Question
QUESTION: I am going to build a couple of beds on both sides of my deck and against my brick house.  Therefore, I will be using field stone stacked about 18 inches high for the front border with the deck and house providing the border on the side and rear. I have 2 questions.

1. Do I need to remove the bermuda grass if I will be backfilling with 18 inches of topsoil.

2. Are there any drainage issues that I should consider for elevated beds of this nature?  Each bed will be about 5X8

ANSWER: Yes & Yes

You will curse the day you decided to plop a planter on top of bermuda grass without first either killing it chemically, or physically ripping it out.  I've seen lots of methods to try and save a step, by building on top of it, but it has the tenacity of those horror-movie creatures that just keep coming after you!!  Don't take the risk - kill it now, or fight it coming up into your planter bed for the next ten years.

Drainage - as you are using field-stone stacked walls, if they are like an elevated planter with 4 sides, it isn't as much of a concern as water will weep out of the stack-stone cracks (assuming you do not mortar them).

BUT if you are using the side of your house or wood decking as one wall of the planter, then YES - protect these with a barrier and drainage device to ensure water is transmitted away from them - moisture is not a good thing for houses, crawl-spaces, or decks.  

Either a barrier or perforated drain pipe should do the trick (ndspro.com, or similar drainage product supplier can be a good resourse for this).

~M






---------- FOLLOW-UP ----------

QUESTION: Thanks for the prompt reply.  What about weed fabric?  Is that necessary to line the inside and bottom after I remove the bermuda?  Also, would thick black plastic provide an adequate barrier on the deck(which is pressure treated wood) and brick?

Answer
Weed fabric: Lining the bottom won't help much.  We specify it all the time here (under rock mulch), but it only buys you about 5 years of weed-free bedding.  Seeds blow in from all over the place & pop up all by themselves on the top side. Nasty rhizome roots like Bermuda's are programmed to burrow through just about anything you can put it their way. Weed fabric and the heavy black plastic will break down over time & UV exposure, so their effectiveness is not for ever.

That said, anything is better than nothing.  It also depends on which way you slope the beds - Away from any structure is a MUST.  Don't make a pond against the deck with the moisture barrier/liner, as the goal is to direct the water away from being trapped against anything that might get damaged by long-term moisture exposure.  Water is the enemy of home maintenance!!

The black plastic should not be used under any mulch at the plant base, as plants "breath" through the soil.  Weed barriers are permeable/black plastic is not.

Here, were we get 6 inches of rain a year it isn't as important as Florida or Texas and their 60+ rainy seasons.  Here is the professional-grade moisture barrier we specify:
http://www.ndspro.com/cms/files/WaterBarrier_1.pdf

Good luck!  ~M