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Re-Supporting Kitchen Roof / Ceiling

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Jun 24, 2014, 04:27 PM
Re-Supporting Kitchen Roof / Ceiling

House Built: 1915
Room Span for supports: About 14-15 ft (wall to wall)

Hi All,

So I just had my flat (slightly pitched) first floor roof replaced which so happens to be over my kitchen (both were extensions onto the original house) Nothing above the roof.

So with that I decided to replace my kitchen ceiling as well. I had the usual drop ceiling grid with the lath/plaster. So I got rid of all that and am now down to the wood supports.

The joist structure is a two tier structure with one tier (top tier) of 2x8 supporting the roof which sit on the shoulder plates of the kitchen structure and the other tier (lower tier) is made of 2x6 joists which support the ceiling. They sit on (or rather are etched into) 1x2's which are nailed into the shoulder plates

Now I have two problems:

1). The tip tier joists sit about 24" apart on center. Not sure if this is a typical setup. The middle joist cracked straight in half (probably from the winter snow weight). In order to get the roof replaced the roofer simply resupported the cracked joist with 2x8 pieces so they could apply the plywood board, but now I need to either sister this middle joist or add 2 new 2x8 joists (one on either side of it) to properly support the middle load.

Any ideas on the best course of action for this is appreciated?

2). My lower tier joist support system for the ceiling is sitting on 1x2's. Quite flimsy for my taste and they wobble like crazy. Yes they have been like this since the kitchen was built some 50 years ago and yes my new ceiling will be lighter then the old one, but now that I have it open I want to resupport them and get rid of the side to side wobble and slight vertical wobble.

Any idea how I should go about doing this?

Thanks all for any ideas you may have for me.

P.S. In case anyone is wondering about new ceiling weight I plan on putting some 6" recessed lighting around the room perimeter and a ceiling fan in the middle.
Jun 24, 2014, 08:46 PM
First the bad news: The roof structure is built way too lightly. 2x8's set 24" OC over a 15' span are going to fail eventually. Judging by your broken rafter from last winters snow load, that eventually may be fairly soon. At a minimum you need 2x10's set 16" OC. This is even more important considering that it's an almost flat room and you live in a snow area.

Before you close things up, I would add a new rafter in-between each one that is currently there. Even if you can only fit in 2x8, this would put your framing at 12" OC. If yuo can manage to fit in some 2x10 and/or sister 2x10 to the 2x8 then even better.

For the ceiling framing you can add solid blocking between the joists along the walls above the 1x2. You can also add solid blocking staggered along a centerline of the joists - this will really stiffen things up. You can also brace the ceiling joists to the roof rafters if not already so each span set of framing can help support the other.

Jun 24, 2014, 10:35 PM
Hi Jaybee

Thanks a lot for the informative post.

Couple of questions for you

#1 for the sistering and/or adding new joists between the rafter joists. Should I get stock lumber from the big box stores or should i have them special built? I ask because i have heard that when the lumber is custom built for you they do not have the arch that the stock lumber from the stores might have which may cause an unevenness to the finish.

#2 - When you say add blocks above the 1x2. Can you possibly give me some demensions? Are we talking 2x4?
As for the staggered blocking along the center, should I use the wood bridging or should I use metal braces to bridge? I recently seem them in use on a new structure and i heard they work quite nicely.

Please see the below links I took three pictures of my issues:

Pic #1 is of the 2x6 resting on the 1x2.
Pic #2 shows the 2x8 rafters plus 2x6 joists below. Both without any bridging
Pic #3 shows the broken 2x8 rafter from underneath. The roofers adding some wood to keep it together so they could put in the plywood underlayment.
Jun 24, 2014, 10:53 PM
all lumber has a "crown." part of the trick is to pick your own lumber, sight down the board, and reject anything with a noticeable crown. be a good shopper and put the other wood back on the pile. you can also lay the lumber flat on the floor. a rocking piece, uh-uh. do this on opposite sides, since no concrete floor is really flat over any distance.

nobody "custom builds" framing lumber. even if they plane it, the grain structure that leads to crowning is still there, and it will tend to warp again when put up.

when sistering, use plenty of construction adhesive between the boards. you probably want to pick up an exterior grade, since the roof is in a cold zone, meaning whatever the weather is outside, it's supposed to be like that above the living area. screws are great, nails work too when there is enough construction adhesive. I suspect since it's in a cold zone, that ceramic coated deck screws would be preferred.

sig: if this is a new economy, how come they still want my old-fashioned money?
Jun 25, 2014, 08:54 AM
I'll second what swschrad said - There is no 'custom' framing materials other than engineered trusses or paralam beams. The best thing is to sight each board for straightness and pick out the best. That's why at most supply places, you'll see a bunch of wood piled up on the back of the stack with nice, neat wood in front. The stuff in the back has been picked through and rejected.

On the pics:

1. Really nothing wrong with the 1x2 ledger set-up. It's an older style of construction that has be replaced by metal joist hangers but the rafters are still supported.

2. Blocking is best if the same stock as the rafter or joist you are blocking to. Don't bother with the metal strap cross blocking in your case - to work correctly the strapping has to be installed across the top and bottom of the rafter - an option you do not have since the roof decking is already in place. I say to use a staggered line of solid blocking because it's the easiest way to install it. Snap a line along centerline of the span, then install one block to the left of center and then next to thee right of center. This way you can securely attach each block without toe-nailing.

3. That 'fix' to the split rafter is doing next to nothing. At the very least it needs a full-length rafter of the same size sistered to the existing broken one.

3A - If that's the kind of work done by someone you have hired then it's time to get another guy who knows what's he's doing.

Jun 25, 2014, 01:01 PM
Hi Jaybee/swschrad,

Thanks so my followup question:

The split middle rafter in pic #3, the roofer nailed the temp wood into it so I couldnt easily remove it to add the sister joists without further damaging the split joist.

I was wondering, would it be ok if I built out the split joist with more 2x8 pieces so I could then properly add a sister joists next to it?
Jun 25, 2014, 09:06 PM
As long as somewhere in there you have a full run 2x8 that take the load off of the broken rafter. The closer you can attach it to the rafter the better but it will also work well to add one to the space on either side of the broken rafter.

Jun 25, 2014, 09:48 PM
Thanks jayBee,

I think my plan is going to be to sandwich the broken rafter with two new full run 2x8's. I think that should give the middle some heft to handle a snowy winter Smile