Dryer vent through cinder block and then through yard - is this ok?

Question

I've been researching how to vent my basement dryer, using galvanized steel ducts. There are lots of things on Google that show how to do this under a normal situation, but mine is unique, and I can't find a good answer yet.

Normally one would drill a hole through the wall that faces the outdoors, and run the duct through there. But I can't because my walls to my house are stone, and I would never want to drill a 4 1/4" hole through it.

Instead, I'd like to dig a hole in the yard, where the vent will come through the basement cinder block, and then drill through the underground cinder block. This requires three 90 degree turns, but the total equation is less than 25' (counting 5' for each turn).

Is this ok (I follow Maryland code)? Will the weight of the dirt harm the steel duct when I refill the ground around the vertical duct? And which kind of cap should I use at the end (assuming this is ok to do in the first place)?

Hopefully this picture helps:

Answer 1

You can get duct that is rated for underground use. It's more expensive of course, usually stainless steel.

Your MUCH bigger problem with this idea however is that you are introducing a place for ground water to enter your basement. There is no good way to seal something as large and flimsy as vent pipe penetrating a basement cinder block wall. This will result in a long term nightmare that will be very difficult and expensive to fix. The only possibility I can think of is to use cast iron pipe, like a sewer pipe, with an approved wall penetration method and all joints sealed against water leaking IN to the pipe and thereby into your basement. Making your dryer vent connect to the cast iron pipe may be a challenge, but creativity should win out.

But rather than that, I would call a "concrete coring company" as ask about them coring a hole for you in the stone wall. It's done all the time.

Answer 2

You can do what you are suggesting. I like the bore through the stone better though.

If you want your method I'd use a plastic pipe as a sleeve or a corrugated metal, parge/concrete around the sleeve, run your underground rated sheet metal through the sleeve, parge/caulk between the sleeve and your sheet metal (you might want a fire rated caulk), then depending on your foundation wall you might want to use a fiber tape meant for foundation cracks, embed it with a foundation coating and put it around your sleeve/sheet metal penetration, further you could put a dimple board and blue skin the dimpleboard back to the sheet metal. Backfill after that. I am not sure what kind of cap to use once you penetrate the surface though.

I did something similar for air input as an earth tube but I used hdpe pipe 6" ID. It is 8' underground, comes through my poured foundation, is blue skinned and dimpled boarded on the outside. No water comes in.

A lot of work though so I'd go with coring the stone as a first pass.