The slab should not sound like it is hollow under it or that it is thin at that point.
Pour concrete over old slab.
The condition of the existing slab is the primary factor that determines how long the new concrete will last.
The slab in this situation is over 40 years old and if it is stable then good results might occur on the other hand you can t really tell by looking at it.
A well poured concrete slab with a deep sturdy foundation can last for 30 to 40 years.
Concrete repair guide aci 546 and guide for concrete floor and slab construction aci 302 1.
When wouldn t i want to pour new concrete over old concrete.
If you re concrete has large cracks and the slab may still be moving due to freeze and thaw conditions or settling then a tear out and replace is a better solution.
Pouring concrete over old concrete instead of directly over a new gravel foundation limits your ability to maximize the slab s lifespan.
In the video below i poured a new stamped concrete patio slab right over the old existing concrete.
It was originally poured in multiple sections so it had some seams that looked like cracks.
One way is to tap on the slab around any cracks and then in a good area.
Make sure the braces are level and lay down a barrier of wire mesh over the existing concrete inside of the barrier.
A well poured concrete slab with a deep sturdy foundation can last for 30 to 40 years.
How to pour a concrete slab.
The surface was badly worn and pitted but the slab was sound and there was ample height to pour a new slab right.
The old concrete was over 20 years old.
Pouring concrete over old concrete instead of directly over a new gravel foundation limits your ability to maximize the slab s lifespan.
There are cases when pouring new concrete over old just isn t a viable solution.
You ll find a lot of useful information in two aci reports.
The condition of the existing slab is the primary factor that determines how long the new concrete will last.
It is possible that you may have to remove the existing slab prepare the supporting subbase properly and then pour a new slab to achieve the results you desire.
To lay new concrete sweep and clean the old concrete and saturate the old concrete with water.
Then build a perimeter or a wood brace that is the same height as you want the concrete to be.