Concrete Experts - Need Advice

The owner of this condo here in Vancouver didn’t like his patio - so he had a new 1.5" topping poured over the old.

I can see he correctly used a bond breaker, and notched the drain to permit drainage from between the two pieces.

My concerns:

  1. When I tapped it, there was a hollow area near the base of the door. I believe he may have poured the topper over pavers sitting on the soil. Settlement? Will it eventually crack?

  2. He’s buried the metal flashing near the house (see photos). What will happen to this flashing over the long term?

Thanks for any help!

PS: Photo #1 shows neighbouring unit which is how his looked before.

if the pavers were left in place you are correct they will shift, settle, move and this will eventually be seen through the concrete.

Typically the concrete will carry the crack between the pavers to the surface.

Metal flashing that is present will eventually rust and deteriorate.

There should have been an expansion board placed between the exterior wall and the concrete pad. This would allow the concrete to swell and contract without pressing directly on the wall.

Thanks John, that was exactly the kind of advice I was looking for! I wouldn’t have caught the expansion issue.

To correct the issue will the owner need to cut back on the pad and add the expansion board?

Not sure that an expansion joint is needed at the wall. That pour is not really large enough for that, and it is open on two sides…should be sealed at that connection for water intrusion though. The dissimilar base layer (pavers, if present) for the toping coat may crack at that joint in the future. Looks like a fairly professional install that may or may not have a problem with cracking. I would just note the condition and defer to the warranty from the contractor.

Trying to add an expansion at this point would do more damage to the aesthetics than good. Seal the flashing area.

Thanks Bradley. I feel like it’s a professional quality job, just concerned about the flashings.

John/Bradley - What type of sealant is recommended for this application? Polyurethane?

Concrete needs 4" in depth to be long lasting.
Any concrete underneath has to have it’s surface cleaned.
I would mechanically rough the surface and add a latex adhesive.
Another method, applied concrete over the top. 4" was the thinnest area with some depth reach 5 or 6 inches. No surface is flat.
The top cleaned of any geese or oil and organic materials. I used a commercial pressure washer.
Then anchorage placed every 24 square. Atop would be 4’ rust resistant metal lattice.
I spaced the anchorage every 24" and raised the lattice 1.5 inches off the surface.
The 1.5 inch coating will spall eventually. They do the same thin coating with swimming pool patois.
My last inspect had a 1/4 to 1/2" coat over unit pavers.
They did not get one year out of it before the pavers started to show through I bet.

The purchaser did not listen to me tell him the entire lot is reversed. I suspected 100,000 in possible issues. I was right.

Yes, polyurethane caulk is good - Vulkem 116

Question, does it look like professional job, or it is a improper proper technique.

Laterally pored Concrete slab damage, as in a walk or driveway, are due to several factors. Erosion being the underlying factor, correct?
How did you determine in a non destructive manner to the concrete and observe what lay underneath the old concrete.
More to the point, was the substructure, soil, sloped in the right direction,away from a foundation, pier or footing and was there 2 to 4" inches of clean aggregate underneath the old slab?

Lets look at two concrete erosion probabilities. Uplift and torsion.
A flat rigid surface being lifted up and not in a uniform manner. It is twisted.
Question, Will a 1.5" inches thick slab of concrete not bonded properly have the same rigidity as a 4" slab when it is placed under stress.

I would be looking for; What was in the proximity of the slab? Trees, what type and how big. Any bushes or plantings. Automatic sprinkler system,. Is the any potability of soil heaving. Was the old slab sinking and that is why a new slab was placed on top?
Any downspouts or other water sources that could allow a stream of water to penetrate the slab at grade.

Again I will ask you a question. Did it look like a professional job or was it the proper technique?

If the old slab was broken, then adding more wight on top will make it do what?
Await a reply.

Update: Received the following email from the owner, who himself is a concrete contractor:

I have attached photos related to the installation of a 1.5" thick decorative concrete topping onto the existing concrete patio in front of my unit. A uniform concrete thickness of 1.5 inches was added and sloped in accordance with the existing 6" thick concrete base slab. The entire patio area is sloped towards the existing drain. Polyethylene sheeting was used between the existing, and topping slabs. The bottom side of the drain pipe was notched (photo #6) to provide drainage for any moisture which may accumulate between the concrete topping and base slabs. All pour heights are bellow the existing flashing as to prevent moisture from flowing back towards the building. Concrete used was 35MPA with 5-7% air entrainment (required for all exterior concrete structures).

He states “All pour heights are below existing flashing” but that is not the case, as you can see in the OP…

Decorative concrete. That should have been noted from the start.
As for flashing… what component is flashed and what material was used?
All the best.
Question… if the owner is a concrete expert, then why ask you?

In image number 3, caulk the intersection.

Thank you Robert!

David, be wary of decorative finishes. A band aid effect is usually the case.:mad:
Insure the word decorative is boldly implied in your report.
Too pour a good slab takes preparation and is not cheep in my neck of the woods buddy.
Just to remove the old slab would be 1,500 plus easy!

RECOMMEND: A small hand tool to dig 10 inches below grade to see the slab, foundations and other below grade finishes.:wink:

Do not get caught with your pants down David.:roll:
Heads up buddy or refer it out and let someone else hold the hot potato.

All the best David.

I agree with all of this advice except the need for an expansion joint. On a small pad like this you are not going need it. My immediate concern would be the condition of the ground that the slab was poured on. If paving stones were left in lace it could lead to problems down the road. You should always ensure a clear and well prepared ground for pouring concrete. Especially in Vancouver where the rain can cause problems with water build up and cracking if proper drainage isn’t put down.