How to fix gap between ground and the concrete slab?

[Mo2]

 

   

Hi there

can you please advise how this gap between the ground and concrete slab can be fixed ?

Is there DIY or have to get professional assistance. 

Thanks in advance. 

[Dave-1]

Evening @Mo2 

Annoying but fixable

It looks like the soil has settled form when that drain was put in and over time it has just dropped lower. 

I would use some spare soil (not topsoil) and then a shovel at a time place it next to the hole, then using a piece of wood (something like a floorboard or a stud for a wall push the soil in as far as it can go, repeat as many times as you can and only push in small amounts until you can feel it compress firm.

Once you can push no more then I would slowly raise that dipped area with top soil, dress it lighly every few weeks and let the grass grow up through it, that way you wont have a dirty patch that needs fixing. Looking at the sewage inspection point, that should be level with your lawn so it may take awhile to build it up. You could also fill with topsoil and lay grass down over that whole dipped area. I know Bunnings stores get deliveries of grass rolls every so often. you could check your local one for when its due.

Dave

[EricL]

Hello @Mo2 

It's great that you've received excellent advice from @Dave-1. I totally agree with Dave-1's suggestions in regards to filling up the gap under the concrete. Just to add to the suggestions made, I recommend doing a bit of investigation and having a look at the flow of water in that area during a heavy downpour. 

I suspect that water is somehow finding a way underneath that concrete slab and slowly eroding the soil away. If you do find water flowing underneath, that issue will need to be addressed in order to prevent further soil erosion.

If you need further assistance, please let us know.

Eric

[Mo2]

Thanks guys for the quick response. 

Is there some sort of expandable foam that can be of any use here?

Seen some youtube videos where they inject the foam in concrete by doing holes and then inflate the foam. 

Thanks again for assistance 

[Dave-1]

Evening @Mo2 

I have seen that expanding foam and it looks pretty good.  Tho from what I have been able to find out it is expensive, potentially in the realm of what a new section of path would cost to put in.  

Apart from that I am a little questionable about the enviromental cost/impact using the foam, It looks like it would do a good job but how long would the foam last (years? decades? longer?) I actually think my pool has had that used in the slabs around it as I have these stainless screws in the concrete and cant work out why unless its the foam. Tho not willing to dig it up to find out lol

Does your slab have cracks in it? I like @EricL's thoughts on the water going somewhere, it would prob be wise to check it out, maybe fill the area with a gentle hose and then see if there are runs in the water towards the slab?

Dave

[Mo2]

Hi. 

I think you are right. Water is going from these gaps between the slabs and over the years it has compacted the soil. 

Caulking on these edges could be helpful after filling the bottom gap with soil ?

I have cleaned this are but the weed actually make its way from these gaps so assuming water is making the way from here 

[JacobZ]

Hi @Mo2,

Thanks for those additional photos.

I would suggest that a combination of water flowing through the crack and settlement from when the drain was installed are to blame for the erosion.

Filling the crack with Sika 11FC will help to stop water flowing down through the crack and eroding the soil further. Once this crack is filled, I would build the soil up from underneath like @Dave-1 has suggested, compacting it as best you can before bringing the surrounding area up using topsoil.

If you find that the soil continues to settle, there may be a small leak in the drainpipe that is causing the soil to erode away. If you find this is the case, you may need to contact a plumber to fix the cracked drain pipe.

Let me know if you have further questions.

Jacob

[Mo2]

Hello. It’s me again. 

 

Do you guys refer any soil product I can get to fill up underneath the concrete slab? I am after sometime that comes up in bags for ease ?

Thanks guys. 

[JacobZ]

Hi @Mo2,

Welcome back, it's good to hear from you.

I'd suggest using a combination of drainage gravel such as Ki-Carma 20kg 10-20mm Drainage Gravel and a garden soil mix such as Scotts Lawn Builder 25L Organic Lawn Soil Topdress & Underlay. 

The drainage gravel can be used to backfill and compact underneath the slab, and the top-dress can be applied over the grass to bring the level of the earth up to the bottom of the slab.

Let me know if you have any further questions.

Jacob