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Community and Q&A

Hip roof modifications

Miriam Kearney | Posted in GBA Pro Help on

I I have just purchased a small house (20 x 24) with a hip roof in Zone 5A. The house has been extended but each (of 2) additions has its own roof. My question is about the hip roof.

The house is about between 75 and 100 years old. The rafters appear to be 2×4 (old size, not dimensional size), there are knee walls about 4 feet from the 24′ edge and a tall wall at one end about 5 feet at the same point one one end and a dormer at the other. The dormer is framed to the floor so it is effectively the same as the other end. There is also a cross bracing going on at about the 5 foot level between the two sides that have the knee walls.

My 1st question is – if I replaced or added to the common rafters with a 2×6 dimenstional could I remove the knee and/or tall walls and/or the cross bracing?

I would like to make this area into living space for a bedroom (albeit a small one) and anything I can remove would make it visually if not practically larger. The knee walls are on the 24′ length walls and the dormer and taller wall are on the 20′ dimension. If I cannot remove the knee walls can I reframe them (like cutting a window into load bearing wall) to insert short dressers along the length ?

I am removing the existing insulation (above the cross bracing and behind the knee walls), replacing with closed cell spray in foam between the rafters. Sistering the 2×4 rafters would let me put more insulation in if needed. My insulation contractor says he can put R18 in the 2×4 rafter bays.

Thanks for your help.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    Briefly, modifications to your roof are possible, but you'll need to hire an engineer to advise you. There are two many variables for us to provide engineering advice from your description.

    It's probable that your existing 2x4 rafters will have to be beefed up in some way before you can begin renovating your attic.

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