OSB subfloor with 1/4" dips

[Pepper.Rivenbark]

Here's what I'm working with: I'm going to install Lifeproof 8mm with 12 mil wear layer. After I handle my dips in the OSB, I plan to top with 1/5" lauan then the Lifeproof Universal Underlayment. Maybe I'm overkilling but I want this floor to be solid! The install/warranty states for subfloor flatness tolerance '¼" in 10ft.' = I don't understand what that means?
Here's my problem:
Soooooo...I've three 1/4" dips in my OSB subfloor. The room is a rectangle, 22' x 11' and three places dip down to 1/4" over an area of about 3-4'. I've applied Henry 354 Premix Patch and Level but I'm thinking there's a better way to handle the dips. I've looked into self-leveling products but I've been baffled by the types/primers/materials to use them on. Any advice about tackling this dips would be greatly appreciated!

 

[C.J.]

Build up the low areas with layers of roofing felt. Layer them so they look like a topographical map. You can go up to 6 layers thick. If you use 30# felt, 6 layers adds up to 3/16”. That alone should bring your floor within tolerance. Best part is you can nail or staple through it and it won’t crumble like floor patch, and it is flexible so it will roll with the punches that your house throws at it during any seasonal changes.

 

[Incognito]

easy money with almost any sort of felt paper as described above

check/inspect with ANYTHING ten foot long and straight/flat

so far as the "specifications" are concerned ANYWHERE you can swing that 10' straight edge around on your substrate there should ZERO locations with more than 1/4" gap under the straight edge

 

[Pepper.Rivenbark]

Build up the low areas with layers of roofing felt. Layer them so they look like a topographical map. You can go up to 6 layers thick. If you use 30# felt, 6 layers adds up to 3/16”. That alone should bring your floor within tolerance. Best part is you can nail or staple through it and it won’t crumble like floor patch, and it is flexible so it will roll with the punches that your house throws at it during any seasonal changes.

Sweet! Thanks for that. Do you think I'm going overboard with the 1/5" lauan AND the underlayment then the LVP that has underlayment?

 

[Pepper.Rivenbark]

easy money with almost any sort of felt paper as described above

check/inspect with ANYTHING ten foot long and straight/flat

so far as the "specifications" are concerned ANYWHERE you can swing that 10' straight edge around on your substrate there should ZERO locations with more than 1/4" gap under the straight edge

Thank you!!!!!!!!!!! for explaining that

 

[C.J.]

Sweet! Thanks for that. Do you think I'm going overboard with the 1/5" lauan AND the underlayment then the LVP that has underlayment?

Underlayment (wood) and underlayment (foam) may or may not be worth it depending on what it is you are trying to achieve.

Installing 5mm? underlayment won’t give your floor any additional structural integrity like a layer of 1/2” or 3/4” will so if that’s your reasoning, save your money; or spend more and get 1/2” or 3/4”. Installing a layer of 5 MM underlayment will give you a nice clean and smooth substrate when installed over a properly prepped subfloor. If you were doing a glue down installation this would be a necessity but for a floating floor it is a luxury.

In general I don’t recommend using an additional layer of underlayment (foam) if your LVP already has an attached pad. There may be some thermal or sound transmission benefits that you will get from using an additional layer of underlayment (foam) but, at 1.5 MM thick, how much of a benefit are you actually getting.

 

[Pepper.Rivenbark]

Underlayment (wood) and underlayment (foam) may or may not be worth it depending on what it is you are trying to achieve.

Installing 5mm? underlayment won’t give your floor any additional structural integrity like a layer of 1/2” or 3/4” will so if that’s your reasoning, save your money; or spend more and get 1/2” or 3/4”. Installing a layer of 5 MM underlayment will give you a nice clean and smooth substrate when installed over a properly prepped subfloor. If you were doing a glue down installation this would be a necessity but for a floating floor it is a luxury.

In general I don’t recommend using an additional layer of underlayment (foam) if your LVP already has an attached pad. There may be some thermal or sound transmission benefits that you will get from using an additional layer of underlayment (foam) but, at 1.5 MM thick, how much of a benefit are you actually getting.

Thank you sooooooooooooo much for taking the time to help me out!

I'm trying to achieve the most luxurious flooring possible. I've been working on this room for years and it's finally time for the floor!!!! I don't want to cut any corners or pinch pennies. I'm not loaded at all but I've taken my time, done all the work myself, waited for sales and here's where I spend money to make this room perfect! I never realized how important a good solid floor was until I lost mine due to an unsealed sill on an exterior wall that was below grade at the bottom of a hill. So. Much. Water flooded in. 7 weeks after closing on my first house. Hence the new wall, the waterproofing, the excavating and the grading. Now I get my floor back and I want that baby to be plush!

The OSB that's down is brand new and has never had any flooring installed before. Wall and joists all new wood as well. We've been walking on the subfloor for about 4 years (yes, it's taken me that long). See below. I've secured, worked out any creaks and shimmed and filled voids and it's solid. With that info, would you say using the 5 mm underlayment (see below) would go toward that luxury that I'm going for? (installed once the dips are filled, of course

The thermal benefit of the 1.5 mm underlayment would be nice considering the room's location BUT I don't want to a. waste money if the benefit is negligible and b. go overboard [I read another thread where a guy spoke about the possibility of laying too much under the click lock planks and that compromises the click locky-ness (eloquently said, I know] ~thoughts on that?

And so you see my dips (hahahahahhaha) I attached some pics as well. The putty knife black line is a 1/4" mark. The 1st photo is at the low point and the other two are moved to the right a bit.