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Old 09-12-2019, 06:48 PM
 
154 posts, read 52,289 times
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I am taking up tongue and groove wood flooring in my home preparing to have porcelain tile installed. When I pulled up the pad beneath the tongue and groove flooring I noticed that the floor had about a 7/16" wide groove in it that ran the length of the floor. It extended under that walls too so it appears to have been put there before the walls went up. This house is 20 years old so it baffles me as to what the purpose of this groove was. It doesn't look any typical cement saw cut. The floor has no cracks in it whatsoever. My tile installer won't be looking at the floor for another week so I'm sort of curious as to what this big groove is for. I've not seen anything like this before.

I tried to post a photo but this website is not cooperating. Has anyone encountered anything like this before? Not sure why I can't post a picture of this.
Attached Thumbnails
Large groove in concrete floor in bedroom-20190912_102524.jpg  

Last edited by Veniceman; 09-12-2019 at 06:52 PM.. Reason: Trying to post a photo
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Old 09-12-2019, 07:22 PM
 
Location: Rochester, WA
6,234 posts, read 3,478,575 times
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It does look like a concrete saw mark, it tends to chip the edges like that as it cuts. Question is why.... Can only assume some kind of plumbing had to go in or be changed after the slab was in. Does it line up with plumbing in the house? Like it's headed someplace that makes sense?
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Old 09-12-2019, 08:02 PM
 
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Definitely to wide and has a smooth top edge so I would venture to say it’s a pour stop that also acts as a control joint. They just have formed and poured half of the slab, stripped the form send then poured the remaining half the next day or so but not sure why it’s that open? They could have had a fibrous expansion material in there but not sure why it’s not visible.
Whatever they did, I’m assuming they did some good concrete work since you mentioned the absence of any cracking.

Now that will act as an expansion point in the slab and your tile contractor should fill the joint and cover it with an uncoupling membrane (crack isolation membrane ) which will allow for expansion of the tile on one side of the “ control joint “ that’s in the concrete slab. That will prevent the tile over the joint from cracking due to the expansion and contraction of the slab. ( effectively two slabs butted at that joint ) The installer should be familiar with all of the different manufactures that offer this product, there are many.

Last edited by Rickcin; 09-12-2019 at 08:16 PM..
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Old 09-13-2019, 03:47 AM
 
154 posts, read 52,289 times
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Quote:
Originally Posted by Diana Holbrook View Post
It does look like a concrete saw mark, it tends to chip the edges like that as it cuts. Question is why.... Can only assume some kind of plumbing had to go in or be changed after the slab was in. Does it line up with plumbing in the house? Like it's headed someplace that makes sense?
It doesn't appear to be plumbing related. There is an ensuite bathroom but this groove isn't close to it nor does the groove appear to be running in a direction where it could be leading to it. I'll see if I can edit this and post a close up picture of that groove.
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Old 09-13-2019, 03:56 AM
 
154 posts, read 52,289 times
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Quote:
Originally Posted by Rickcin View Post
Definitely to wide and has a smooth top edge so I would venture to say itís a pour stop that also acts as a control joint. They just have formed and poured half of the slab, stripped the form send then poured the remaining half the next day or so but not sure why itís that open? They could have had a fibrous expansion material in there but not sure why itís not visible.
Whatever they did, Iím assuming they did some good concrete work since you mentioned the absence of any cracking.

Now that will act as an expansion point in the slab and your tile contractor should fill the joint and cover it with an uncoupling membrane (crack isolation membrane ) which will allow for expansion of the tile on one side of the ď control joint ď thatís in the concrete slab. That will prevent the tile over the joint from cracking due to the expansion and contraction of the slab. ( effectively two slabs butted at that joint ) The installer should be familiar with all of the different manufactures that offer this product, there are many.

The width of this control joint puzzles me. For awhile I thought perhaps they added this bedroom on after the house was built but that makes no sense at all. It's a 2 bedroom home and this is the master suite. That groove heads toward the adjoining living room so I'll know more when I get that flooring up today. I'm curious of that groove runs clear across the house into that living room. It doesn't run into the dining nook because I took that floor our yesterday and it is not cut or cracked at all.

My tile guy had a death in family and wont be back in Florida for a week. I'm hoping he can explain it to me. I agree with your assessment about the membrane though. This is a good tile installer so I'm sure they will do it correctly.
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Old 09-13-2019, 04:09 AM
 
154 posts, read 52,289 times
Reputation: 181
Quote:
Originally Posted by Rickcin View Post
Definitely to wide and has a smooth top edge so I would venture to say itís a pour stop that also acts as a control joint. They just have formed and poured half of the slab, stripped the form send then poured the remaining half the next day or so but not sure why itís that open? They could have had a fibrous expansion material in there but not sure why itís not visible.
Whatever they did, Iím assuming they did some good concrete work since you mentioned the absence of any cracking.

Now that will act as an expansion point in the slab and your tile contractor should fill the joint and cover it with an uncoupling membrane (crack isolation membrane ) which will allow for expansion of the tile on one side of the ď control joint ď thatís in the concrete slab. That will prevent the tile over the joint from cracking due to the expansion and contraction of the slab. ( effectively two slabs butted at that joint ) The installer should be familiar with all of the different manufactures that offer this product, there are many.

I'm trying to attach a close up photo but this website isn't cooperating with me. I'll try to shrink the photo a bit and try to attach it.
Attached Thumbnails
Large groove in concrete floor in bedroom-20190913_060439.jpg  
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Old 09-13-2019, 06:54 AM
 
1,947 posts, read 669,524 times
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I saved the photo and then enlarged it to get a better look and still believe it’s a pour stop however I cannot explain why!

Does the shape of the slab change beyond this joint? The explanation could be as simple as one side of that joint was ready for concrete so they decided to pour the slab at two different times? I don’t think we’ll ever be able to explain it as well as why the joint is so wide.

Regardless, as long as your contractor deals with it properly, your flooring should be fine.
I’ve come across a similar situation but a piece of one by lumber was left in the slab and the ceramic tile reflected the joint and cracked. After the flooring was removed, I had the wood from the joint removed, filled the gap and recovered with a membrane & porcelain tile and never again had an issue!
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Old 09-13-2019, 12:05 PM
 
Location: Rochester, WA
6,234 posts, read 3,478,575 times
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We may never know... and you're right it may not really matter.

But... I still think it looks like a cut because of the chipping at the edge and the fact that it's not perfectly straight like it's following a form, but both sides match.
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Old 09-13-2019, 02:17 PM
 
1,947 posts, read 669,524 times
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Quote:
Originally Posted by Diana Holbrook View Post
We may never know... and you're right it may not really matter.

But... I still think it looks like a cut because of the chipping at the edge and the fact that it's not perfectly straight like it's following a form, but both sides match.
It did follow a form, they formed with wood poured the concrete, then stripped the forms and poured the the opposite side against the recently placed concrete. I know it was saw cut due to the slightly rounded top edge, width of the joint and primarily because there’s a slight curve in joint. A concrete saw would not be able to cut to a slight radius.
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Old 09-13-2019, 04:21 PM
 
154 posts, read 52,289 times
Reputation: 181
Quote:
Originally Posted by Rickcin View Post
I saved the photo and then enlarged it to get a better look and still believe itís a pour stop however I cannot explain why!

Does the shape of the slab change beyond this joint? The explanation could be as simple as one side of that joint was ready for concrete so they decided to pour the slab at two different times? I donít think weíll ever be able to explain it as well as why the joint is so wide.

Regardless, as long as your contractor deals with it properly, your flooring should be fine.
Iíve come across a similar situation but a piece of one by lumber was left in the slab and the ceramic tile reflected the joint and cracked. After the flooring was removed, I had the wood from the joint removed, filled the gap and recovered with a membrane & porcelain tile and never again had an issue!

I sent my tile guy a picture of it. He said it was a control joint but couldn't explain why its 7/16" wide. He said it wont be a problem though. As I was tearing out the adjacent living room flooring I saw that a similar groove had been cut. This groove connect to the bedroom groove and took a 90 degree turn and followed along the living room wall.

I've torn out carpet and tile before on a slab home but didn't see anything like this. It's really pretty wide.ooka like they did it with a hoe!

The concrete doesn't change shape.
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