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Old 08-21-2011, 05:53 PM   #1
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Raising Ceiling


Hi all. First post, so go easy. I purchased an older home that needs maybe a little more work that what I originally thought. I have remodeled a home before and have a good DIY understanding, but haven't worked on a house this old.

I have a 2 story Salt Box built in 1897. I have an addition on the back built in the late 70s. The second floor's ceiling height is 6'11" in the original part. I have the attic room to raise the ceiling by 15" which would give 8'2" (which would match the addition ceiling height). The roof rafters are 24" o/c rough cut true 2x5. The existing ceiling joists are true 2x4s. The house is located in the north east so snow load should be considered. The roof slope is 10/12. Once raised, the horizonal width would be 4' with sloped drywall on both sides of the room. Both ends of the rafters rest on external balloon framed walls, but one end (because a the stairwell) rests on an interior wall with bearing to the basement.

Because there is evidence of sag in the rafters, I propose to scab on 2x8s to the existing rafters with adhesive and screws(to also give insulation room with vent channel underneath the roof deck which is not there today). I will notch out the bottom of each new 2x8 resting on the top plate of each outside wall. I will tie in 2x8 collar ties/ceiling joists at each rafter at the top 1/3 of each rafter(which will provide my ceiling structure as well). I was also planning to fur the ceiling because the joists are on 24" centers for drywall. Based on the information above, will this be suffcient?

I don't have a picture at this time, but I will get one.

Thanks in advance for any assist.

Saratoga

Last edited by Saratoga; 08-22-2011 at 04:26 AM.
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Old 08-21-2011, 08:45 PM   #2
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Raising Ceiling


Need to consult with an engineer, and the fact that you are making structural changes, your local AHJ will want to see some blueprints from an architect, and the calc's from the engineer.
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Old 08-22-2011, 08:26 AM   #3
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Raising Ceiling


Ceiling joists are often used as "ties" to hold the base of the rafters together during compression loading from snow. Moving of these members without proper consideration of the loads involved could give you bad results. I agree with greg, that while you may be able to perform the physical work, it would be best to get professional advice on how to re-frame without affecting the structural integrity. Especially if we get another winter like the last!
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Old 08-22-2011, 12:09 PM   #4
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Raising Ceiling


Raising the ceiling joist up toward the middle of the rafters puts more pressure on the middle of the rafters where there is the most flex to begin with. If the rafters flex, this will cause the walls to lean outwards out of plumb, the pressure exerted on the rafters could pull a belly in them.

Snow load and you compound the matters that much more. If you can make your rafters and joists trussed that might be a better way to handle that situation. You sure don't want to start cutting ceiling joists without tying the outer walls together as you are really asking for some heavy duty problems that would be very very hard to correct if at all.
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Old 08-27-2011, 06:20 AM   #5
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So the current original collar ties are not on top of the wall. They are 4'4'' up the 10' roof rafter. You can see each side of the tie in the pictures. The east wall accomodates a stairwell with a small kneewall. The collar tie does not rest on that wall either.

You can also see new 2x8 rafters resting on the outside walls and matched at the ridge. In the third picture you can see where I propose to place the 2x8 collar tie (at 6' up the 10' rafter). This would give me a 4' horizontal run for the cieling with the sloped roof section on either side. Using wider lumber(vs 2x4) for the collar tie it provides some axial strength because it is at the top 1/3 position on the rafter.
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Raising Ceiling-collar-tie-east-side.jpg   Raising Ceiling-collar-tie-west-side.jpg   Raising Ceiling-new-collar-tie-location.jpg  
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Old 08-27-2011, 07:08 AM   #6
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Do your rafters sit on the upper plate or on top of the ceiling joist on your house? A large number of the old homes built in the early 1800's were with the rafters sitting on top of the ceiling joists which were cantilevered out over the top beam. If the ceiling joists were cut on one of the older homes the rafters would push the ends of the ceiling joists down and fall.

The ceiling joists were notched to sit over the top plate or beam, in the older homes. The notched ceiling joists held the walls in place as the old tapered iron nails didn't have much holding power at all. A lot of the older homes were post and beam construction.
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Last edited by BigJim; 08-27-2011 at 07:11 AM.
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Old 08-27-2011, 07:24 AM   #7
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The roof rafters are notched and rest on the top plates while hanging over for the soffits.

Last edited by Saratoga; 08-28-2011 at 06:58 AM.
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Old 08-27-2011, 08:31 PM   #8
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The problem is interior loading of the existing under-sized rafters with wall and ceiling drywall. The collar ties could be moved up (3/4 the page down); http://myconco.com/ComEngProb.html

The rafters need to be strengthened to clear-span from plate to ridge unless the knee-wall has bearing below it. Sistering the rafters from knee-wall to ridge puts the added interior load (and existing roof/snow load) all on the knee wall.



1. Is the knee wall a bearing wall?


2. What size/span of rafters?



3. What size/species/span of ceiling joists now converted to storage/living space?


You need a permit for this structural change under the 2009 IRC; http://docs.google.com/viewer?a=v&q=...1txlzU01V4JQIg


http://publicecodes.citation.com/ico...002_par017.htm


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Old 08-27-2011, 08:44 PM   #9
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Quote:
Originally Posted by Saratoga View Post
So the current original collar ties are not on top of the wall. They are 4'4'' up the 10' roof rafter. You can see each side of the tie in the pictures. The east wall accomodates a stairwell with a small kneewall. The collar tie does not rest on that wall either.

You can also see new 2x8 rafters resting on the outside walls and matched at the ridge. In the third picture you can see where I propose to place the 2x8 collar tie (at 6' up the 10' rafter). This would give me a 4' horizontal run for the cieling with the sloped roof section on either side. Using wider lumber(vs 2x4) for the collar tie it provides some axial strength because it is at the top 1/3 position on the rafter.
Are you getting permits and inspections?
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Old 08-28-2011, 07:29 AM   #10
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Raising Ceiling


The rafters need to be strengthened to clear-span from plate to ridge unless the knee-wall has bearing below it. Sistering the rafters from knee-wall to ridge puts the added interior load (and existing roof/snow load) all on the knee wall.

This room was present in the original house with low ceilings and two layers of plaster and lathe.



1. Is the knee wall a bearing wall? The knee wall rests on a double microlam with bearing to the basement.


2. What size/span of rafters? The orginal rafters are rough cut true 2" x 5". I have a sister 2x8 beside each that rest on the top plate of the exterior walls. Length is 10' and horiz span is 6'10" per rafter with no ridge beam. 13'9" room width.



3. What size/species/span of ceiling joists now converted to storage/living space? 11' horiz span. rough cut 2 1/2" x 5" 110yr old what looks like pine or fir.

Last edited by Saratoga; 08-28-2011 at 07:48 AM.
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Old 08-28-2011, 07:38 AM   #11
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Quote:
Originally Posted by Saratoga View Post
The rafters need to be strengthened to clear-span from plate to ridge unless the knee-wall has bearing below it. Sistering the rafters from knee-wall to ridge puts the added interior load (and existing roof/snow load) all on the knee wall.

This room was present in the original house with low ceilings and two layers of plaster and lathe.



1. Is the knee wall a bearing wall? The knee wall rests on a double microlam with bearing to the basement.


2. What size/span of rafters? The orginal rafters are rough cut true 2" x 5". I have a sister 2x8 beside each that rest on the top plate of the exterior walls. Span is 10'.



3. What size/species/span of ceiling joists now converted to storage/living space? 11' horiz span. rough cut 2 1/2" x 5" 110yr old what looks like pine or fir.
Are you getting permits and inspections?
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Old 08-28-2011, 08:36 AM   #12
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Thanks for the reply, Joe. I have not yet applied for a building permit.
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Old 08-30-2011, 03:40 PM   #13
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Your Inspector will tell you if the spans/loads are acceptable for the old-growth timbers with the knee walls taking most of the new loads in finishing. Moving the collar ties up isn't as critical as roof bearing paths to the earth. Also remember new codes require proper sized floor joists for storage or living space, egress window or door for attic rooms, an egress stair and hallway, etc..... to keep everyone safe in case of fire. Nice paper trail for your H.O. Insurance carrier for future claims, non-negotiable point at selling time also.

Gary
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