SISTERING JOISTs or LVLs 1

[MIB4X4]

I am helping a friend who is wanting to add a room in his attic. The current joists are 2x8x16 - 16" OC.

He is wanting to add a set of stairs from the second floor to the attic. The stairs are to code but i told him that his fastening points look questionable.
The room underneath is a bedroom with no supporting stanchions. The room dimensions are 15x15, with 8 foot ceilings. He cannot put 2x10s in due to height restrictions.

The questions is should he use 3.5 x 7.25 LSL in the framing for the stairs and floor support, per attached schematic, or what is the best recommended proceedure to make sure the ceiling will support the weight of a bedroom?

Attached is a homemade schematic. (Dont laugh ;-) )

Thanks in advance.
- Mike

 

[sundale]

"...what is the best recommended proceedure to make sure the ceiling will support the weight of a bedroom?

Answer: Hire a licensed professional structural engineer to review the proposed modifications to the existing structure.

 

[ztengguy]

I would go with the 3-2x8's if they work. Should be cheaper.
Have you checked deflection for the sistered joists? how do you plan to get them into the attic and into place?
Check the point loads too on the load bearing walls.

 

[MIB4X4]

ztengguy - Thanks for the reply. There are two windows installed in the gables of his attic so that is how he will get them up there. Do 3-2x8s sistered offer the same strength as 3.5x7.25 LSL?

 

[allcad1]

Hello all,

From the sketch I am wondering about headroom at the top of the stairs. Do you have a rough sketch of section through the attic?

Joseph

 

[ztengguy]

MIB4x4, I cant answer that, without knowing all the properties, and to reference Sundales post, I am not going to provide free engineering. Spend $500 and hire a local engineer.

 

[RHTPE]

sundale & ztengguy have it right.

LVL's have advantages over sawn lumber. Higher E & Fb. Straighter than sawn. Sawn lumber will shrink substantially as it dries to equilibrium MC, LVL nowhere near as much.

As far as size & number, see first sentence.

Ralph
Structures Consulting
Northeast USA

 

[wannabeSE]

Is this space already an occupied room, or are you converting an attic into a room? 15' is a long span for 2x8 floor joist. Have you checked the deflection of the typical floor joist. I think a local structural engineer may be needed.