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pcroteau 01-13-2013 04:31 PM

Fixing a central crown in the subfloor
I am in the process of replacing parquet flooirng with hardwood. Prior to removing the parquet we had noticed there was a considerable high point(crown) in the middle of the room (3/4" from the corners - room is approx 16'x16') which slops in all directions, but primarily in a perpendicular direction to the floor joists.

After taking a look at the joists from the basement there does ot seem to be any noticable spacing problems between the plywood subfloor and the joists, so I am assuming that over time the floor joists have bowed slightly while the house was initially settling.

That being said, we do not need the floor to be perfectly level, however we would prefer to get the pronounced high point out of the center of the room.

My plan is to raise the subfloor along the center and plane a bit off the floor joists. This may not be simply, but is this a good idea? Are there any other suggestions?

Note that we do not want to add on top of existing subfloor as the flooring will not line up flush with the other rooms.


joecaption 01-13-2013 04:40 PM

I've never seen an old floor crown in the middle, more often the center or outside has settled.
Is there is any sort of a beam running down the middle causing this?
Have you tryed going below the floor and pulling a brick string tight to see if the joist are bowed up?
Hard to tell without being there or at least some pictures, but I'd be concidering removing everything down to the joist and getting them level and flat then working up.

pcroteau 01-13-2013 06:55 PM

Thanks for the reply Joe.

For the beam there is nothing special running down the middle, just normal joists, but I did run a string and the joists do bow up a little.

As you suggest it would be best to remove everything and level from there, would that be more planing the centre high area? shiming the low area, or perhaps a combo of the two?

Thanks again

joecaption 01-13-2013 10:03 PM

Hard to say without being there to look at it. Depending on what's really wrong with it, sistering, and planing down are easyer to do them trying to shim.

BigJim 01-13-2013 10:29 PM

I just had the wildest thought, I really haven't thought this through at all but here goes. Could an engineered beam be placed under the joists with a 2X4 block or whatever at each end for a spacer. Cut a hole in the floor at the joists that are crowned upward, using a good cabinet clamp pull the joist down to remove the crown and secure the joists to the beam.

While thinking more about this, there would have to be blocks sized for each joist as all the pressure would be on the two end joists and could push an upward crown in them. If there was some way to secure the two end joists so they could handle the upward pressure and not move it might work.

Another thought, once the beam was set and secured onto the two end joists, measure each joist from the beam to the bottom of the floor (not the bottom of the joist) and make all the joists the same measurement from the beam. This would spread all the pressure out and maybe work that way. OK maybe I am all wet here and not thinking this through, anyone see a down side to this?

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