Vinyl plank - Basement concrete - Level question

[satishtiru]

I am doing Basement Concrete Subfloor - Rigid Vinyl plank installation. Lifeproof vinyl plank installation instructions has "Be level to within 1/4 in. in a 10 ft. span; slope 1 in. in 6 ft.;"

What does this mean by "Be level to within 1/4 in. in a 10 ft. span"?
In a 10ft circle from one end to another, if I put a laser level, difference should not be more than 1/4 inch. Is this correct?

I have 72 inch straight edge level and laser level to check.
Thank you for your help.

 

[C.J.]

The term should be flat as opposed to level. If you have a 6’ straight edge, or level, you will place it on the ground and look at how flat the floor is in relation to the straight edge.

You will slide the straight edge all around the basement and mark any high spots to be ground down or low spots to be filled in

 

[Commercial Floor Rep]

If you're using a 6' straight edge then you generally reduce the tolerance to 1/8" in 6'.

 

[satishtiru]

More information request:

For example, I have an alley facing north with 6 foot x 16 foot (alley size). Half of this space (6x8) is flat compared to other half.
Whole space is flat if I put 6 foot level parallel to North facing wall and move from one end to another end with 1 foot increments. But when i put 6 foot level parallel to east facing wall, half of the room is flat and but the other half is not flat compared to first half. In this scenario, how should I fix the floor levelling? I'll be laying vinyl planks going east - west (parallel to North).

It seems the space is higher on one half compared to the other. I think Grinding large area will be difficult, so do I need to bring lower half to higher?

Thank you for your suggestions and appreciate your time and help

 

[highup]

Depends on if the high area is just a hump. If it's just a spot or a hump, it would be best to grind it down.
If it's a crack across the room and one entire side of the slab was lower, you'd want to raise the lower side or feather it out far enough to meet the correct tolerance.

 

[satishtiru]

Depends on if the high area is just a hump. If it's just a spot or a hump, it would be best to grind it down.
If it's a crack across the room and one entire side of the slab was lower, you'd want to raise the lower side or feather it out far enough to meet the correct tolerance.

Sorry, my picture has a line and do not have any cracks in the concrete at this time. From that line, one side is lower. High spot is around 4x4 foot. Will this be considered as hump and should I grind that area?
Thank you.

 

[highup]

Hard to tell without seeing and feeling it in person. Do you think feathering out all directions would bring it close to tolerance?

 

[C.J.]

If you put a straight edge on the imaginary line between the high side and low side but resting on the high side, how much does the floor drop off at the low side?

Do you have access to grinding equipment WITH DUST CONTAINMENT. If you don’t have dust containment I wouldn’t even consider recommending that you grind the floor cus you’ll just end up dusting out your whole house as well as breathing in a bunch of silica dust.

Self leveling is an option to fill in the low side to bring it up to meet the high side

 

[satishtiru]

If you put a straight edge on the imaginary line between the high side and low side but resting on the high side, how much does the floor drop off at the low side?

Do you have access to grinding equipment WITH DUST CONTAINMENT. If you don’t have dust containment I wouldn’t even consider recommending that you grind the floor cus you’ll just end up dusting out your whole house as well as breathing in a bunch of silica dust.

Self leveling is an option to fill in the low side to bring it up to meet the high side

It seems i have low valley on one side (left) of around 1.5 foot high hump area and then bigger valley towards low side (right side). So, when I put 6 foot straight edge, I have to press on one side towards high end (left) then I get 1/4 inch gap towards low end (right side). If I did not press on one side, level wobbles. This is Scenario 1 in my pictures

If i Put the level's left most end on that 1.5 foot high hump, it flattens out to right side. In this case, I have negligible dip (<1/16 inch). This puzzles me to see if I should even fix any part of it. This will be Scenario 2.

I have attached both pictures. I have circled part of high hump area.

I just bought 5 AMP 4.5 inch angle grinder just in case but I do not have the dust containment yet.

Thank you for your help.

 

[satishtiru]

Hard to tell without seeing and feeling it in person. Do you think feathering out all directions would bring it close to tolerance?

Thank you for your suggestion. I can try this with self levelling compound and have to slope in such a way it will not cause more problems.

 

[C.J.]

Lowes usually has these in stock or Amazon is your friend. Hook it up to a shop vac with a vacuum bag in it and you’re doin alright. Ideally you would hook it up to a HEPA vac but sometimes you just gotta roll with what you got. I believe you can fit a 5” grinding cup in that shroud.

https://www.amazon.com/DEWALT-DWE46...hvlocphy=&hvtargid=pla-4584482468345098&psc=1

 

[satishtiru]

Lowes usually has these in stock or Amazon is your friend. Hook it up to a shop vac with a vacuum bag in it and you’re doin alright. Ideally you would hook it up to a HEPA vac but sometimes you just gotta roll with what you got. I believe you can fit a 5” grinding cup in that shroud.

https://www.amazon.com/DEWALT-DWE46...hvlocphy=&hvtargid=pla-4584482468345098&psc=1

Thank you.
Do you recommend grinding that area? If there are any other options, please let me know.
Also which way is correct to check flatness (scenario1 vs Scenario2 in my picture for previous message)?

 

[highup]

There's a difference between floor patch and self leveler.
With patch you put the patch where you want it to be.
With self leveler, it not only goes flat it goes level..... Imagine feeling that area with water. Self leveler is somewhere between the consistency of chocolate milk and a warm milkshake.