20x34 Universal Cottage Expansion

[cashcows]

Hi all,

New to the site and forum, thanks for having me. My wife and I are purchasing 10 acres and looking to modify the 20x34 Universal Cottage into a 24x36 design. If that isn't possible, we were thinking of 20x40.

My question is, would a 24x36 or 20x40 design involve significantly more costs? If so, why? I don't know much about structural engineering, but I'm trying to evaluate the additional cost involved in expanding the original designs.

Thank you

[NathanS]

The 20x34 is designed with a beam and two posts for the second floor support that also serve as the U shaped stair case opening.

If you want to leave that the same, going from 20' to 24' wide means you need joists that can span 15 or 16' - 2x12s can do that, but you would want to double check that the deflection is not too great for tile on the second floor.

Going from 34' length to 40' will likely require another post to support the beam, so you would need to be thoughtful on where to put that. If the goal was for a larger living area then you may want to look into a deep LVL that could span (from memory) about 22' instead of the 14'.

Last thing, a lumber yard salesperson might try to talk you into I joists, but those do have some problems where the floor could meet code but still be quite bouncy, even if it costs a little more I would go with LVL + 2x12s.

In my opinion, the increased cost would be linear - the price per square foot would not change much.

[John Raabe]

Thanks and I concur with NathanS' suggestions. TJI does have I-joists that are designed for low deflection, ask at the lumber yard.