How can I remove this high spot to lay a floating engineered floor?

[redhexagonal]

I've been trying to get my 22m chipboard floor (on joists) flat in two rooms and a hallway of the 1st floor, so I can lay a floating click engineered floor. There is one high spot left in the hallway , which is partially over a steel I-beam which i think is why board is bent out of shape. I would need to remove at least 4mm from the height, preferably a bit more, to get the hallway level - it currently has a hump in the middle on the left. Can I just sand or plane the chipboard back 4mm? The only other thing I can think is cutting out a bit of the floor and replacing with 18mm chipboard or plywood.

The high spot is outlined by the blue contours. there is an I beam under the wall in the lower left that protrudes a few inches up across the doorway on the left

 

[big-all]

before you start get a very long strait edge preferably 1m plus 1.8 hopfully and check its all hill and not 2mm hill and 2mm dip over a large area

 

[matlob]

If you can lift the two boards that sit high you may be better removing material from the bottom where it sits on the beam

 

[redhexagonal]

before you start get a very long strait edge preferably 1m plus 1.8 hopfully and check its all hill and not 2mm hill and 2mm dip over a large area

its pretty horrible with a straight edge, the middle is about 8mm above the rest. Part of the reason is that the room to the bottom of the pic is level but the hallway and room to the left slope away to the top slightly. But even so, the hallway has a lump about 4mm above the room to the left. Boards are running left right and there will be a drop of 4mm on the left of the doorway into the room which will be visible at the threshold bar. The hallway kind of slopes up to the doorway fairly evenly then flattens out and drops a bit as it reaches the door.

 

[big-all]

what are you talking ?? say 4mm over 300mm more or less ??
ok electric plane mess mess mess thrown everywhere without brilliant extraction even then dust and carp everywhere
belt sander perfect tool and up to edge but off course again dust dust dust without decent extraction
next level random orbit sander extraction again but far slower so less aggressive and less dust spread

 

[redhexagonal]

what are you talking ?? say 4mm over 300mm more or less ??
ok electric plane mess mess mess thrown everywhere without brilliant extraction even then dust and carp everywhere
belt sander perfect tool and up to edge but off course again dust dust dust without decent extraction
next level random orbit sander extraction again but far slower so less aggressive and less dust spread

Id say i need up to 5mm off an area 500mm by 400mm . I don’t mind about mess so much as destroying the structural integrity of the board?

 

[redhexagonal]

If you can lift the two boards that sit high you may be better removing material from the bottom where it sits on the beam

This is probably the best way, just dreading getting it up as its properly glued on the tongues and joists

 

[big-all]

what sanders or planes do you have accesses to
if both then plane set at 0.4- 0.6 several passes may even look like the alps then you sand the peaks so nearly level but as long as the average surface is at the level you require with even 50% bevel edge digs and hollows over a say 70mm average width you will be fine as the planks above at least 2or 3 touch points at the peak but full support a few inches away

 

[redhexagonal]

what sanders or planes do you have accesses to
if both then plane set at 0.4- 0.6 several passes may even look like the alps then you sand the peaks so nearly level but as long as the average surface is at the level you require with even 50% bevel edge digs and hollows over a say 70mm average width you will be fine as the planks above at least 2or 3 touch points at the peak but full support a few inches away

I only have an orbital sander. Is it safe to take 5mm off 22mm chipboard flooring ?

 

[big-all]

22mm not ideal but ok 4 would be better but not crucial but avoid 6mm iff you can thats approching 30% off the strength

get 60 grit and put most off the weekend to one side
really better iff you can use a belt sander
how wide is the bump

 

[blup]

Take out the flooring affected, replace with 18mm, and make up with underlay.

 

[opps]

I only have an orbital sander. Is it safe to take 5mm off 22mm chipboard flooring ?

Not sure if you mean a (round) random orbital sander or a (rectangular) orbital sander.

A regular orbital sander would take days to remove 5mm.

Even a regular random orbital sander would struggle. I have a 150mm Festool random orbital that has an addition aggressive mode. Using 40 grit paper, I would expect to spend up to about 2.5 hours to sand the high spot, and that is a £550 sander.

I have a 180mm (rotary only) Festool sander, that would take less than an hour, but it is a £650 sander.

I would recommend using a 75mm belt sander with 40 grit belts. 100mm would be better but they are far more expensive. Not all belt sanders will allow you to flush sand. If you use one that doesn't, you can use a sharp chisel to remove the excess near the door architrave.

A planner will be the fastest with regards to stock removal but you need to make sure that you don't hit any screws.

 

[Tigercubrider]

I would lift the floor in affected areas and replace.
If the floor is glued then cut a smaller area out and a plate can be added on the underside as support
you could use thinner material and double it’s thickness underneath, allowing for joists etc. use shims to get it flat

As you’d be replacing the area in question, you can cut a hole big enough to either stick a usb endoscope/ your phone or your head into the hole to check progress.