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Old 10-01-2012, 01:16 AM   #1
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Leveling subfloor for hardwood over asbestos tiles


Greetings DIY Chatroom folk,

I've been reading posts for years on this chatroom, and given the reliability of threads, I've never needed to sign up and create a thread until now.

Trying to keep it brief-

1953 home with asbestos composite tiles laid on top of 2 separate layers of subflooring that total 1.5" over the joists; from the looks of it when pulling out the HVAC vent, its 2 separate layers of wood subfloor. Most of the house has real nice wood floor under the carpet, except the den with asbestos tile. The room in question has a crawl space below it.

Although generally pretty level, there are some spots that sag enough that I believe it would be wise to level out before installing either cabin grade unfinished hardwood (to be sanded and stained along with the rest of the house) or parquet wood tiles- whichever I can find on the cheap.

Between this chatroom and reliable internet sources at large, I can't seem to find a consistent answer- should I level using thin set style leveling before I install the 1/4" plywood, after I install the 1/4" plywood, or does it not matter? I'm thinking I would not have to sand the leveler if I put the plywood on afterwards...

If indeed its better to lay the plywood after the leveler, is it OK to use a thinset mortar typically used for ceramic tile? Its about half the cost of the standard subfloor leveler...

Any input on anything else I might want to add into the equation to seal the asbestos tiles would be appreciated as well.

Thanks much!

JKB

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Old 10-01-2012, 08:17 AM   #2
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Leveling subfloor for hardwood over asbestos tiles


I'd be working under the house to figure out why there's a sag and fix that instead of trying to fix it from above.

There is no need to Seal the floor since your just going over it with a soild surface. Only time there's a remote danger is if you start cutting out the flooring.
There's also no need to add a layer of 1/4 plywood, you would only use that if you were going to be laying something like linolium or glued down tiles.

Take a look around before doing anything to see how rasing the floor even more then it is now is going to effect the baseboards, door openings, transitions to other floors. That floor is already really high.

Consider a prefinished hardwood or even engineered flooring instead of having to go rent all the equipment, buy the sand paper, cleaners, stain, and sealer.
Your not going to be saving any money by finishing on sight and will have no where near the layers of finish as a prefinished floor will have.
Plus no smell and can be walked on the same day it's installed.


Last edited by joecaption; 10-01-2012 at 08:20 AM.
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Old 10-01-2012, 08:55 AM   #3
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Leveling subfloor for hardwood over asbestos tiles


More information is needed----you may have a subfloor nailed to the joists--then a 1x2 sleeper (furring strip) then a layer of plywood.

This was done to allow electrical conduit to be placed along side of the sleepers and sandwiched between the subfloor and the top flooring.

Driving hundreds of nails through that to hold the hardwood is like playing Russian Roulette---

Let us know exactly what you have---the top layer may need to be removed--additional furring strips added--and the hardwood nailed to them.
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Old 10-01-2012, 12:24 PM   #4
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Leveling subfloor for hardwood over asbestos tiles


Thanks for the input fellas.

O.M.-

I'm going to do some crawling around right now to investigate, I should be able to figure out if there is a furring strip or not. Everything is quite accessible, plus there is 2 vents cut. I'll take a photo or two and post in a little while.

J.C.-

As 80% or so of the house has wood floors already laid (of which I've pulled the carpet already), but in need of refinishing, I figured I would install wood in the den too and then sand/stain along with the rest of the house in one big go. Have you installed wood floors directly over composite type tiles before? Seems like most folks swear by plywood, then underlayment, then hardwoods... I'm definitely all ears if I could bypass a step or two...

Lastly, to clarify-

Sag might not be the best word for the state of the floor; there is a couple spots that have are ever so slightly lower than the center of the room. I'm nearly certain any flooring could be installed over this with no problem, but as this is my first home I'm being particularly OCD about it...

Thanks for the input!
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Old 10-01-2012, 07:50 PM   #5
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Leveling subfloor for hardwood over asbestos tiles


When nailing down 3/4" hardwood---shims can be used to offer a solid nailing area in a low spot---If the plank is bridging a hollow ---tuck in a wood shim---

It's high spots that are a bigger concern---hollows can be shimmed---
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Old 10-02-2012, 07:02 PM   #6
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Leveling subfloor for hardwood over asbestos tiles


Thanks O.M.!

To my surprise when picking up the luan boards, a big box store worker got to picking my brain about the project and suggested the same thing. You guys are the first I'd come across this method to go about it.

Let me ask you a handful of questions on this if you don't mind-

Do you think that it would be better to lay the luan first, and then shim the 3/4 hardwood as I go? The flooring guy seemed to suggest that I level the luan with the shims that way the flooring boards will go down that much quicker.

As far as the two rooms, they are both a very gradual low spots, so I think the shim method will work great. The subflooring is not furring strips to create a space for running electric; there is indeed 6 or 8 inch diagonal wood boards, with another layer of 3/4 plywood on top of the diagonals. Asbestos tile is on top of this (In surprisingly good shape- I thought about epoxying them in for a while...)

Just to confirm/double check- both rooms will get a layer of vapor barrier prior to the flooring, right? For the room with asbestos that is getting a layer of 1/4"luan, the wood grain needs to go perpendicular to the joists, with the smooth side up? Probably an obvious one, but thought I'd run it by you- the shims will go perpendicular to the flooring boards as well, correct?

Thanks so much for your input!

I'll post some pics in case this might help someone else down the line.
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Old 10-02-2012, 09:56 PM   #7
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Leveling subfloor for hardwood over asbestos tiles


Quote:
Originally Posted by J. K. Brennan View Post
Thanks O.M.!

To my surprise when picking up the luan boards, a big box store worker got to picking my brain about the project and suggested the same thing. You guys are the first I'd come across this method to go about it.

Let me ask you a handful of questions on this if you don't mind-



Do you think that it would be better to lay the luan first, and then shim the 3/4 hardwood as I go? The flooring guy seemed to suggest that I level the luan with the shims that way the flooring boards will go down that much quicker.

Yikes!! Why put down Luan? That stuff is soft and doesn't hold nails or staples well----



As far as the two rooms, they are both a very gradual low spots, so I think the shim method will work great. The subflooring is not furring strips to create a space for running electric; there is indeed 6 or 8 inch diagonal wood boards, with another layer of 3/4 plywood on top of the diagonals. Asbestos tile is on top of this (In surprisingly good shape- I thought about epoxying them in for a while...)

Fine surface for 3/4" oak---do a test--if the cleats or staples are not penetrating the VA tile--it will need to be removed---

Just to confirm/double check- both rooms will get a layer of vapor barrier prior to the flooring, right? For the room with asbestos that is getting a layer of 1/4"luan, the wood grain needs to go perpendicular to the joists, with the smooth side up? Probably an obvious one, but thought I'd run it by you- the shims will go perpendicular to the flooring boards as well, correct?



You have a very stuff subfloor---you could run your planks with or across the joists without issue----

I use felt paper under all floors---however it is not really needed on a second floor install--only over a basement or crawl space.




Thanks so much for your input!

I'll post some pics in case this might help someone else down the line.

I hope you can find my answers inside the 'quote'
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Old 10-03-2012, 09:23 AM   #8
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Leveling subfloor for hardwood over asbestos tiles


Another thank you!

Not exactly what I wanted to hear, but good food for thought...

My original decision for the 1/4" underlayment (decided on from various research/discussions) was to help "seal" in the asbestos... As this room is above a crawl space, perhaps a thicker felt paper instead of luan could accomplish the same thing? Apologies for asking you so many questions, this is my first go at T&G hardwoods and I prefer doing things right the first time if possible- what are your thoughts on using shingles to help level things out a bit? Some folks swear by this, and for my application it seems like it could help reduce the amount of time working with shims...

As I'm reluctant to do abatement myself on the tiles, should staples not fasten satisfactorily- would a thicker plywood be kosher to create a stout staple/nail mating surface?

And lastly, as I've heard about a 50/50 mixed review as far as do/dont: the smaller room in the addition has 3/4" particle board. What are your thoughts on stapling/nailing 3/4" hardwood into this subfloor material?

If you are ever in Nashville, I owe you a beer/coffee!

JB
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Old 10-04-2012, 07:13 PM   #9
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Leveling subfloor for hardwood over asbestos tiles


Sorry for the lag in responding---I have been leaving for work at 4:30 AM and not getting home till 6:30 or so---


Your floor---1/4" Luan is out---you would be better off with nothing than that stuff---see if the gun will shoot through the old vinyl without bending the nails or staples --if it works---nail right through the old tiles---(after you roll out some felt paper)

If you wish to ass a layer of ply on top--use 1/2" bc---stapled with 1/4" small crown staples every 8" or so---

As to removing the old VA tiles---the hazard is not that bad---your state has instructions for removal by the home owner---Only the air borne dust is a problem---wear a mash---cover surfaces with plastic---tape off the room---dampen the area as you work---use fans in the window---
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Old 10-07-2012, 03:28 AM   #10
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Leveling subfloor for hardwood over asbestos tiles


No worries on the response time! Your sound input is very appreciated. Particularly- the caution on using Luan, which I'll be able to return as I did not put any holes in it...

For reference, for anyone else who might come across this thread, I've taken some of my approach from this article: http://www.oneprojectcloser.com/how-...truction-felt/

I believe this will work well for my application, given the circumference and casual (but apparent) gradient of the sag. My first line of attack in the den with the asbestos tiles is to use 3" decking screws. I discovered that the first joist laid was 15 3/4" distance from the next joist, and then consistently 16" thereafter. There is 1.5" of wood subflooring (2 separate 3/4" layers), and I noticed when in the crawlspace that nails had often missed the joists. In some cases they probably just caught an edge; in other cases it looks like the joist was missed entirely. Several properly measured chalk lines I laid over the joists reveal that the hairline fractures in the tile consistently run about 1/4" away from the chalklines. I'm going to see how much sinking some coarse thread screws into the joists might correct the un-flat areas, or at least prevent future problems with the hardwoods. Fortunately, this scenario/problem does not plague the entire house!

I'm going to let some time pass on this bigger room to see how much the subfloor adjusts after screwing, and then use shingles where need be. I'm definitely heeding your advice on how the flooring fasteners work with tile and/or shingle & tile. Removal of asbestos tile per local code if need be.

I'll be first turning my attention to the smaller room- its a room with OSB subflooring (11' x 13', a 1970's addition), and there is some slight gradient issues. Although there is mixed reviews of hardwood fastened to OSB, I'm going to exercise caution and go with 3/8 or 1/2 plywood fastened to this OSB. While 3/8 is somewhat cheaper and lighter, using the shorter staples into 1/2" plywood makes a lot of sense to me given that effort/$ is going to be put into an underlayment.

As for the ply over OSB, any advice on laying this? Should the boards have an 1/8" gap where they meet? I've come across this idea occasionally. I'll definitely follow common wisdom as far as expansion room at the wall edges for underlayment & hardwood, but space or no space at the seams of the underlayment has me scratching my head a little bit...

I'll follow up with pics demonstrating success/frustration encountered in a few weeks when I'm done.

Thanks!

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Old 10-07-2012, 04:32 AM   #11
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Leveling subfloor for hardwood over asbestos tiles


That debate over gap or no gap has been going on forever----with exterior sheeting I leave a gap--with flooring I do not--

Hardwood will span just about any gap---so you choose---It's just not a big deal----

Keep us posted on the shimming---I've never used shingles to fill in low spots---I believe it will work---but cant say that I've ever tried it---
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Old 10-07-2012, 09:51 PM   #12
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Leveling subfloor for hardwood over asbestos tiles


A quick follow up to my last post-

The addition room with OSB as the upper subfloor surface turns out to be sitting on 1/2" or 5/8" plywood that is sitting on the joists. I'm thinking this might save me some time and $...

So long as I inspect the plywood from below for rot and there is none, I'm thinking I might be able to get some longer cleats, 1 1/2" or 2" so they will sink into the wood. From what I've read, OSB's problem as a mating surface is its inability to hold fasteners that result in squeaks. OM or anyone else out there- is there any conventional wisdom that would recommend against this (amateur) speculation?

Its too bad that the plywood is not 3/4", I'd just tear out the OSB... I'm pretty sure 1/2" over 16" joists would not be the best idea...

A possibly pleasant surprise, and the last question out of me before I get to work!
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Old 10-08-2012, 05:25 AM   #13
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Leveling subfloor for hardwood over asbestos tiles


In my experience--and my two hardwood floor guys---staples hold better than cleats----

However the cleats may be needed to penetrate the old VA tile---
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Old 10-08-2012, 07:38 PM   #14
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Leveling subfloor for hardwood over asbestos tiles


As always, good food for thought OM!

Just to clarify- the smaller room I'm decided to do first does not have asbestos tile; the bigger room in the den that does have asbestos tile has ample plywood beneath.

Also, upon closer inspection I realized that the smaller room w/o asbestos tiles has 3/4" particle board, not OSB as the top subfloor layer. Beneath this particle board is 1/2" or 5/8" plywood. I'm thinking I'll tear out the particle board and replace with more plywood since the existing plywood is not thick enough. Any advice on thickness here? I'm wondering if I could get away with adding 3/8" plywood over the existing layer of plywood and use fasteners long enough to penetrate both layers. Does this seem like a sound idea?
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Old 10-09-2012, 03:40 AM   #15
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Leveling subfloor for hardwood over asbestos tiles


3/8" will work---I'd use whatever keeps the two floors on the same plane---

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