View Full Version : Raised planting Bed on Blacktop
08-22-2006, 10:39 PM
:dizzy: Hello.......I am new to the site, so bear with me. Need some advice on building a raised planting bed "directly on top of a blacktopped surface". A job I am bidding on is required to have 20% of their property "green space"- per village ordinance (business). They need (2) raised planting beds, with misc shrubs/perennials in the front of their business........on top of the parking lot. they are not required to tear out the blacktop. I was thinking layer of gravel, with some drainage piping (perforated) before dirt added, and placing landscaping blocks around.........besides drainage issue and soil runoff, I think my biggest problem will be making the wall level....due to the uneven parking lot, and not being able to "sink" that first stone in the ground. The wall (bed) w:dizzy: will be (3) blocks high with a capper on top. Any suggestions? :cry:
08-23-2006, 12:19 AM
First, nothing is ever as simple as it seems. See "rotors wont work" and "lights at the end of the line too dim" as a couple of examples.
You will need to cut out the spot for the planters if for no other reason than for the footing for the wall. Make the footing level and the wall will be level too. As far as drainage you have two options cut out all the asphalt and let the planters drain right there. Although I would be concerned about moisture getting under the asphalt, wicking out, and causing the asphalt around the planter to deteriorate.
I would only cut out for my footings and fill any gaps inside with concrete or mortar. Install some small/1" drain lines about every 6'-8' across the bottom that go from inside to outside of the planter on the low side. Then I would seal the inside of the planters with UGL dry-lok,(read the directions and follow them, available at Home Depot) being sure to go down the wall across the footing and over a few inches of the asphalt to create a good envelope with no way for the water to go anywhere but out the drain lines.
Don't bother doing a layer of pea gravel at the bottom as having different soil types only slows drainage. Just make sure your drain line has some durable screening material so it will last and not get plugged up.
Make sure your client knows what you are doing in writing. Have them sign off, memories are short after the job is complete.
Bid the job then add at least 30-40% more because you will need it. Don't feel bad about the bidding thing. When I was starting I used to do a bid then double it and that was the only way I ever made any money.
08-23-2006, 01:58 AM
Thanks for the information. I kind of figured it wouldn't be that easy. That seems to be the "theme" I have been running into in this line of work.........everything takes way more time then you could imagine and always allow for plently of "fudge factor" in the bid. Speaking of, I have found that bidding is my least favorite part of this. I think I might take a pass on this job. *trucewhiteflag* I do 99.9% smaller residential jobs and this is a commercial job........Restaurant. Thought it would be a great way to get my name out there. But it could also backfire if I try to do something out of my league. Seems like alot of stress I don't need...especially since school is starting up, and half of my workforce is gone. Thanks again for the information
08-23-2006, 05:20 AM
So if I do decide to take the job and cut the asphalt, i can use a regular brick saw to cut through the asphalt?
08-23-2006, 06:29 PM
You could, lots of guys favor aluminum oxide blades for asphalt. I would also line the planter with fabric so you don't have soil leaking out onto the paved surface also prevents drains becoming clogged.
08-24-2006, 01:13 AM
Good Idea on the fabric, thanks. I guess I'll get back to this bidding game, send it to them, and see what happens. Hopefully I bid high enough, nothing is worse then when a customer says, "Wow, you are pretty cheap compared to the other guy.":hammerhead:
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