Un-Level Subfloor

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Posted by: from Brantford
4/22/2020 at 5:34:55 PM

So as I am stuck at home I have decided to redo our floor with laminate I get to the main dining area and notice that one joist has bowed up about half inch across its span which has created a low spot on either side, I'm looking for some suggestions as to the easiest fastest and best way to correct this is, also I am laying laminate over old existing tile that is 9x9 so would prefer not to rip that up, have thought about using self leveler but would it bond to the old glue and old vinyl tile? That is what I would prefer to do rather than ripping everything apart and starting from scratch, I can also access the joist from beneath

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Date/Time4/22/2020 at 8:47:02 PM

I advice you the do a self livening and make sure the tile not a bumpy use double under pad use the good rubber one if you still have an low area or not level use a t moulding as a transaction

Call me or text me for more advice


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Thomas from Trusted Trades in Mount Forest
Date/Time4/22/2020 at 11:14:51 PM

Hey Jason,

I may have a solution for you, best explained over a phone if you have time. No sales effort, just sharing my past experience. (226)979-7549.

Would involve a simple alteration to a floor joist from below.


Tom Elliott

Renovation Specialist

Elliott's Trusted Trades Inc.

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Date/Time4/22/2020 at 11:30:20 PM


Thanks for the question. There are two main ways to fix the problem.

The first is as you mentioned, using a self leveler. You are also right to be concerned about bounding. It's hard to say for sure without seeing the condition, but if the tiles are well bonded, then you should be fine to just rough up the surface with a wire brush. It will help remove the sheen and give a better bond. Unfortunately the wetness can cause tiles that were firmly fasten to start to release so make sure to check that everything is good and solid once it dries before laying the floor.

The second option if you have access from beneath is to sister(attach a second on beside) the existing joist. You can then cut the old joist in the center, let the floor settle and screw it through into the new joist. If you go this route make sure to use the same size lumber and cover the same distance as the old one to provide the same strength.

Hope this helped,

Good luck

James Closs

Project Manager

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Jason in Brantford
Date/Time4/22/2020 at 11:34:44 PM

I have recently read about using sand to raid up the low spots they are maybe 1/4 low I'm very intrigued in that method

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Date/Time4/23/2020 at 6:43:27 AM

Hi Jason

You're right, you don't want to be ripping up though old 9 x 9 asbestos tiles. Just clean

them very well ( We're all experts on that now!) even apply floor stripper if you feel there is a build up of floor finish on the area. YES ! Floor leveling compound will work just fine ( 50 lb bag of Eze Flow ) Obviously

ensure you block off/seal any in floor heating outlets.

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Date/Time4/23/2020 at 9:21:59 AM

Hi Jason. Here's a method I used to level a 3/8" dip in a floor that I was installing 5/8" plywood on. I didn't want to rip up the existing subfloor and fix it by having to sister another joist to it. I went and got 1"/8' hardboard. I used my level to find the lowest spot, then cut a section of hardboard to to fill that area. The next section of hardboard I cut was bigger than the first to cover the first layer. and the third was bigger to cover the first 2 layers. That brought me up to 3/8" and the final 1/8" lip didn't present any issues once the 5/8" plywood was screwed down. Not sure if this would work for you with a bow instead of a dip. If it's vinyl tile that's there now, you could use wood screws & PL Premium or some other construction adhesive to secure it. Just thought I'd make the suggestion.

Good luck.

Steve Edan.

Edan Home Repair & Contracting.

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Jason in Brantford
Date/Time4/23/2020 at 8:00:35 PM

How about packing some sand down or grout or dry pack mortar

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Date/Time4/25/2020 at 8:01:02 AM

Hi Jason.

If that question is in response to my reply, I would worry about the dry pack cracking under the laminate as it was walked on. I would only use dry pack if I was putting tile over it. Probably the same concern with the sand.

I saw this item. It may work for you. Not sure where to get in Canada. You may want try

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