plywood subfloor is more unlevel than I thought


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Old 12-05-05, 06:35 AM
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plywood subfloor is more unlevel than I thought

Are there any better or more effecient ways to try and flatten the subfloor?


After ripping everything up and checking the floor for flatness. It is worse than I anticipated. I bought roofing felt and shingles. I am not sure which is the real cause but is most likely both. If it was shoddy construction or settling of the place. Is actually a townhouse in a complex.


Well actually now that I think about it I have no experience with this, so no idea if my place is that bad or not. But essentially there are A LOT of ups and downs on the floor. The floor falls away slightly at all walls, this should be easy to fix with the shingles and felt. There are two highspots that run from all the way across the townhouse. I guess I will have to try to sand these down a bit.


Is the solution just a lot of hard work on my part by sanding and using the felt/shingle technique or is there another option? Does it make a difference which way I try to fix the flatness? I imagine it would be easier to raise the lower spots with felt and shingles than to sand down the highspots without getting any large power tools.


Does the floor being actually level matter?? Flatness is more important correct? Within reason of course.
 
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Old 12-05-05, 12:45 PM
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Flat subfloors are important for proper flooring installation. Sand the high spots and fill the low spots with a self-leveling compound. You can check flatness with a long straight edge like a 2x4 or by having someone help you stretch a string across the floor.
 
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Old 12-05-05, 03:27 PM
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Degree of flatness and what you do about it can depend on what your laying. What are yo laying?
 
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Old 12-06-05, 03:24 AM
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John, its best to sand the high spots first before you tackle the low areas.

Like Marco said, we would need to know what kind flooring and how you are going to fasten it down.

Never use a self leveler unless you are doing a glue down or float. Even then I would use something trowable like Mapei Planipatch. A self leveler (SLC) can get you in trouble real quick if you don't have any experience using it.

If you stapling or nailing then you should not use any sort of portland based patch underneath the flooring.
 
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Old 12-06-05, 05:47 AM
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laminate flooring

I am installing laminate flooring.

The subfloor is plywood, is a patching compound the way to go?

I thought this could be done using shingles and some roofing felt to build up the low spots.
 
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Old 12-07-05, 02:46 AM
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Under a laminate I normally will use felt, shingles or 90lb roll roofing to build up the low areas. I use the patch if the problem area is underneath a transition.
 
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Old 12-07-05, 06:51 AM
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Should I be securing the felt and shingles down in any way?

The floating floor can move slightly with the expanding and contracting, will this move the shingles or felt at all?
 
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Old 12-07-05, 01:15 PM
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Sorry to jump into this post but I am always confused about this shingles business.

If I use shingles, do you cover them with something? If I just put down shingles, would I not have ridges where the shingles overlap? Wouldn't the bumps be against specs?

If anyone has a picture of how they have used shingles or roofing felt, I would sure appreciate seeing them.

(I'm curious also about whether they get nailed down or not)

Thanks.
 
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Old 12-07-05, 01:52 PM
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From a previous post on here, I cannot find it again, always have problems finding things with the search feature on this forum.

Anyway from what I recall, it was recommended to use roofing felt, which is from what I can tell a really think strong paper. You can use that for that small dips, but the bigger ones. It was said to make a sandwich with a layer of roofing felt then a shingle then another layer of felt.

This smooths out the transistion so there is no hard edge or sudden level jump. Perfectly flat is not easy or required, the floor needs to be within a certain spec and from what I have read this fixes that.


Although I still do not know if I am supposed to affix it to the floor somehow or just let it lie there. On nail down flooring, the nails themselves hold it in place, but not sure about the laminates, which is what I am installing.
 
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Old 12-07-05, 02:15 PM
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John, I asked once before about nailing the shingles down and the reply was that the nails in the subfloor would hold them in place. However, in my scenarios I would not use a subfloor. I did put in a subfloor once but I wonder if I should have leveled under or on top of the new subfloor?

I have hacked in a few laminate floors for friends and acquaintances and in four rental places but have never levelled. I have offered to but people don't want to take the time and I always seem to be under a deadline. So far, once the furniture and applicances are in place, the floor seems fine even though there have been some hefty dips and rises. Everyone is very happy and I keep getting referals, which I try to discourage cause I'm no pro. I lose about a months sleep every time because I never levelled. Two floors are over 3 years old, no problems.

Next floor, I want to learn how to level.
Thanks for the sandwich info. That helps
 

Last edited by mjd2k; 12-07-05 at 02:25 PM.
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Old 12-08-05, 01:59 AM
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John, I rarely have to use shingles. When I do, I cut them and use them to "start" to fill in a very bad area. I also use a layer of felt between the roofing if I have to go more than I layer.

Every layer should be a different width so you would start narrow and get wider as you build up.

As I get it built up I do the final "feathering" out with 15lb or 30lb felt.

Over plywood I use a staple gun to hold it in place until its covered.
Over a slab I use tape.
 
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Old 12-08-05, 02:59 PM
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thought i'd jump in here. If you are using this method for a basement with concrete floors would you put down the poly vapor barrior first, then use the felt and shingle method for leveling or put down the shingles and felt first, then when all is level put down the poly? My hunch is to put the poly first no matter what. But if you put the poly down how do you stabalize the shingles and felt? Just liquid nails them to the plastic?

thanks, great thread here.

deacon
 
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Old 12-09-05, 04:02 AM
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I'm not sure if there is a definitive right or wrong method on this

When I have a laminate job over a slab I do all the prep work and "flattening "out first before I roll out any poly.

After that is done I roll out the poly and put together a few rows and then recheck for any low areas as I go along. I can easily fine tune over top the plastic if needed.

This is the best method for me. Every few rows you can stand back and eyeball to see if anymore felt is needed. Just slide in one or more strips until it stops, then keep repeating.

It is a little slower, but my floors are always flat this way.
 
 

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