Walkout Patio

[mark2424]

Hey everyone, wondering if someone would be able to help me. I have a walkout stamped concrete patio that has frost heaved about 4 inches at the front. It used to lift the deck up but I saw cut around the post and now the deck is fine but I want to install a proper fix. I just wanted to get peoples take on how to remedy the issue, I have heard of possible fixes by Jackhammering the patio then digging down 18 inches and repouring over 4" of foam.

I was just wondering if I get away with doing a french drain(with weeping tile) with a gradual slope in front of the patio and tie into the weeping tile around the foundation... not sure if that would be a waste of time or not. My neighbours house didn't heave... I am also in Edmonton. We also have fake grass and OK drainage in the backyard but not great.

Thanks,

Mark

[Map Maker]

Just a guess on limited amount of info.
But I don’t think it’s ground frost heave (because your deck post doesn’t move)
I think your problem is water pooling under the patio and freezing and lifting.
Either they poured over topsoil or didn’t grade correctly.
I would try like you said and dig deep right in front and try to dig under the patio.
Install weeping tile and get the drainage out and away.

[FCLightning]

The place I worked at had that problem with the slab in front of the entry. The problem was a high water table. Digging down and pouring over sand and styrofoam did nothing to solve the problem. Then they dug it out a second time and installed weeping tile to a sump and got rid of teh concrete altogether. The guard posts on either side of the loading doors have developed a considerable lean to them and the outswinging man door needs to have the gravel chipped away from in front of it every winter. Freezing water is a powerful force and if you don't get rid of the water you won't get rid of the problem.

[EZM]

Just a guess on limited amount of info.
But I don’t think it’s ground frost heave (because your deck post doesn’t move)
I think your problem is water pooling under the patio and freezing and lifting.
Either they poured over topsoil or didn’t grade correctly.
I would try like you said and dig deep right in front and try to dig under the patio.
Install weeping tile and get the drainage out and away.

If the post is below the frost line it's far less likely to move.

If the patio isn't (and they are not unless they are piled) they will move under any frost load.

[EZM]

Hey everyone, wondering if someone would be able to help me. I have a walkout stamped concrete patio that has frost heaved about 4 inches at the front. It used to lift the deck up but I saw cut around the post and now the deck is fine but I want to install a proper fix. I just wanted to get peoples take on how to remedy the issue, I have heard of possible fixes by Jackhammering the patio then digging down 18 inches and repouring over 4" of foam.

I was just wondering if I get away with doing a french drain(with weeping tile) with a gradual slope in front of the patio and tie into the weeping tile around the foundation... not sure if that would be a waste of time or not. My neighbours house didn't heave... I am also in Edmonton. We also have fake grass and OK drainage in the backyard but not great.

Thanks,

Mark

Frost heave is most likely the issue - so even with a compacted subbase properly done, unless it's evacuating all the water from the sub-base, you will get movement under frost. In other words, your 20mm crush sub base could have been dug down into clay and water is saturating your subbase and when it freezes, it moves.

The fact that your post doesn't move but your slab does, (assuming it's below frost line), is a dead give away here.

All sub-bases need to be able to "wick" the water down through and away from where it makes contact to the poured slab. If the water has nowhere to go it doesn't matter what you do here. So before jack hammering have a look at it and around it to see if there is a negative pitch, or something else that is collecting moisture.

A proper foam insulation layer will provide some "movement" to be absorbed, ands helps prevent (reduce) frost heaving but it's not 100% fool proof - particularly when there's enough water to saturate up to the foam and come up over the edge/through the seams - then you are back to square one - a little better off, but still not totally safe.

If you can get the water to evacuate (relive) the area under the slab without removing it, that's your best bet. There are options once the ground frost comes out to do this (as long as you have the pitch/drainage to do it on your property there.