Need advice on altering a roof support - DIY Chatroom

dtbritt · 11-01-2009, 04:39 PM

Good afternoon, all.

I am attempting to convert some currently unusable attic space to a usable work room, but I am concerned that some of my conceived alterations might compromise the stability of the roof. This first one shows how the roof supports are currently in place (the green lines representing the internal support):

The angle of the supports nullifies any hope at having headroom in the proposed room. As such, I was planning on inserting vertical 2x6 beams, bolting the bottom to the floor joists and the tops to the roof joists. I would also bolt the 2x6 in at the point where the new vertical beams intersect the existing angular supports. I'd then add horizontal beams, bolted to the roof joists on either side and at the intersection of the vertical beams and exiting angular supports. With these in place, I'm hoping I can safely cut out the portion of the angular supports which encroach upon the head space. This would yield the following:

Is this a safe approach? Or am I compromising the stability of my roof? Can anyone suggest a better approach?

Thanks in advance!

Dave

GBR in WA · 11-01-2009, 06:02 PM

Is this a safe approach? ------- NO!

Or am I compromising the stability of my roof? ------ YES!

Can anyone suggest a better approach?-------- Contact a local Structural Engineer for the alterations approved by your local Building Department.
Be safe, Gary

stuart45 · 11-01-2009, 07:00 PM

GBR is 100% correct with his advice. They look like factory made Fink trusses which are calculated for the roof. What you are looking for is an Attic truss. You should always take pro advice before cutting any part of your roof structure.

Yoyizit · 11-01-2009, 09:29 PM

Just by looking at it, your second picture looks unsafe, if you don't use bolts.
I think you can make it safe by adding 4 more struts, but to calculate their length and position and making sure they are in compression takes some doing.
Or you could use bolts with plates if some members will be in tension.

You have to understand vectors.
http://www.google.com/search?client=...UTF-8&oe=UTF-8
and
http://www.whrhs.org/faculty_web/dmo...lculations.pdf

Your roof should probably be considered to be a distributed load
http://www.google.com/search?client=...UTF-8&oe=UTF-8