Greenhouse Drainage: Will this solution work?

[BrassavolaStars]

Hello all,

As you all know by now I am making a paver floor in my GH and one concern that was brought to my attention was getting proper drainage. My question is will this solution work?

Buying one of these and putting it in the back corner, https://www.lowes.com/pd/NDS-6-in-L-...E&gclsrc=aw.ds

Having it go a few inches under the base using a downward PVC pipe and an elbow to go outside, and finally routing the water to another section of yard using these with gravel Access Denied

Will this work?

Are the channel drains better? Keep in mind, I am only dealing with at the very most 16 gallons of water a week in an 8x12 structure that slopes down slightly at the 12 foot side.

Is there a simpler or easier solution? What is my best and most efficient option.

Thank you.

---------- Post added at 01:36 AM ---------- Previous post was at 01:07 AM ----------

Additional question: If I do get pipes that take the water out of the GH, do they have to be buried “below” the gravel I am laying for my pavers or can it be buried within the item 4 gravel. I ask this because my item 4 will be already significantly below grade level and I am not sure I could dig another 6 inches down below where I intend to put the item 4 to cover a 4 inch pipe and still be able to have it slope adequately.

[DirtyCoconuts]

it should work fine.

i don't see the down side of digging it down for better results (as in below the gravel) but as long as the drain is at the lowest point in the greenhouse it will still direct the water out.

i don't think you need the drain piece at all as the water will get through the pavers and the gravel easily and you just need to get it out of the greenhouse

[Ray]

I don’t think that’s your best option. Certainly it will work, if that corner is the lowest point on the floor, but you will have to dig deeper, to accommodate that drain, the elbow and the drain pipe, which should be sloping down as it leaves the structure. I would guess that the drain and elbow (even using the smaller 3” pvc option) will be at least 6”-7” top to bottom, and the drain has to be recessed slightly in the floor. That also begs the question “where does the water go?”.

Because you’re adding the pavers after the structure is in place, I think you’re either going to have to do some serious excavation or go with a less-perfect solution that achieves the goal.

This may sound odd, but one simple method would be to run a few short lengths of 3/4” pvc pipe just under the foundation on the lowest side. (Put screens over both ends.). When you add the gravel, have it come up at least as high as the pipes, so the pavers are above them. Don’t use the sand. (I know you said it has been paid for and isn’t returnable, but that doesn’t mean you have to use it.)

The gravel bed becomes your sump and the pipes are your overflow to prevent flooding.

Of course, this all may be a waste of mental effort. A gallon is 231 cubic inches, so if you assume 20% open volume in the gravel and a full spillage of 15 gallons, your sump would have to be 231 x 15 x 5 = 17,325 cubic inches volume. I don’t recall if you ever mentioned the size of the structure, but if it was 8’x10’, the gravel would only need to be 1.5” deep!

[BrassavolaStars]

Originally Posted by Ray

I don’t think that’s your best option. Certainly it will work, if that corner is the lowest point on the floor, but you will have to dig deeper, to accommodate that drain, the elbow and the drain pipe, which should be sloping down as it leaves the structure. I would guess that the drain and elbow (even using the smaller 3” pvc option) will be at least 6”-7” top to bottom, and the drain has to be recessed slightly in the floor. That also begs the question “where does the water go?”.

Because you’re adding the pavers after the structure is in place, I think you’re either going to have to do some serious excavation or go with a less-perfect solution that achieves the goal.

This may sound odd, but one simple method would be to run a few short lengths of 3/4” pvc pipe just under the foundation on the lowest side. (Put screens over both ends.). When you add the gravel, have it come up at least as high as the pipes, so the pavers are above them. Don’t use the sand. (I know you said it has been paid for and isn’t returnable, but that doesn’t mean you have to use it.)

The gravel bed becomes your sump and the pipes are your overflow to prevent flooding.

Of course, this all may be a waste of mental effort. A gallon is 231 cubic inches, so if you assume 20% open volume in the gravel and a full spillage of 15 gallons, your sump would have to be 231 x 15 x 5 = 17,325 cubic inches volume. I don’t recall if you ever mentioned the size of the structure, but if it was 8’x10’, the gravel would only need to be 1.5” deep!

The structure is 8x12 and the gravel will be 3 inches deep. To be fair though, it isn’t straight gravel but recycled crushed stone and brick which includes both large and small particles. It is called item 4.

[Ray]

Originally Posted by BrassavolaStars

The structure is 8x12 and the gravel will be 3 inches deep. To be fair though, it isn’t straight gravel but recycled crushed stone and brick which includes both large and small particles. It is called item 4.

So 96 x 144 x 3 = is 41,472 cubic inches. If we assume the porosity is only 10% (it's probably much more), we're still looking at a holding capacity of almost 18 gallons.

I still think adding the sand layer is a mistake, though. Pavers on top of the tamped-down "item 4" is your best bet.

My greenhouse in PA was built on a hillside. The right front was 1' above grade, while the left rear was 5' above grade. I filled the foundation with "scrap fill" - a combination of gravel, soil and chopped up tree trunk/root balls (10% the cost of gravel) to within a foot of the top, then filled the rest with gravel. No pavers, no blocks, nothing. Worked great as the floor, but I did put cement pavers under the bench legs.

[WaterWitchin]

I'm with Ray. Sixteen or so gallons of water is nothing. And it won't ALL be going to ground unless you spill it. Three inches of gravel, done. Especially with the pavers you've chosen. Slight slope toward lowest end of greenhouse. You can always dig out and backfill on low outside perimeter with sand if needed, but doubtful you'll need to... unless you have a lot of water on high side of greenhouse that's somehow perking into the greenhouse itself. In that event, you'd need a french drain on high side.

[Fairorchids]

I agree that drain to outside is not necessary. However, having laid my share of pavers: You can't eliminate the sand, as you can't level pavers laid directly on aggregate.

Solution might be to add a layer of fabric (weed blocker?) between aggregate and sand, so that the sand doesn't wash into the aggregate.

[BrassavolaStars]

Originally Posted by Fairorchids

I agree that drain to outside is not necessary. However, having laid my share of pavers: You can't eliminate the sand, as you can't level pavers laid directly on aggregate.

Solution might be to add a layer of fabric (weed blocker?) between aggregate and sand, so that the sand doesn't wash into the aggregate.

This is my current plan. I have been working from the graphic you sent me a while ago. I will post pictures soon I am about to lay the gravel. My plants have been outside when it has gotten down to 46f and thankfully even the Phals are fine.

[WaterWitchin]

Yes, as Kim says... Or lay a geotextile between gravel and sand. Either works. I keep forgetting there's no chat over the gravel.

[Ray]

Originally Posted by Fairorchids

I agree that drain to outside is not necessary. However, having laid my share of pavers: You can't eliminate the sand, as you can't level pavers laid directly on aggregate.

I disagree.

When we redid the landscaping of our front yard in PA, I dug a long, winding trench about 8” deep x 4’ wide for a paver walkway. It expanded to 6’ wide as you approached the front door. I put about 6” of gravel and leveled it with a screed, then used a power tamper to pack it. With a few add/level/tamp repetitions, the gravel was quite level and the brick pavers went right on top.

I did apply sand in between, and it stayed tight and level for about 15 years before we moved.

Water ran off, not through the sand, so that’s what makes me suggest against it.

Putting pavers down for walkways and using them for flooring where drainage is required is not the same thing.