finishing an attic - DIY Chatroom

jcsullivan · 11-03-2009, 07:06 PM

I am looking to finish my attic for a rec room, the house is a two story colonial. The existing floor joists are lapped and the rafters are offsett - they didn't use one joist for the 28' width of the house. The existing floor joists are not strong enough to carry the load so I will need to put in sister joists. My concern is the sister joists may/will not be directly above the studs on the floor below and will be resting on the top plate of the wall below. Is that acceptable? Note, I would prefer to use I joists so I will not need to lap the sister joists and they are much lighter.

CustomBuild · 11-04-2009, 12:27 AM

A double top plate is considered load bearing. This is why it is ok to put rafters 24" OC on top of a 16" OC framed wall. So be sure to verify that you have a double top plate. As far as using TJI's read the literature that comes with them. There is a lot of good info regarding penetrations and fastening methods. Hope this helps.

GBR in WA · 11-04-2009, 12:52 AM

I suggest you clear this with your local Building Department. You will want the added habitable space on your County's permanent record, so you don't have to permit it later at selling time. Your homeowners insurance will need to be notified as well to cover you for mishaps.
The B.D.'s are their to ensure you build to minimum code for safety, both structurally and fire-safe. The stairway going up has minimum requirements, the windows (for light and ventilation- possibly egress), heating and cooling units, and electrical may need up-grading, rafter thickness for insulation, smoke detectors, etc. The studs in the first floor of your now 3 story need to be 2x6, 16"o.c., not 2x4's.
Be safe, Gary