentrating half of the weight of the roof there.

[Bart Marek]

Grate inside Corn. I was hoping someone will mention that triple 2x12. I will definitely replace it with double lvl. What’s standard LVL width?
That post in the existing sidewall will have to be made out of two pieces one above the double plate and one below, is that ok? Some suggest that it should be continues post. But it will go all the way to the slab and yes there is footing and plenty of concrete and rebar there, so are the J bolts see below:
http://xfloyd.net/images/framing/slab.jpg


Last thing, anyone familiar with this kind of rafter mounting half way on the beam and the other half above it, which would work great for me since the ridge beam could go under the top of the trusses (leaving original roof framing intact) and also would make nice room for ridge vent. Any thoughts here? Thanks a lot for all your feedback

http://www.forestryforum.com/gallery/albums/userpics/10180/Rafters_in_ff.jpg

[Corn Walker]

Grate inside Corn. I was hoping someone will mention that triple 2x12. I will definitely replace it with double lvl. What’s standard LVL width?

1-3/4 which, when bonded together, are equivalent to a 4x member width. Your LVL manufacturer will specify connection requirements for built-up LVL beams.


That post in the existing sidewall will have to be made out of two pieces one above the double plate and one below, is that ok? Some suggest that it should be continues post. But it will go all the way to the slab and yes there is footing and plenty of concrete and rebar there, so are the J bolts see below:

If it is not continuous you will want to use a strap tie such as the StrongTie MSTC-28 (http://www.strongtie.com/products/connectors/HRS-ST-PS-HST-LSTA.asp) to keep it in tension across the break. You'll need one on both sides of the post. I prefer a 4x post over 2-2x posts when supporting an LVL ridge beam. I also prefer balloon framing gable walls - they are much stronger against high wind loading. When sheathing a gable wall that is not balloon framed, make certain the layout avoids any joints falling at the split between top and bottom sections.


Last thing, anyone familiar with this kind of rafter mounting half way on the beam and the other half above it, which would work great for me since the ridge beam could go under the top of the trusses (leaving original roof framing intact) and also would make nice room for ridge vent. Any thoughts here? Thanks a lot for all your feedback.

There are a number of ways you can frame this and still not disturb the original roof. Think of the rafters as being in a fixed position, and only the location of the beam changing. You'll see that you can move the beam up and down with varying effect. As for the method pictured, it can be more work than other methods. I don't know what the uplift resistance requirements are in San Antonio but the method pictured typically requires hurricane ties connecting the rafters to the beam and strapping (e.g. Simpson StrongTie LSTA-21) or gusseting (as seen in your photo) connecting opposing rafters.

As for the venting, you should check with the manufacturer of your ridge vent. See for example the Cor-A-Vent install diagram (http://www.cor-a-vent.com/pdf/Cor-var4.pdf) for a couple of options.

[Bart Marek]

I’ve got some progress and some questions, after little thinking I followed Corn’s suggestion with balloon framing gable wall and now I’m wondering if diagonal bracing is required for that type of construction or rafter will keep it all in place?
http://xfloyd.net/images/framing/framing2.jpg
http://xfloyd.net/images/framing/framing3.jpg

[chris mcintyre]

I’m wondering if diagonal bracing is required for that type of construction


Yes, it needs bracing.



or rafter will keep it all in place?



No.

There are several ways to brace a wall, let in diagonal, metal strapping, but the easiest way is with the sheathing (osb or plywood).

Question: How wide is the window on the far wall in the picture?

[Corn Walker]

Question: How wide is the window on the far wall in the picture?

I was going to ask the same thing. That header looks undersized to me.

Remember, in a cathedral ceiling there are different forces acting on the wall. The structural ridge beam helps carry half of the load and greatly reduce the amount of thrust at the top of the wall. The wall carries the remainder of the load and must also help to resist horizontal thrust.

Also, from experience I've learned to double my rough sill - it's not required structurally but it makes it a lot easier to nail trim.

[Vern Heiler]

I was going to ask the same thing. That header looks undersized to me.

Remember, in a cathedral ceiling there are different forces acting on the wall. The structural ridge beam helps carry half of the load and greatly reduce the amount of thrust at the top of the wall. The wall carries the remainder of the load and must also help to resist horizontal thrust.

Also, from experience I've learned to double my rough sill - it's not required structurally but it makes it a lot easier to nail trim.

It should also be noted that the jacks supporting the header need to be full length, not cut!

[Corn Walker]

It should also be noted that the jacks supporting the header need to be full length, not cut!

Oops, too late. I believe Simpson Strong-Tie makes a header support connector that could fix it.

I've seen this done a number of times, not sure why though. Perhaps there is a belief that the sill is supporting a load and needs to be supported on the ends more than simply toenailing into the jacks?

[Corn Walker]

Are those 2x4's scabbed on to your built-up post at the top intended to prevent the ridge beam from twisting? Is that what the mfr recommended/allows for supporting the beam?

[Bart Marek]

Header is 4' long made out of 2x6 both windows are same width 4 feet. Some plans that I have here call for 6 inch header for that length in the load bearing wall, and so is the current house uses 2x6 for the headers, also this house has jack studs like I did, but I agree Simpson strong-tie would help caring that load.
http://xfloyd.net/images/framing/framing4.jpg

As far as the 2x6 I also had that design on existing plans, Simpson Strong Tie EPC-44 (http://www.strongtie.com/products/connectors/pc-epc.asp) holds only 3 ½ inch from the bottom and no support for twisting on the ridge beam, so I decided to go with that design. Three ½ inch bolts will hold all that together two through the ridge beam and one belowhttp://xfloyd.net/images/framing/framing5.jpg

[John Kogel]

The first order of putting up a wall in my world is to nail on a full sheet of plywood sheathing so it is square and stays square while you build. Did that on my first building job.
Plywood will be nailed to the post top and bottom as well. It will be strong enough if that ridge can't move.
That window frame might be better with a triple header, But I don't know.
I can't judge that from here, (and i aint the engineer, yahoo).
For the sheathing, I'd be using lots of galvanized nails which grip the best and don't rust.

I'd nail the roof sheathing to the ridge as well as to the rafters. That will help keep the rafters from sagging away. Then they can't push the wall out. Much. :)

In my world, there'd be some attractive beams bolted across there, rafter ties.

[Corn Walker]

I'd nail the roof sheathing to the ridge as well as to the rafters. That will help keep the rafters from sagging away. Then they can't push the wall out. Much. :)

That's the principle issue with cathedral ceilings - because the structural ridge beam carries half of the roof load, and when properly sized has a deflection value of 1/720, the biggest remaining problem with thrust at the upper walls is from rafter deflection. Even if it's not necessary from an insulation perspective, it's always a good idea to use 2x10 or 2x12 members when framing a cathedral ceiling to minimize rafter deflection.

[chris mcintyre]

Some plans that I have here call for 6 inch header for that length in the load bearing wall, and so is the current house uses 2x6 for the headers, also this house has jack studs like I did,...



This where AD's advice has merit. While the headers may meet minimum code, spending an extra 7 or 8 dollars to buy 2x10's instead of 2x6's would have given you 2 to 3 times the load capacity for very little cost. I see that the one header is against the top plate, so if it is a hight issue 5 1/2" LVL's would have been better. Just because it is done that way in the existing house does not make it right.

There is a big difference in meeting code and best building practices, another example would be stacking your framing, which means laying out the studs and rafters so they are in line (stacked) with each other, again not a code issue, just not the best building practice.

I'm not sure if I read it here or heard it somewhere else but it is a good quote, a house built to minimum code means that anything less and it would be not be safe to live in.

I'm not trying to beat you up, because you are making an effort to make sure things are done right. I'm sure there is a builder or inspector that would be willing to stop by and advise you for a small fee.

[Corn Walker]

I'm not trying to beat you up, because you are making an effort to make sure things are done right.

I thought oversight was the cat's job? :)

While there are things I would have done differently here, I'm sure we've all seen a lot worse too.

[Ted Menelly]

This is a ten foot wide room with the walls tied together with the outer wall and the abutting to the home. The ridge beam is only ten feet....a double laminate beam ? The rafters pushing out on the walls ??? in a ten foot stretch ???. The window header is fine and not going anywhere. The rafters are not only on the ridge beam but are gusseted together.


Gents. We are getting a little out of control here. This is a large dog house that is not going anywhere. Sheathing is going to wrap everything.

The only thing I would have done with the roof was I would have gone 16 on center, not 24. I hate 24 on center. Unless you are adding 1x3 strapping 16 on center. Drywall screwed to 24 on center is foolish at best especially with the weight of the insulation sitting on it. With all the over kill going on...why 24 on center.

Ridge venting is the only way to go with a cathedral ceiling and framing the roof the way you did was the smartest thing you could have done. Don't blow the insulation in. Bats will not settle as much as blown in and will allow enough space for venting out the ridge

[chris mcintyre]

Gents. We are getting a little out of control here.

Because we have suggested things that are above minimum code?


This is a ten foot wide room with the walls tied together with the outer wall and the abutting to the home. The ridge beam is only ten feet....a double laminate beam ? The rafters pushing out on the walls ??? in a ten foot stretch ???.

It was suggested twice that he have the ridge sized, if he did, and that is what the engineer said was required, I am not qualified to say otherwise.


Sheathing is going to wrap everything.


I can't find where the OP said this, actually he asked if the rafters were sufficient bracing. Should we have said it will be fine, he then puts up foam board insulation and the inspector turns him down?


The window header is fine and not going anywhere.

Minimum code at best.




The only thing I would have done with the roof was I would have gone 16 on center, not 24. I hate 24 on center. Unless you are adding 1x3 strapping 16 on center. Drywall screwed to 24 on center is foolish at best especially with the weight of the insulation sitting on it.

That is above the minimum code, sounds like you are getting a little out of control here :eek: :D .

[Bart Marek]

It's finally done, thanks for all of you commenting, and giving me pointers it was fun.
http://xfloyd.net/images/framing/framing6.jpg

[Rod Butler]

Nice work!