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allangee t1_jeazn3l wrote

It sounds like you have a poured sidewalk (otherwise you would have just lifted a block). Very likely it's reinforced with rebar and/or steel mesh. That means it'll bridge gaps well.

I'm guessing you're going to put in a 4", maybe 6" pipe to accommodate the downspout outflow. If you keep your excavation close to the width of the pipe, the concrete will bridge that without back filling so that should ease your mind a bit.

But I know where you're coming from... I feel the same way about these kind of projects.

Depending on your access, and how wide the sidewalk is, you could mix a "soupy" batch of Quikcrete and let it free flow in, in layers. If one end is higher than the other, you'd obviously start there and block the other end as the concrete rises.

If that's not possible, poke in as much coarse gravel as you can (jagged stuff, not pebbly). Then run water through with sand to fill up the gaps.

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Kalarix OP t1_jeazvi0 wrote

Correct, it it's a poured sidewalk and a 4" drainage line. Thanks for the reassurance and recommendation.

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allangee t1_jeb0a6k wrote

Depending on your soil conditions, you can possibly notch the end of 4" pipe and twist/drill it through under the walk, sucking sand/gravel out with a shop vac.

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Kalarix OP t1_jeb1xnv wrote

I can hope they put a decent base down under it, but other areas I've hit clay pretty early unfortunately

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