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juststarted 11-10-2011 10:17 AM

Another 2x6 cathedral ceiling
So I have done plenty of research on this topic and haven't found all the answers I need. The usual disclaimer: I am not a builder by trade and do not know all the correct terms. I bought a single story ranch last year. There is a bonus room that is built on a slab. This room had a half cathedral ceiling with very strong mold smells. Tore the room down to studs to find foam board insulation just pressed against the underside of the roof with mold from lack of air flow. I would like to put this room back together with a full cathedral ceiling. The rafters are 2x6 and there are no collar ties and just a few 2x4's as joists in the area that wasn't cathedral. It is a smaller room (15x11 ish). The peak runs in the long direction of the room, and the rafters are angle cut and set on top of the walls (common rafter construction).

I am on a very tight budget here and this home is not a forever home so it doesn't have to be the best insulation job with an R5000 value like I see some people trying to achieve.

Foam insulation, I am guessing, is out of the question due to cost.

I can either furr out the 2x6's or sister them. What I am unsure of is where the wall line meets the ceiling line. The only options I see is to either shorten the wall by carrying the new ceiling line down at the same angle as original, or taper the new rafters in at the bottom creating 2 different angles as you go up the ceiling line.

I am not trying to meet a specific code R-value, just trying to make the room comfortable to live in and as an added bonus.. mold free.

I have also read some comments of doing a partial cathedral ceiling, where you leave the 2x6's and insulate accordingly. Then in the flat area of the ceiling, insulate more. This method assuming the angled portion of the ceiling acts more like the walls in heat loss and the flat portion the true ceiling area. Not sure how much I buy this.

Thoughts? Opinions?

I know it would be best to bring in an engineer ect ect but that is not an option here. I already plan on making the room stronger by adding collar ties that arenít there. The room has been standing many years without sagging so I am not too worried about any issues with that.

CaptainD51 11-10-2011 10:49 AM

I'm assuming you want to sister 2x6's to make a straight ceiling line which should be fine. My question would be what are your plans for ventilation so you don't get mold ?

sixeightten 11-10-2011 10:50 AM

Flat ceiling with fiberglass insulation. Check for roof venting issues as well. Some pics can help us be more specific.

juststarted 11-10-2011 10:55 AM

That seems like the easiest cleanest option, but lowers the point on my walls where the ceiling would hit the wall. I am thinking this might give the room an odd "smaller" feeling, but I don't know. I have also seen this done where there was a small few inches of flat that came out of the wall and then the ceiling continued up at the correct angle... This also seems weird to me as well as a lot of work.

As far as venting, I plan on installing soffit vents and a ridge vent. Leaving approx an inch between the insulation and the underside of the roof for air flow.

dougp23 11-10-2011 02:23 PM

As someone who just shelled out a lot of money for mold remediation in the attic, here would be my advice:

Consult a roofer.
You would probably want proper vents between that foam and the sheathing.

But def consult a roofer! My two cents.

juststarted 11-10-2011 02:32 PM

Thanks for the replies so far!

The obvious easy solution is a flat ceiling, but I am trying to keep the cathedral.

I actually had a roofer that was going to come by last night but got tied up. I am just trying to get some info on my own as well.

The foam pushed right up against the sheathing was the previous construction. That is what caused the mold and has all been removed and will not be put back that way. I am planning on space for ventilation between the insulation and sheathing.

sixeightten 11-10-2011 02:57 PM

How about a flat soffit off the top of the wall at the bottom. You could extend this in about a foot or so and then furr down the 2x6 rafters from there. This way you can insulate, but maintain the lowest part of the room at the current height.

sixeightten 11-10-2011 03:05 PM

1 Attachment(s)
Like this maybe?

juststarted 11-10-2011 03:13 PM

You are right, I forgot to mention that option. I have seen that before and it didn't look too bad. When I get home tonight I will take some pictures and some measurements to get a better idea of how much overhang would result in doing the flat section like that.

My fear would be ending up with the flat section looking all wavy as it goes down the room.

sixeightten 11-10-2011 03:32 PM

Shouldn't be wavy. Run all framing to a string, and when you put the drywall bead on, just visually check to make sure it looks straight.

juststarted 11-10-2011 08:29 PM

4 Attachment(s)
So here are some pictures. You can see the 2 2x4's that are the only acting support at this time. The area to one side is what use to be the roof of the house (now with a hole cut into it to connect what airspace there was to the attic. This did nothing for actual venting.). I will likely end up going straight up that side of the room.

I did some quick math after I took some measurements. I have about a 30* roof... this means if I went to 2x10's I would either have 8" of flat "soffit" area that came out into the room, or I would have to come down 4.5" on the wall. Currently the wall is already kind of short at 6'10" and there is 10" between the highest window and the point of intersection with the ceiling. That means the wall would end up 6'5" and I would only have about 3" between the top of the molding around the window and the point of intersection.

I am not very good at visualizing these things and am not sure which would be more odd to walk in and see...

The last option I am looking at is leaving the 2x6's as is and insulating (leaving vent room obviously). Then going over the whole thing with foam board. I could then screw strapping right to the foam into the joists and drywall on that. Instead of 4" of thickness added I would only have 1 or 2. Making either the over hang or loss of wall height much smaller.

I haven't crunched R values on that or costs yet, but its just a thought.

Gary in WA 11-11-2011 08:09 PM

It appears from the pictures you have a ridge board, not ridge beam, big difference:

The collar ties only tie the rafters together at the peak, same as gussets. You need rafter ties, 2x's running with the rafters at ceiling level, sized to carry the drywall ceiling. The missing ceiling joists/rafter ties should be replaced to keep your exterior walls in-line, from bowing out. This is structural and important.


juststarted 11-21-2011 09:54 AM

Yes you are right it is a ridge board not a beam. This room was never constructed correctly from the beginning and I am working on correcting it without tearing it down. I checked all the walls and the board for sagging and only one wall is pushing out a bit (shocking). I am going to correct this and am installing rafter ties around the 1/3rd height. This will give me a semi flat ceiling but that is ok.

As added support I would like to put in some 4X's tying the two walls together and leaving them exposed. It is about a 15' span from wall to wall. Question is how should I connect them to the top plate? I would like to through bolt them but wasn't sure if this would weakened the top plate by having a hole drilled through it. I am also thinking 4x6's. I would rather a 4x8 but there is limited room between the top plate and the sheathing. Cutting a large amount off the ends of the beam doesn't make much sense.

Gary in WA 11-21-2011 04:35 PM

This is when you hear "contact an Engineer" for the fasteners attachment, from me.....
Give you any idea;


AndyGump 11-21-2011 06:58 PM

Where are you located?

There may be prescriptive (code based) framing procedures that you can use to make this comply with your local codes.
Then you can have it inspected and be legitimate.
As I always try to say, you will need a set of plans to take to the BD and get the O.K. from them to proceed.


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