Subfloor Sagging

[Ernesto]

Had a demo crew out to rip out a tile job upstairs for my Hallmark job coming up. The tile looked like the surf coming in. I told the lady/owner something is messed up besides the krappy tile job the unlicensed hacks did. Tiles busting loose, grout cracking out, flatness off by 2 1/2 inches in spots.

She had some engineer out, he looks at the ceiling down below and says...no structual issues up there, it is just the tile.

So the demo guy calls up and says we need a meeting. The subfloor and joists are sagging in some areas and he wants to brace it and add some 3/4 ply, but also leave some old OSB to go over top of.

Question is, how can the floor sag but look perfectly fine underneath? I think there must be a couple feet of airspace between the two.

This is going to be interesting. Taking camera for this one.

 

[Ken]

Drywall can be wrapped around all sorts of curved surfaces, especially if its 3/8 thick. If he didnt put a straight edge on the ceiling how the heck did he know that the joists werent all over the place? A subfloor can "look" flat until you lay a straight edge down.

 

[Floorist]

Probably a "drive by" inspection.

 

[DarisMulkin]

I can give you an educated guess. When they did the ceiling down below some snapped a chalk line from wall to wall a cut the curve out off the joist. How do I know that you ask? I did it on a house that I owned that was about 110 years old. I numbered the pieces and put them back on top of the floor joists in the upstairs at a later date to level the floor.

Daris

 

[Ernesto]

I can give you an educated guess. When they did the ceiling down below some snapped a chalk line from wall to wall a cut the curve out off the joist. How do I know that you ask? I did it on a house that I owned that was about 110 years old. I numbered the pieces and put them back on top of the floor joists in the upstairs at a later date to level the floor.

Daris

Why the hell would you intentially jack the floor joists up?

 

[DarisMulkin]

Made it flat. With no problems, the house is still standing almost 40 years later. Got to figure they weren't 2" material, more like 3x 9. Besides I only took out about 1/2 in the middle.

Daris

 

[Ernesto]

OK I get it now.