We're getting ready to renovate an old home (1950s) and we're adding a laundry room about 20' from edge of home. My first thought is to tunnel, but the contractors both said jackhammer. I think tunnel may be structurally better, but any opinions? For those that jackhammered, any problems with yours? It's a rebar, not a post tension slab.

SnowboardAg said:

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We're getting ready to renovate an old home (1950s) and we're adding a laundry room about 20' from edge of home. My first thought is to tunnel, but the contractors both said jackhammer. I think tunnel may be structurally better, but any opinions? For those that jackhammered, any problems with yours? It's a rebar, not a post tension slab.

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Not an engineer, but you will likely be fine with saw cutting and jack hammering. Just make sure the contractor dowels in both sides of the uncovered opening with rebar and use a high PSI mix to infill.

Tunnel unless rock
May can run along a wall to closer point before dropping down

Both great points - we have to cut to an island for electrical, and will make sure they rebar / use high psi mix. Good point on the wall. I think we could do that and cut off roughly 4-5' of tunnel. Appreciate it!

Check the labor costs for tunneling vs jack hammer. I'm guessing it's much higher but I don't know for a fact.

If you tunnel, it's difficult to get the soil compacted back into the hole when you're done. This often leads to a nice crack as the area above the hole settles. Then people call and complain to the contractor. He's trying to save himself a call-back by cutting the slab.

agnerd said:

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If you tunnel, it's difficult to get the soil compacted back into the hole when you're done. This often leads to a nice crack as the area above the hole settles. Then people call and complain to the contractor. He's trying to save himself a call-back by cutting the slab.

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I've not heard of this happening with frequency, if at all.

agnerd said:

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If you tunnel, it's difficult to get the soil compacted back into the hole when you're done. This often leads to a nice crack as the area above the hole settles. Then people call and complain to the contractor. He's trying to save himself a call-back by cutting the slab.

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I agree with this on a new slab over a poorly compacted trench. Ask me how I know

On an existing slab with a non load bearing location, not so sure.