LVP but undulating floor

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culeboards

Member
Joined
Feb 22, 2021
Messages
5
Location
Winston-Salem
1974 undulating sub-floor. Want to install LVP but (a) there is a peak in the floor at 1/4" height; and (b) I noticed that some LVP is very rigid while others are quite flexible (cork backing).
Making structural changes would be major and undesirable.
Is 1/4" manageable? Especially with the more flexi planks?

Thank you
 

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By undulating do you just mean unflat or do you mean there is significant structural MOVEMENT underfoot?

If it's only a quarter inch out of flat fix it. I shouldn't be more than an 1/8" over 6' or 3/16" over 10'. I cant see what your substrate is so I can't specify HOW to flatten. There are cementitious patching materials and there's also underlayment grade ply. Other types of (floating) floors can be flattened with layers of felt. That gsuenerally applies to heavy gauge materials, certainly not 2-3MM gauge.

My basic recommendations is GLUE DOWN over floating
Secondly, over concrete use cement based patch (Ardex). Over wood substrates use plywood.

If the substrate is structurally unsound I recommend carpet with a heavy pad.
 
Thank you.
Unflat - a big level centered on the peak will teeter totter.
Other areas have lesser differences going the other way. Bought this 1974 house 6 months ago.
There is a crawlspace, then the 2 layers of wood sub-floor (top layer is mostly crap glue/particle board(?) - awful - especially when cats pee on it for 20 yrs!! LOL ugh
Under the peak are major support beams and brick pillars, etc...
I'm hoping it can be sanded, and levelled enough with compounds (or whatever) and then I buy cork backed flexible planks.
 
If you have a layer of particle board just stare at it really hard and it will probably sand out.....
Jokes aside, you could sand through that whole top layer where your beam runs and be laser flat and voila problem solved. However to answer your initial query, it is a huge problem... with a simple solution
 
Like incognito said. Don't skip when making the floor flat. It's one of the most important jobs of the installation. I
If you can afford to replace the floor, then it doesn't matter if the floor is flat or not, because you can afford to do it over again. 😁
There are high spots and there are low spots.
If the biggest culprit is a high spot, then sand that area down if at all possible instead of feathering out from the high spot.
 
Great, thanks.
I am now noticing that at one end of the floor (near the fireplace) the peak is near 1"(!) - still OK to sand? Or should I remove the top sheet of chip board (all of them across the peak), sand the plywood beneath as much as possible, and then replace the top sheets with a lesser thick sheet (of plywood). ??
 
So, I am just going to say it. No one here can tell you the way to fix your floor. We can offer advice based on issues IN floors, but probably not entirely specific to YOUR floor. To get an idea of how to repair any substrate to allow for floor covering installation one really needs to develop and mental topographical map of said floor..... or i suppose a hard copy of one. Problem being you say something like X is high and Y is high, and we tell you to sand those, but we are all missing that there is in fact something low and X and Y are nominal and the like. Basically it goes a little like this, examine your entire substrate, determine a nominal height it is supposed to be and then do anything in your power to correct anything that is incorrect. There really are only two options. Fill or Sand.
You can sort this out.
If anyone was in your home, no one would hesitate to tell you exactly what to do, its just very hard over the interwebs. No matter what you do/think, do not listen to anyone who says self leveller is a good idea in this situation.
 
Great, thanks.
I am now noticing that at one end of the floor (near the fireplace) the peak is near 1"(!) - still OK to sand? Or should I remove the top sheet of chip board (all of them across the peak), sand the plywood beneath as much as possible, and then replace the top sheets with a lesser thick sheet (of plywood). ??
What Mark said is true, that we can only give advice because we can't see this in person.
One time I had a floor where from a point 2 1/2 ft inside the house to the exterior wall, rose 3/4 of an inch. This kitchen was directly above a garage. I cut and removed the underlayment about a foot and a half back and replaced the old underlayment with strips of thinner underlayment.
I think it started with 3/4 in plywood or particle board. It's probably been nearly 30 years ago, so I don't recall exactly what I did, but I probably put in a 6-in strip of half inch plywood and then a 6-in strip of 3/8 plywood to create a taper towards the exterior wall, then filled it with a floor patch.
Part of what you have depends on whether your underlayment has structural properties that need to be maintained.
It's a tough call without actually seeing your home.
 
I did one about 5 years ago that was a 2 inch rise to buddy's garage footing wall. Same thing, laid so many different sheets of different sized plywood over a 4 foot section it made my head spin, essentially built a ramp out of layers of plywood and topped it all in 30# felt to "smooth" it out. Pain in the nutz but the job got saved. Thats the same house i went down into the crawl space and raised a section of floor joist with a 20 ton bottle jack then braced it with a 4x4 pressure treated post. What low spot :p For the record, it is scary as balls jacking someones house up from underneath it... especially when you don't really know what you are doing.
 
At a friend's house there were four full length foundation walls front to back. There is a hump as you entered the kitchen. I cut a 2 ft by 4 ft section of plywood out of the floor to discover that two 2x10s spanned from opposite directions directly over one of the foundation walls. Each 2x10 overlapped each other by about a foot. The home had settled a little bit and those 2x10s acted like scissors lifting the floor up to create an odd bump. I think I used a reciprocating saw and a sawzall and sander to trim the top of those 2x10s flat then I replace the plywood. every job is different and sometimes you have to get creative. I've never jacked up before. I've got to draw a line somewhere.
 
I raised the main beam on my old house about 3 inches one day with the same bottle jack... it didn't kill me and that house was 100 years old. I figured that if that did not kill me then trying to raise buddies one joist up 3/4 inches or so could not be so bad.
I have removed entire subfloors to reinstall/plane/cut joists out of peoples houses. When it comes to structural repair work, there is not a lot I have no tried and mostly succeeded at.
Suppose I could take the Craig's List approach and just Self Level everything... without primer/lath and overwater it all. That seems to work :p
 
Tom, one of our "guests" here, came here and started asking questions before installing a laminate floor. Actually I think it was cortec. He leveled up his house and watching his journey was a real treat. Maybe someone can direct you to that link if I can't find it. Watching the work that Tom did I think he'd make an excellent installer. There are a couple classes of do-it-yourselfers. The ones at the bottom of the scale should not own screwdrivers knives or measuring tapes. Have you ever end of the scale are guys like Tom. Even though some of this I think was new to him his brain thinks like a mechanical engineer.
 

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