This is yet another sistering question.

 I’m in the process of fixing the 24′ x 24′ loft in our pole barn. It has the following issues.

1.            Posts are not anchored and appear to be too small (4×4)

2.            Hangers appear to be undersized for the 2×8 joists

3.            There is a 1″+ sag in the center

4.            There is no guardrail (plus there is a 24″ gap in the floor – apparently the previous owner ran out of subfloor material)

These are the corrective steps I’m planning:

1.            Level the floor and add sisters

2.            Install new PT 6×6 posts

3.            Frame joists for the 24″ gap mentioned in #4 above. I also plan to add a couple of additional posts below this area to support lumber storage in the loft.

4.            Add a guardrail.

Here are my questions:

1.            Since the existing joists are supported by hangers, can I add angle ties as reinforcement?

2.            Do I need to run the sisters the full length of the joists? The existing joists are sound – no rot or damage.

 
Obviously I’m trying to avoid tearing out the old hangers if at all possible.

The green parts in the attached jpgs are new lumber. The existing posts to be replaced are red.

Thanks!