How to install a patio that can't be properly graded?

Player

Hi, I'm going to be replacing and expanding a paver patio that wasn't installed well and looks pretty trashy. The problem is that where I need to start (at the house) and finish (at the edge of the grass) are level. I had thought about doing pavers instead of concrete so they could drain. I had also thought of doing some edging along the grass that would be level with the grass, and allow me to grade the patio just below them; but I don't want to create a tripping hazzard. I could use some informed insight here.

Thank you!

Allison1888

It's hard for me to visualize and I'm not sure of the dimensions (which will affect how much slope you need for drainage), but one thought is to create a decorative gravel/rock area near the foundation that can help with water collection. I've done this with pea gravel for most of it (about 3 feet deep and then the more expensive rocks on top to save on the cost). Instead of having a rectangle or square patio coming off of the house, carve out an oblong space against the wall for the rocks and use pavers for the rest of the wall. So, the shape of the patio would start out narrow and then curve out. Depending on the drainage issues you're facing, you could also do a rock collection area along the grass side of the patio-- same concept. Make it look decorative. Hope this makes sense. Another thought is to do a small pond, but that's a different approach.

jasoninct

what about the sides of the patio?

Does your installtion allow you to grade the patio so shed rain water to one side or the other or both?

If not you could build the drainage into the patio itself so nearly half water can drain straight down into a drainage system or drywell installed under the packed gravel base. This is labor and material intensive since it would involve removing the existing patio and the base under it followed by further excavation.

I've done a patio installation where watersheding to any side was not allowable. (patio level building entrances at all sides. I excavated the perimeter of the patio to 18 inches and all sides sloping downward tword the center (looked like an upsidedown pyramid with the top cut off). At the center of the patio the excavation was a drywell 6 feet square and 5 feet deep. The entire hole was lined with filter cloth and filled with compacted 3/4 inch crushed rock to 10 inches below grade. Above the traprock I installed 6 inches of compacted gravel, 1 inch of bedding sand and a permeable paver patio.

This installation was the entire area of a courtyard at a bbanquet facility, 1000 square feet, 25 x 40. It allowed all the storm water to drain directly through the base and into the manufactured drywell that offered enough surface area for the water to penetrate into the sandy subsoil. An engineering survey listed the installation at 1 inch of rain per hour for 6 hours before the drywell's ability to disperse water into the soil was overcome.

Player

Thank you both for the fantastic ideas! That is A LOT of digging Jasoninct. Wow!

The patio is an "L" shape; bordered on all sides but the outside of the "L". I was also thinking of extending out a little at the corner of the "L" for a table area. the depth (besides the table area) is about eight feet. In all we're looking at 600-700 sq/ft.

I was contemplating digging the dirt out and grading it away from the house. Then digging a dry well around the perimeter. Would that work?

And if I were to do something like that, how do you secure the sides of the pavers so they don't wander? I've heard of those plastic sides (with the stakes) beginning to fail in only a year or two.

jasoninct

Definately grade the patio away from the house. You don't want to be depositing storm water up against your house. as the water soaks into the soil it can create enough hydraulic pressure against the foundation to cause it to crack over time. For a patio a grade of 1/8 inch per foot will get the water to move but 1/4 inch per foot is better.

Trenching around the low ends of the patio and filling them with stone will work but over time it will start to work poorly because sand, silt and organic matter (grass clippings, leaf bits) fill in the spaces around the rocks slowing the water. You can extend the life of the percilator by lining it with filter cloth to keep the soil from getting into the rocks

Player

So you think I need to do more than just grade the soil/dirt under the pavers away from the house (so the water will dissipate through the pavers and then down the grade of the soil/dirt), I need to actually grade the pavers themselves? The only way I can possibly do that is to raise the border pavers to the level of the grass and leave a lip from the border pavers down to the patio pavers. That's why I was thinking about not grading the pavers in order to keep from having a lip, but grading the soil/dirt underneith and doing a dry trench under the border pavers. *did all that make sense?*

jasoninct

unfortunately changing the grade of the patio is going to be labor intensive.

The best way to solve a water problem is to grade the patio base so the low end is where you want the water to go. You want to make sure that there is at least 1/8 inch per foot of pitch to the base. You can do this with some wooden stakes and some string. Pick the side of the patio you want to be the high end, then choose where you want to have the low end. Measure from one side to the other to mind the distance so you can figure out how low the low end will be compared to the high end. For example, if the distance were 10 feet then the low end will be 1 1/4 inches below the high end with 1/8 inch per foot of pitch. The string is used with a string level (a special bubble level that is made to attach to a string) to establish a level line you can measure from to determine the proper pitch of the base for the patio.

The more perfect you can make the base the better the patio will look. The lines created by the bricks will make a grid pattern which makes it very easy to see any imperfections in the patio.

I would want to make sure that there is no lip on the border bricks around the patio for 2 reasons. So there is not a hazard of someone tripping on them, and so they don't interfere with water run off.

Remember there will always be some amount of water that will permeate through the gaps between the bricks. With up to 1/4 inch an hour depending on soil type, there may not be any runoff.

Player

I haven't noticed much of a water problem with the current setup...I'm just trying to figure out what to do when I replace the patio in the spring.

I'm not sure that I explained myself very well. If I grade the patio as you describe it will end up about 1" below the grass. That's why I would raise the border 1" (which is still a tripping hazard. That's why I of thinking of grading the dirt away from the house when I excavate so that the water that seeps between the pavers and through the base material will move away from the house. Would that work?

I saw some permeable pavers online, but I imagine they're pricey. Do you have any experience with them?

Player

What do you think, would that work?