Put cardboard down first :)

Works great to kill the weeds, and the worms love it.

By year two, it'll be disintegrated into the soil with no problems :)

Is that the only viable way to do it? I was really hoping for something easy like a spray. Its not going to be easy to find 540sqft+ of cardboard before this weekend with everything else I have to finish before then.

sounds like you want to use spray. I wouldn't but................

Supposedly Round-up is inert after it touches soil, like I believe ANYTHING MONSANTO says, but even that would take a while to kill vegetation. If you are really intent on building your beds soon, you could use a weed cloth, but your plants couldn't penetrate it either. I have weed cloth under my beds but mine are 16 inches deep.

Cardboard is a great alternative, and you can get it from appliance stores. Just ask for it from their recycling. Just try not to get the glossy stuff, printed is ok though.

Those are my suggestions, but without further information, I can't suggest more than this. Good luck and let us know how it turns out!

Here is a link that might be useful: Sinfonian's garden adventure

The best advice has already been provided. Add a layer of cardboard to the bottom of your beds and add your soil on top. By the time the cardboard breaks down, your weeds and grass will be dead.

Anything you spray contains chemicals and takes time to actually kill the weeds.

Rachel
GrafixMuse's Garden Spot Blog

The beds are made out of 2"X8" material. I'm a little reticent to use cardboard. I live in an extreme environment. Two years ago we had 110+ degrees every day for over 100 days in a row. Its common for us to have 5+ months of temps over 100 degrees. I was told I should dig into the native soil to break it up and mix it with the soil I will be adding. The whole idea is to let the roots go deeper than the raised beads and into the ground. I don't see how this will work if I put a barrier of any kind between the soil in the beds and the native soil. I was hoping there was something I could spray on the small amount of weeds and grass that is sprouting inside the beds that are ready to be filled.

I don't know if this makes any difference. I plan on putting a weed barrier on top of the soil I add to the raised beds.

You're going to need to mulch really heavily in our heat. I've found that I never get a weed in heavy mulch. If I get a weed, it's time for more mulch! Leaves, pine needles, yard chips, paper shredded, even wood shavings, hay from the feed store.
Those cedar chips from HD look really nice.
Mulching will keep the soil cool, save on water and prevent weeds. No need to spray nasty round-up. In your walkways, you can lay old carpet and mulch heavily as well.
Have you ever visited "the Farm" at South Mountain"?. Their walkways are mulched with eucalyptus chips and smell heavenly!

Round-up really only works when the Bermuda is actively growing, which it isn't right now. I can't think of anything else that would be remotely safe to put on a garden. 2,4d won't touch bermuda and will be bad for the garden, I think. Of course, diesel and oil kill Bermuda but who wants that in their garden?
One or two layers of cardboard on bottom and lots of mulch on top really will work. No worries!
Leave the spray for your trees if you must.

There may be a forum for growing in extreme heat, but I'm not one to help you. We have mild temperatures and it's never got above 100 here in my 38 years.

If you want you can rip up the sod and turn it over then build over it. The grass will compost in place over time.