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Old 12-28-2015, 09:07 PM   #1
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Attic conversion


I am starting a conversion of my storage attic into a 4th bedroom. The house was built in '42 and it has stick built 2x6 rafters with 2x4 framed support wall under the rafters. I have 5 rafters on one end of the attic that are not in line with the other rafters. They are about 1" lower then the others. I was going to just plane the bow out of the low rafters to even them up, but after checking how much I would need to remove, I noticed that I would have to rip 1" off the full length of the rafters. Which would mess up where the drywall would land on on the peak. Now I was thinking I would just sister 2x4s to the rafters and come down about a inch to have a good straight run to hang drywall. My question is whether doing it with 2x4 would still provide the support for the roof. Here is some pictures of what I'm talking about.
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Old 12-28-2015, 09:30 PM   #2
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The notches are the show how much u need to remove
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Attic conversion-bdbb15dd-1e58-4189-987d-9f2482fe2794_1451358953875.png   Attic conversion-p_20151228_135527-918x1632_1451359701051.jpg   Attic conversion-p_20151228_135555-918x1632_1451359722117.jpg   Attic conversion-p_20151228_135641-918x1632_1451359734778.jpg   Attic conversion-p_20151228_135626-918x1632_1451359752184.jpg  

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Old 12-29-2015, 03:20 AM   #3
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Converting an attic space to a bedroom can be involve other issues, egress, minimum insulation, AFCI protected wiring, roof/attic ventilation, and in your case, perhaps jacking up those rafters instead of locking then into a lower position.

Also, the kneewalls will be transferring the load from above to the ceiling joists below, that may need to be addressed. Get your permit and discuss all issues with your local code authority, they are your source.

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Old 12-29-2015, 04:00 PM   #4
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The attic floor joists may also need to be upsized to meet current code. There is a difference between limited storage in an attic vs a bedroom.
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Old 12-29-2015, 04:21 PM   #5
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I've checked code and the attic meets the reqs to convert. 2 windows and the floor joists are 2x8s
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Old 12-29-2015, 04:43 PM   #6
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Whats the span of the 2x8 and in my area you need 5.7 cubic feet clear span on 2nd story window when its open
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Old 12-29-2015, 06:23 PM   #7
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From what I can measure its 32' inside to inside of the attic space. I believe one of the walls on the first floor is load bearing and it is 13' from the outside wall. But it doesn't go the full width of the house. Not sure on the other walls. Its crawlspace on those sections. The one wall I think is load bearing lines up with the basement wall.
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Old 12-29-2015, 06:42 PM   #8
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Attic conversions by newbies tends to result in poor non-compliant conversions that have limited viability or enhanced property value.
Beyond that there are a lot of important issues to address. First off STOP notching your rafters or don't let anyone else do it.
Secondly load rating on your floor joists is the big issue. It is highly unlikely that your 2x8 joists will load calc out to a 19' span. 32' width minus 13' wall on 1st floor presumes 19' span in at least part of the attic.
Natural light and ventilation requirements, along with heating, electrical and insulation would need to be met under a compliant conversion. If actually get a Municipal permit for this conversion your stairs leading to the attic will need to be compliant as well. Chances are in that age house risers are too high and treads too narrow.
Its your house, you can do whatever you want. If you plan on staying there for a long time what you do probably won't matter. If you are looking at increasing your resale value a bad conversion probably won't help you much. I write up illegal non-compliant conversions regularly. Owners are always horrified at their failures. Buyers are grateful they didn't end up buying a DIY POS.
Do your homework and get it right. You may not like it now but you'll be better off for it later.
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Old 12-29-2015, 08:20 PM   #9
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Makes more sense to shim the skinny rafters than to trim the fat ones.
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Old 12-29-2015, 08:57 PM   #10
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The plan is to sister 2x4s to the rafters and connect the support wall to the 2x4. My question was whether this will still be structurally sound
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Old 12-29-2015, 09:16 PM   #11
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One of the problems with sistering the 2x4 to a rafter is the irregular space it creates in regards to proper insulation. Besides the additional thermal bridging it will be difficult to fit the insulation in neatly.

Are you planning to vent above the insulation from soffit to ridge vent? What is the minimum insulation level for your climate?

If you need more space to accommodate the insulation and the ventilation, this would be the right time to add that 2x? directly below the existing rafter, trimmed to yield a level surface on the inside.

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Old 12-29-2015, 11:49 PM   #12
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There is no soffit or ridge vent. Just the gable end vents. I was told since the roof has 5 layers there wouldn't be much issue with condensation. If need be I can put a moisture barrier between insulation and roof. I went with r19 because the floor has blown insulation, so all I'm insulating is the attic space. I figured I would be able to trim the inch and a half off the roll insulation to account for the added 2x. I was going to have to do that anyway because the space between rafters was irregular.
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Old 12-30-2015, 07:37 AM   #13
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It sounds like you are headed in the wrong direction. 5 layers above, unless they add up to r-40 insulation, are not going to stop the condensation. It is the moisture from inside seeping into that assembly that will form the condensation and rot that roof.
Search "GBA venting a cathedral ceiling" and read Musing of An Energy Nerd by Martin Holladay.

To meet code you also need more than r-19, plus soffit to ridge ventilation.

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Old 12-30-2015, 07:39 AM   #14
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Roof has five layers? The weight load on that rafter system is probably at or above the design limits, especially if you live where it snows.

It's your house but it doesn't sound like you have enough room for the attic insulation. Insulating an attic room is tough. The heat load from the roof is very high.
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Old 12-30-2015, 10:52 AM   #15
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If the roof has 5 layers, then you have most likely exceeded load limits. Maximum 3 layers is common under municipal code requirements. As far as whether your rafter sistering scheme will work is suspect. With mid span knee walls it will probably be fine, if you keep notching the rafters you'll probably be screwed. Depending on how you plan to attach the 2x4's you could cause splitting in the 2x6's which would weaken them. Beyond that you don't list your location so we have no idea if there are snow loads in your area.
I suggest you consider removing roof layers first and then doing the attic conversion. A better option is to attach 1x's to the roof rafters perpendicular and then shim them in/out so that you end up with a nice flat plane. Easy install if you get the knack of it.
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