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-   -   Bouncy mortar bed (http://www.diychatroom.com/f5/bouncy-mortar-bed-24839/)

padola07 08-06-2008 07:34 PM

Bouncy mortar bed
 
I am currently remodelling my bathroom floor and so far my unlevel floor has eaten me alive. The floor evenly slopes about an inch from the back wall up to about 4 feet into the room and then slowly but surely levels off as you move away from the back wall.

Now my neighbor, an (old school) mason by trade, suggested we pour a mortar bed. We did, about an inch plus thick. Now there is a big crack in the bed (about 2ft long) that appeared right after it was poured. That I am not as worried about as I am about the fact that around the edges of the room when you step on the mortar bed you can feel it move. In the bad spots you can actually hear it clang against the sub floor.

Basically we put down a vapor barrier and then poured the mortar no wire mesh or felt. I thought that was a mistake but the "expert" said that was fine.

Has anyone ever seen a bouncy mortar bed? Is the lack of wire mesh the problem? If so you do i have to dig up and start over. I paid $300 for the labor but my neighbor is not being helpful at all.

Appreciate any thoughts.

Thanks

Big Bob 08-07-2008 06:39 AM

Mortar beds are very old school...so I'M I...but never ever only 1" thick... more like 5" to 6" or better. stop right now before you waste even more money.

Get a pro to look at this....hire them for a consultation.

Lots of factors to get right before you tile...

Bud Cline 08-07-2008 07:06 AM

Mortar beds for tile (by the book) generally have a minimum thickness of 1-1/4". In some cases 3/4" is acceptable. In this case you don't "pour" them, you place and pack them, then screed them off smooth. You use a very dry mixture of sand and Portland cement. The mix is a ratio of 4:1 or 5:1 sharp sand to Portland.

Wire is a requirement along with a device to seperate the subfloor from the cast, something such as roofing felt. A suitable substrate (structurally) is still required. When placed on a wood frame structure you stay away for a couple of days to allow the mix to do its thing. Walking on the floor too soon with a flexing structure will only cause a flexing new floor.

Have no guess as to what went wrong except that if too much water was used to make the mix "pourable" to the point of being self levelling then there's the problem right there maybe.:)

padola07 08-07-2008 07:08 AM

Really? A 6 inch floor? That would require a step from the hallway into the bathroom.

I have thought about consulting another pro. My neighbor is actually a pro. he owns a stone and masonary company and he's been doing this since before I was born. That makes him a little stubborn when it comes to looking at other ideas.


One solution that a novice has floated to me was to get masonary screws and screw the mortar bed into the floor joists below to keep it stable. I'm not in love with that idea. I'm thinking rip out everything eat, the expense and level the floor by sistering all the floor joists.

Really desperate right now and would appreciate any guidance.

Thanks

padola07 08-07-2008 07:20 AM

Bud,
Here's exactly what we mixed

1 bag of mortar mix
1/2 bag of a sand mix
2 shovel fulls of portland.

The mix was pretty watery... wouldn't exactly flow or pour but I far from a "dry mix". I thought it was too watery at the time but I deferred to the pro with decades of experience.

We put down a vapor barrier to seperate the mortar bed from the sub floor. What does roofing felt do?

Now given the situation I am in and yes all you guys have to go by are my weak descriptions of the situation, how can I move forward? I am not averse to starting over if there's any significant risk that the lack of wire mesh and felt, the bouncyness of the floor and the large crack that appeared immediately after pouring can cause problems with my tiles in the future. However if there's any ideas on a fix I would be interested too.

Thanks so much for the replies! I really appreciate it

Bud Cline 08-07-2008 08:17 AM

Quote:

Really? A 6 inch floor? That would require a step from the hallway into the bathroom.
Where's that coming from? Am I missing or overlooking something here?:)

padola07 08-07-2008 08:25 AM

Quote:

Originally Posted by Big Bob (Post 146644)
Mortar beds are very old school...so I'M I...but never ever only 1" thick... more like 5" to 6" or better. stop right now before you waste even more money.

Get a pro to look at this....hire them for a consultation.

Lots of factors to get right before you tile...


Thats where I got that from. My floor is an inch and change

zircon 08-07-2008 08:37 AM

A bouncy mortar bed is doomed
 
You have to start over and make sure the subfloor is not bouncy. Suggest you also check out the John Bridge Forum which is a tile only site and there are people who are experts who will help you.

padola07 08-07-2008 08:47 AM

The subfloor (3/4 plywood) is definitely not bouncy. I have screws everywhere because at first i used drywall screws then I decided to back it up with deck screws. The bounce is the mortar bed

Thanks I will check out John Bridge

Bud Cline 08-07-2008 12:16 PM

Screws won't take the bounce out of a floor. The "bounce" is usually do to structural ammenities or the lack thereof. Either the joist members are too light or the joist span is too great for the applied load.

A mud bed properly prepared will stiffen a floor tremendously and carry its own tensile load, within reason.

Something else is happening here that hasn't yet met the eye.

What size are the floor joists?
What is their spacing?
What is their freespan distance?
What is their species?
What material is the subfloor comprised of?
How thick is that subfloor material?

Something (negative) is being overlooked or not reported here!

padola07 08-07-2008 02:16 PM

Let me see if this helps.

The entire floor does not bounce just the mortar bed on top. The subfloor is 3/4 ply secured with numerous deck screws. I have had the subfloor down for months trying decide how level the floor so i know it doesn't move. The joists are very solid, don't remember the exact the dimensions.

The variable is the mortar bed. You can literally hear it clanging against the subfloor which tells me the subfloor isn't moving. This movement only occurs on the corners and is severe at the highest point in the unlevel floor which consequenlty is where the bed is thinnest

I posted on John Bridge like someone advised and they said that the lack of wire mesh and felt on a 1 inch floor was the culprit. That sort of makes sense.

Either way, it looking like the mortar bed must be removed.

Thanks

padola07 08-07-2008 02:21 PM

My plan of action now is to lose the entire floor and level the floor by sistering the joist so thats level. Might cost me a pretty penny but I'm done with messing with mortar. That way I have a lower floor, thats level all the way to the joist and I can follow best practises for installing tile without worrying about an unlevel floor

javan 08-07-2008 02:41 PM

I remodeled my bathroom last year and had a similar problem where the floor was not level in two places. My solution was to take the entire floor, down to the floor joists, then I sistered the existing joists with taller joists, but ripped to make the floor level, then put cross bracing between the joists, and shortened the unsupported lenght with a new post in the basement. This was all done for a tile floor to go over top. I had thought of a mud bed for the tile to "level" everything out, but the thickness would be too great and the strength of the subfloor/framing was questionable. It was a hard pill to swallow to rip out the floor, but everytime I walk on it, it is solid and I know why!

Do this floor right! 1st attempt is not working, so start over! But I would not try and rely on mud/mortor or any other mix to "level" it out. I would start with the framing, and work your way up. It will take long and cost more $$, but you will happier in the long run.

Or, you can lay carpet down.

Oh, Two thumbs up for the John Bridge forum. THey helped me out immensley with floor!

Bud Cline 08-07-2008 02:54 PM

My guess is that you didn't allow for any expansion on the perimeter walls of the room. You just poured the floor tight to the walls. Once the cement cured it expanded a little and you now have a condition known as "tenting" because there is no place for the expansion to go but up. It is raising this cement in the middle of the room causing it to "crown".

That's the only thing I can think of that would account for that floor moving like you say it does. You now have me convinced it is the cement.

I had my doubts earlier but you win.:):):)

The only fix is removal.:)

Yoyizit 08-07-2008 03:30 PM

cut and pasting the OP's posts only. . .
 
The floor evenly slopes about an inch from the back wall up to about 4 feet into the room and then slowly but surely levels off as you move away from the back wall.

about an inch plus thick.

Mortar has a minimum thickness requirement.

when you step on the mortar bed you can feel it move.

So you have an air space between the mortar and the floor.

Has anyone ever seen a bouncy mortar bed? Is the lack of wire mesh the problem?

Mortar is very weak when bending forces are applied (weak in bending.")

there is a big crack in the bed (about 2ft long)

how can I move forward?

Will a crack that opens and closes depending on the load be a problem for whatever is to cover this mortar bed?

get masonary screws and screw the mortar bed into the floor joists below to keep it stable.

Masonry will crush with the concentrated force of screw heads unless you use fender washers on top of rubber washers, and maybe even then.

The subfloor (3/4 plywood) is definitely not bouncy.

Then the air gap and mortar being weak in bending gives the bounce.

This movement only occurs on the corners and is severe at the highest point in the unlevel floor which consequenlty is where the bed is thinnest

So the mortar bed is moving as two single rigid bodies [if no crack, then as one single rigid body].

It can stand the bending force you have put on it so far, so wire mesh is not needed.
The mesh keeps broken pieces together but it does not add strength [unless you get prestressed concrete, in which case the reinforcing metal is first stretched, so the concrete is always in compression, where it is the strongest].

The argument that someone was "doing this before you were in diapers" doesn't hold much water with me.

Maybe you can fill the air gap, from below, with caulk or elastic material or a material that becomes rigid when it cures.
You only need support in a few places to make the whole bed stop bouncing.


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