new driveway, piles or dowelling in foundation?

[Cory Lechner]

We have an old driveway (28' x 8"7") that has sunk towards the house at least 6 inches. The driveway had 10 mil re-bar drilled into the house but has since then has just pulled out (or bent or broken off) as the driveway sunk.

We want to remove the driveway and replace it with new concrete.

1) Should we use concrete piles (3 to 4) or should we use thicker re-bar dowelling (3/4") "epoxied" into holes drilled into the foundation?

2) Should I have the base (1' or so) under the present driveway removed and replaced with a more stable base?

3) What type of base should be used?

4) Any ideas/comments/advice?

Cory Regina, Saskatchewan, Canada

[Randd01]

Sounds to me like the fill around your house foundation was never compacted properly and has settled over the years. If the subgrade under the concrete is done properly there is no need to dowel it in to the house. It is better off free floating to go up and down with the freeze thaw cycles. The dirt shouldn't settle any more now so if you remove the old driveway regrade the area and compact properly you won't have any more trouble.

[Randd01]

I think that would be overkill and depending on how old your house is you may not have a footing at all. If your worried about the slab settling along the foundation again you could put heavier re rod in say a #6 bar 6 ft long perpendicular to the foundation spaced every 12 inches to form 12 inch squares. Make the slab at least 6 inches thick and use a 4000 lb mix. It won't go anywhere but I don't think any of that is nessesary.