2x6 Rafter question for an Old 1950's Cape Cod

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Forum topic by PaulMD posted 09-15-2015 10:23 PM 763 views 0 times favorited 1 reply Add to Favorites Watch
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1 post in 947 days

09-15-2015 10:23 PM

Ok I am planning out the replacement of the roof on my 1950’s Cape Cod.

I spoke with the local Permits office and ended up as confused as before I started talking to them.

My current roof system has 2×6 rafters (actual 1 7/8” x 5 3/4”) with 1×4 purlins and metal roofing (older rib style w exposed fasteners) with a 7:12 slope/pitch. The metal roofing has been neglected over the years and cannot be saved at this point.

The rafter span is 12’6” (house is 30’ x 25’ with the ridge running the 30’ length ) with a length of 16’ per rafter. The second floor of the house has finished bedrooms with plaster walls/ceilings (approx 1” thick). From what I have seen the roof would be considered a light roof for dead load purposes and based on my location there is a 40 psf snow load.

I am planning on replacing the roof with a composite shingle roof system (5/8” OSB, ice/water, felt and architectural shingles).

Based on the current load span charts modern 2×6 lumber will not be sufficient to support the roof system (i cant seem to find any older span charts that would cover the larger 2×6 rafters that are installed on the house) and I was told by the Permits guy that I could “sister” a second 2×6 to the existing rafters but he would recommend “sistering” a 2×8 to the existing 2×6 rafters”.

Anyone have any idea what the load span of sistering 2 – 2×6 rafters is vs sistering a new 2×8 to the existing 2×6?

I am planning on doing the ‘glue and screw’ type of mating the new rafters to the existing ones I just want to make sure I select the correct size for the new rafters.

Based on what I was told from the permits office I do not need to pull a permit to replace the roof and from the sound of it they didnt really seem to want to be bothered with it lol.

Thanks for any help with this.


1 reply so far

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2597 posts in 947 days

#1 posted 09-15-2015 11:01 PM

paul if you sister a 2×6 to your existing 2×6 you should be fine when they re roofed my house built in the 40”s i only had 2×4 rafters and the never even upgraded and 20 years later the roof has no for the osb go with 1/2 it will cut down on the weight and do all you need thats what all the roofs in my area are done with.dont over think it and spend more than you need its been fine for over 70 years and with these upgrades you should be good for another 70,talk to your roofer and see what he recommends.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

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