Shower Floor Repair - Help!

[RandomRando]

Hey folks. So i recently joined the homeowners club.

The ensuite bathroom looked to have a recessed drain when we went through the place prior to OTP. Figured no biggie, we'll redo the bathroom anyways at some point, so fixing the drain wont be a hassle. Being a tradesman, i had a sense of (false) confidence i could get it done easily enough and get the shower operational.

So today, i went at it... and found the drain is recessed indeed, with a hollow cavity below it. Initially, i thought this cavity was from some degree of washaway, but i could fill it with a slurry, reset the drain and retile the shower floor. Presto, shower fixed and off we go to the next item. Ha. Ja, right.

Upon closer inspection (removing the drain pipe, and chipping away at the floor) to understand how big the cavity is for filling, i have discovered it is huge. Im not sure if this is meant to be like this??

The shower floor seems to have been raised at some point(~50mm), although the slab below it seems much stronger. The raised section seems more like compressed building sand, not concrete, atop which had the tiles. The section to the right of the hole sounds hollow when tapped whereas to the left sounds solid.

Below the slab is the issue. There is a gap of about 100mm between the underneath of the slab and the ground. Is this right? How do i fix the hole in my shower floor with this cavity being so large? Is the slab effecrtively not meant to sit flush on the ground? This cavity extends as far as i can see around the hole in the floor, at least a 2 or 3m radius.

What do i do here? Is this normal, is it a huge problem or not? How can i fix the hole in my shower floor so i can reset the drain, retile and be able to use my shower?

TiA!

 

[RandomRando]

If you're wonderful about the outside wall: the galvanized pipes sprung a leak and the old owner had contractors chip the wall open to find it and replace the rotten pipe. I do intend to scrape this area, replaster where needed and repaint the whole house. But that picture is to indicate the house design regarding the FGL and slab etc. (Incase necessary)

 

[RedViking]

Eish... I would give some input in what all I think is wrong there... but my brain is fried tonight. First impression is there used to be a timber floor and they later filled it up and then poured the slab on top. Definitely a problem as nothing is supporting the slab. Also, where is the dam proofing under the slab. The moisture from the ground is going to (and has been) a nightmare.

the galvanized pipes sprung a leak and the old owner had contractors chip the wall open to find it and replace the rotten pipe

Now to get the true story from them

Can you get hold of previous backdated plans of the house?

 

[Gielie01]

Im no expert


But this photo tells me the concrete and sand touched at some point, as youd expect when casting a concrete slab, it has either sunken away or it was never properly compacted prior to casting the concrete.

In my mind thats a problem as it also seems the floor has a slightly uneven thickness, I can see some of the rebar poking out in spots. If it was me, id chop it up ensure that spot is compacted properly and pour new concrete, a PITA for sure.

Its possible that it leaked for many years and caused the "erosion" or "compacting".

But im no professional, just a DIY Enthusiast that knows enough to get myself into k#k.

 

[Katelknaap]

Im no expert

View attachment 1686347
But this photo tells me the concrete and sand touched at some point, as youd expect when casting a concrete slab, it has either sunken away or it was never properly compacted prior to casting the concrete.

In my mind thats a problem as it also seems the floor has a slightly uneven thickness, I can see some of the rebar poking out in spots. If it was me, id chop it up ensure that spot is compacted properly and pour new concrete, a PITA for sure.

Its possible that it leaked for many years and caused the "erosion" or "compacting".

But im no professional, just a DIY Enthusiast that knows enough to get myself into k#k.

This sounds about right. The original fill below the floor slab has settled over the years. Judging from that outside photo it has extensive fill as the floor level is quite "high". The bad news is, if it looks like this here, it will could have settled elsewhere through the house as well.

 

[Bliksis]

Man am I glad I never wanted a "project" house.

 

[soulie]

.

 

[soulie]

youve got some serious erosion there ,compact ,fill with crusher compact and concrete .but get a builder in first to assess the foundations and stability

 

[RandomRando]

Eish... I would give some input in what all I think is wrong there... but my brain is fried tonight. First impression is there used to be a timber floor and they later filled it up and then poured the slab on top. Definitely a problem as nothing is supporting the slab. Also, where is the dam proofing under the slab. The moisture from the ground is going to (and has been) a nightmare.

Now to get the true story from them

Can you get hold of previous backdated plans of the house?

I have them, will give them a closer study in the morning

 

[RandomRando]

This sounds about right. The original fill below the floor slab has settled over the years. Judging from that outside photo it has extensive fill as the floor level is quite "high". The bad news is, if it looks like this here, it will could have settled elsewhere through the house as well.

This is also what i suspected was the case. Water erosion from a shower drain wouldn't do this on such a large scale, i don't think.

So then, the question becomes, how bad of a risk is this and how does one fix it? Pump slurry into the cavity until its full? How does one even do that. Or literally start pulling up the floors as suggested?!

 

[RandomRando]

youve got some serious erosion there ,compact ,fill with crusher compact and concrete .but get a builder in first to assess the foundations and stability

That means pulling up the floor, which means checking other rooms too? I.e: large pilot holes?

 

[soulie]

That means pulling up the floor, which means checking other rooms too? I.e: large pilot holes?

dont do anything before youve consulted with a builder ,they can maybe sound for cavities .stability is foremost now .the outside wall take the plaster off and drill a few holes in brick joints to aid evaporation,you may ,probably find its only one spot

 

[Mannydefreitas]

That entire bathroom needs a redo.

 

[RedViking]

That entire bathroom needs a redo.

@purple face , is this you?

 

[maumau]

Isn't that a latent defect? Could you get your money back?

 

[SauRoNZA]

Who on earth put laminate floors like those in the bathroom.

 

[Jean Claude Vaaldamme]

If you look at a house and you just get a hint of damp problems, walk away.

 

[purple face]

@purple face , is this you?

No sorry not me

 

[B-1]

This is also what i suspected was the case. Water erosion from a shower drain wouldn't do this on such a large scale, i don't think.

So then, the question becomes, how bad of a risk is this and how does one fix it? Pump slurry into the cavity until its full? How does one even do that. Or literally start pulling up the floors as suggested?!

Best bet is to get an engineer out for advice. Might not be the cheapest but they can give you a few options.

If one of them is to fill the cavity with concrete then you would typically use a vibrator to distribute the slurry. The issue then is that there is still no dampcourse.

To be honest some labourers who know how to work a jack hammer could rip out that floor in a few hours and fill and compact in a few more. Then cast the slab the following day.

 

[SauRoNZA]

Isn't that a latent defect? Could you get your money back?

Likely accepted it as a known issue.

Latent defects are purposely hidden ones.