Concrete slab needs proper base material – Sun, 15 Feb 2015 PST

DEAR TIM: What type of stone would be best for filling a cavity under a planned two-car garage addition? It is approximately 7 feet deep. The local concrete supplier sells recycled concrete for a really good price. Due to the design, compacting will be next to impossible. Whatever is used needs to be self-compacting. Do I have options? What else would you do to ensure the concrete slab that will be poured on top of the fill will not crack or settle? Dave L., Knoxville,Tennessee

DEAR DAVE: I know what youre thinking. That low price on the recycled

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DEAR TIM: What type of stone would be best for filling a cavity under a planned two-car garage addition? It is approximately 7 feet deep. The local concrete supplier sells recycled concrete for a really good price. Due to the design, compacting will be next to impossible. Whatever is used needs to be self-compacting. Do I have options? What else would you do to ensure the concrete slab that will be poured on top of the fill will not crack or settle? Dave L., Knoxville,Tennessee

DEAR DAVE: I know what youre thinking. That low price on the recycled concrete is whispering in your ear. Its a great product for many things, but based on your description, Id not useit.

I have built custom homes that had attached garages that needed fill around the foundations and under the slabs. I also built garage additions very similar to yours. Because Id had to go in and repair many a sunken garage slab put in by some builder or remodeler cutting corners, I quickly realized that garage slabs can and will fail horribly if you dont put in solid, compacted fill underthem.

I always use washed peagravel.

The recycled concrete does compact well using rollers or plate compactors, but as you said, thats very tough to do in your case. To get full compaction, you need to do it in lifts where the material being compacted is not much more than 4 inchesthick.

Some gravel companies have special dump trucks outfitted with conveyor belt delivery systems. This tool swings side to side and up and down much like the digging arm of a backhoe. The driver can shoot tons of pea gravel into your foundation in minutes, saving you hours of back-breaking labor shoveling andhauling.

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Concrete slab needs proper base material - Sun, 15 Feb 2015 PST