Fill trenches with slurry to avoid sink

After digging a trench through a concrete-covered area, fill it back up not with dirt but with a slurry of Portland cement and sand.

Slurry after escavation

My name is Jerry F. I live in Santa Clarita and I’m not sure if you’ve ever answered questions on commercial properties.

 I’m hoping you can help me on this, it’s not a big deal, but I have a concern. 

I have the cable company who wants to go onto my property and trench about 18 inches wide, going back about 150 feet. 

My concern is that any time I’ve seen this being done, they cut the concrete open, due what they have to do and after everything is put back and time passes, you see this 18” wide concrete area sinking. 

This is the last thing I want to have happen on my property. How do I ensure that this wouldn’t happen here? 

They’re asking me permission and I’d like to oblige but I also need to protect the property. I’m a computer guy and don’t understand a lot about construction, so looking to you for guidance.

Jerry F.


It’s simple. When they do their excavation, depending on what they’re spec’d out at, they’ll go down 18 to 24 inches for their dig. 

Once they install their cables then it is time for the important part. You don’t want them putting the dirt back. You want them to slurry the excavated area. 

Slurry is typically a 6-sack mix of Portland cement and sand, which is the equivalent of 90% compaction, if you were to use a compactor. 

This will ensure that there won’t be any sinking. The other thing that can be done but with this slurry mix generally isn’t, is that they can add some rebar. 

If it is a bargaining chip for you to get this done, you can ask that every 24 inches a piece of rebar be installed into the existing concrete on either side, and this will be extra insurance. You truly won’t need this with the slurry, but if you feel better, then request it. When they do this, they’ll leave it about 4 inches from fill, let it set up for a week and then they’ll come back and finish the concrete. 

This method will give you a good finished area that will not sink. Good luck on this.


Tiling above the threshold

I live in Canyon Country and recently had some tile put down onto my second floor deck. This was about a month ago. 

I have plants up there and water them, and wash down and now I’m seeing wet spots in my living room. 

I called the tile contractor back and he said it’s not from his work. 

I’ve sent you photos, about 20 with close ups, can you tell what is causing this? 

Ilene F.


It’s very clear what is causing this. 

Thank you for the many photos. They tell the story completely. 

The tile has been set atop the deck and now the height of it is above the threshold. So it is acting like a pocket or funnel, and the water is traveling via the path of least resistance, heading to your living room. 

First things first, if this area is wet enough, it needs to be dried out to prevent mold. Opening the drywall may be necessary, and until this problem is fixed, no more washing down on that new tile. 

Definitely get this fixed prior to the rains, as you’ll end up with a mess inside your home. 

Bring the tile contractor back out. He is the central cause of this. 

The tile should have never been put higher than the threshold, and truthfully it should have never been put onto the decking system. The decking system needs to breath, and if it is worn and in need of an aesthetic improvement, then it should have been redone instead of having tile put onto it. 

Keep in mind the weight added to the deck also. You may be compromising the structural integrity, if it is too much weight for how the deck was engineered. 

Do yourself a favor, remove the tile and redo the decking system, you’ll be much happier without the worry/water intrusion issues. Good luck.


Robert Lamoureux has 38 years of experience as a general contractor, with separate licenses in electrical and plumbing contracting. He owns IMS Construction Inc. in Valencia. His opinions are his own, not necessarily those of The Signal. Opinions expressed in this column are not meant to replace the recommendations of a qualified contractor after that contractor has made a thorough visual inspection. Email questions to Robert at [email protected].

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