Is this an existing home that you've lived in for a while, or a new build in process?

Age of the house? Budget?

There are many old homes that have some settling. The major concern is whether or not you have structural issues.

It's possible this is minor (no structural issues) which means you remove the flooring, install a new subfloor using shims and then lay new flooring. The molding in the doorway will have to be acceptable (no toe stubbers).

If there are issues that are bigger then it could take a LOT of jacking up the house...starting in the basement or fixing the foundation, etc. It could be an easy fix or it could be very expensive.

We won't know until we know more.

We flatten every floor we do. It always needs to be flatten. Every one. We don’t say “Level” that’s a little more expensive and usually not an issue unless customer is converting a patio or garage to living space. Self leveling underlayment it the normal. Any good installer know about it and has a brand that they prefer. We use Bona SL150. Never a problem. Don’t leave your floor lumpy. Make sure to get it flat before you start.

If really bad some guys add pea gravel to take up some of the volume if really fixing a huge low. Planner on high spots works good to help that too. Watch out for the nails.

Home depot has “level quick” same stuff.

Sometimes you start at the lowest floor (e.g. basement) and start jacking up from there. Other times you go for a localized fix and level only the area you are focused on. Assume the latter in your case.

With a wood subfloor on joists, you can do one of the following:

1. Self leveling compound (SLC). Yes, can do on top of plywood/OSB with care.

2. Add thin sheets of plywood in the low areas + fill the transitions.

3. Remove floor, shim the joists, reinstall.

(I’ve never seen someone jack up a house before, but I believe you. Wow, that’s crazy. Maybe I don’t see houses that old here in San Diego)

I've seen it in some of the older homes (1900's, etc) that have settled over time (new builds in the area cause issues in the soil, etc). It isn't pretty, it isn't cheap, but when needed it works like a charm.

We still need a bit more information as to your situation (@ Rita).

I once built and installed a light metal kitchen bulkhead, carefully plumbing and leveling it to show I can actually do things, not just direct other people. It was then pointed out to me that since the rest of the room had gracefully settled off-level, my bulkhead looked off. Check that leveling your floor won't have the same effect.

Hi guys, thank you very much for all the answers.

The house is built in 1971. We just bought it and the previous owner lived there for 40 years.

We have opened one section of subfloor because we feel that part of the floor a bit squishy.

We found trace of dead termite, all dried up...I can also see an additional joist beside the old one. We figured it must be some work done by previous owner decades ago by adding one additional joist and the joist has eggs on it.

I have also attached a picture of the uneven floor, it's not noticeable much on the picture, but there is about 4mm unevenness and the corner slightly higher.

Any advice is appreciated.

If a professional is needed, do you have recommendation for Montreal, Canada area.

Thank you in advance.

Based on what you found in your one small area I would recommend pulling up the entire floor. It's easy. Check all the joists.

4mm is 5/32" which is really not much at all. You can sand high spots, fill low spots.

What's your floor covering going to be?

You need an exterminator who specializes in termites or carpenter ants. There are ways to figure out if the termite infestation is active or not (chemical analysis detects the slightly sweet smell given off by active termites).

I would put everything on hold until you tally up all the damage that was done. Your flooring budget has just gone into structurally reinforcing the second floor.

Montreal is one of our most International cities in Canada. I would be blown away if you can't find an exterminator who has this type of profile in your area.

Don't purchase anything more (ie. flooring, paint, etc) until you have this house inspected. I would also speak with your bank to determine how much money you can access to address the issue. It can take a week or two to apply for a line of credit. Right now the Bank of Canada rate is 0.25%. Lines of credit are based off of the BofC lending rate. Example:

CIBC is BofC + 3.75%

Scotia Bank is BofC + 3.25%

That's MUCH better than credit cards at 19.9%.

WOW, I didn't know you guys got termites too, I thought that was an American thing! As others have said, you need to back up, and make sure the damage isn't more extensive. At that point the leveling is easy, the floor only needs to be flat not level, so 1/4" of deflection is easy to patch.

Tear out the floor and replace the structure as required. Get a bug man.

Was a termite inspection done during the purchase process?