What should I backfill for a slab?
The top 6 to 12 inches of the backfill under the slab should be filled and compacted with well-graded gravel or crushed material. “Walls are typically backfilled with the removed earth or with a granular, open-graded material,” says Tull.
Can you backfill with concrete?
Allow Concrete to Fully Cure before Backfilling Foundation Walls. When building a new home or home addition the question frequently comes up on how soon can I backfill foundation walls. The backfilling of foundation walls should ideally be done only after the concrete has had time to fully cure.
What kind of sand goes under concrete slab?
When pouring concrete—especially for something like a driveway—most contractors choose gravel as their subbase. The “grade” of the gravel (the size of the pebbles) depends on the project. Most local building departments have some guidelines on the grade of gravel they require for construction projects.
How soon can you backfill a concrete foundation?
7 days
The concrete must cure for a minimum of 7 days and the foundation wall must be laterally supported, meaning the floor system is installed supporting the top of the wall. All below grade waterproofing / dampproofing must be installed.
Is sand good for backfilling?
Sand is a key component of a properly backfilled hole or trench in that it provides drainage and compacts well, especially when damp. Above the rock bedding is a layer of felt to prevent the sand from washing into the rock bed, sand and top soil. Properly layering these materials prevents sinking after the backfill.
Is gravel a good backfill?
You can use sand or gravel for backfill, as both are easy to use. They both discourage weeds from growing there, and they don’t take a lot of maintenance to look great. Backfilling is the technique of filling those holes all the way in, and you can use sand, gravel, or other materials for it.
What is the best gravel to put under concrete?
Most people build a driveway or a patio so in that case, a good choice would be a mix of coarse and fine aggregate which will create a compactable base. Overall, a mix of crushed stone and stone dust is the best base material for any concrete flatwork. It all comes down to the ground and soil you will be working with.
Do you have to put sand under concrete?
As a general rule, stay away from using sand as a subbase. You’re better off using gravel; your concrete will last longer and have less of a chance of cracking over time.