Weight Issues and Wooden Bottom Thickness Question

Mel's Mix Wet Mix Weight:-

So from what I've gathered reading through the past forum threads, Mel's Mix (Dry mix) is approximately 35 lb per cubic foot (approximately 16kg).

Would anyone happen to have a handy figure for Mel's Mix per cubic foot when wet?

I ask because I'm in the process of trying to figure out if I should construct my own box or have a contractor build it out of something sturdier or to get a commercial off the shelf planter.


Wooden Bottom Thickness:-

In view of the former option, I'm most likely going to select a heavy hardwood (either teak, white oak or chengal). My plan is to build the box as show in the diagram below and have it sit on a wall mounted bench (another reason for me to look into the weight issues). I am planning on making a short (height of 8 inches) version to ease up on the overal load/weight.

Which then brings me to the issue of wood thickness and in particular, how thick should I make the bottom of the box if it is to be raised on its own?

Any and all help is most welcome! =D


Apologies in advance for the horrid handwriting and draftsmanship.

Since your 1' front to back depth is so short, you may want to consider using synthetic materials for your base/bottom.  Hardie cement board (which is what I use) or 12" Trex type trim boards would probably never deteriorate.

Hardware cloth and stretchers as reinforcements? I believe there are a few back threads about this subject. Try the search feature.  

In regards to your question about how much MM weighs when wet, I'd suggest getting some dry MM of a whole cubit foot in dimension and then a gallon/litre, etc container and just add some water until your MM is of a satisfactory "wetness".  Then, measure how much the whole thing weighs or simply add the weight of the water to your original guesstimate of 35lb/ft3

The above might help you get an idea of how rugged your container needs to be for the wet MM but it does not take into account how much the plants will weigh, and they can weigh alot.

Good luck!

Merelydicta, You wrote "have it sit on a wall mounted bench." If the box will be sitting on a bench, you can build a 1' x 4' box out of 8" cedar fencing with a 1/2" plywood bottom if you use screws instead of nails. You may want to add a 1" x 2" cross bar in the middle to keep the front and back from bowing apart. I have several 1' x 3' boxes made of 8" cedar fencing with 1/2" plywood bottoms. They sit on brick patios or 2" rock beds.

The strength of the bench support is what needs to be considered. It may need legs at the front, or angled supports underneath. Was the Bench used as seating for at least 2 people? If so, it probably won't need any reinforcing. Good luck with your project. 

toledobend wrote:Since your 1' front to back depth is so short, you may want to consider using synthetic materials for your base/bottom.  Hardie cement board (which is what I use) or 12" Trex type trim boards would probably never deteriorate.

 Hi toledobend,

Thanks for the suggestion!

I'll definitely look into that...I never considered synthetic materials =D

camprn wrote:Hardware cloth and stretchers as reinforcements? I believe there are a few back threads about this subject. Try the search feature.  

 Hi camprn,

Thanks for the helpful suggestion.

I did try the search feature but I was focused on weight and thickness as key words. It didn't occur to me to search for reinforcements as a key word. =D

mollyhespra wrote:In regards to your question about how much MM weighs when wet, I'd suggest getting some dry MM of a whole cubit foot in dimension and then a gallon/litre, etc container and just add some water until your MM is of a satisfactory "wetness".  Then, measure how much the whole thing weighs or simply add the weight of the water to your original guesstimate of 35lb/ft3

The above might help you get an idea of how rugged your container needs to be for the wet MM but it does not take into account how much the plants will weigh, and they can weigh alot.

Good luck!

Hi mollyhespra,

Thanks! I think for me, the problem I'm having is that I'm trying to do too many things at once. My current place is undergoing renovation and I've gotten my contractor to construct a wall mounted bench out of an old gate. As such, I haven't started going about creating my Mel's Mix yet (that'll only occur once I move in about 1 and a half months). So it's kinda like a chicken and egg thing trying to figure out the weights/load expected.

I've never done SFG before. Container gardening yes...a few paltry attempts so I have no real basis for understanding the issues I'll be facing outside of theory and whatever is in the ANSFG.

But I'll most likely go down your route if all else fails =)

merelydicta wrote:

camprn wrote:Hardware cloth and stretchers as reinforcements? I believe there are a few back threads about this subject. Try the search feature.  

 Hi camprn,

Thanks for the helpful suggestion.

I did try the search feature but I was focused on weight and thickness as key words. It didn't occur to me to search for reinforcements as a key word. =D

Have you seen this thread?
https://squarefoot.forumotion.com/t297-building-a-table-top-sfgsome-ideas?highlight=building+tabletop

sanderson wrote:Merelydicta,  You wrote "have it sit on a wall mounted bench."  If the box will be sitting on a bench, you can build a 1' x 4' box out of 8" cedar fencing with a 1/2" plywood bottom if you use screws instead of nails.  You may want to add a 1" x 2" cross bar in the middle to keep the front and back from bowing apart.  I have several 1' x 3' boxes made of 8" cedar fencing with 1/2" plywood bottoms.  They sit on brick patios or 2" rock beds.

The strength of the bench support is what needs to be considered.  It may need legs at the front, or angled supports underneath.  Was the Bench used as seating for at least 2 people?  If so, it probably won't need any reinforcing.  Good luck with your project. 

 Hi sanderson,

Thanks for the helpful pointers!

Would you be able to post a photo or two of your boxes? I am having trouble visualizing it (e.g. when you say 8" fencing, does this mean the pieces are 8" thick or long?). Additionally, there isn't much call for wooden fencing in Singapore (mostly wired fencing here if at all - it lasts better in the humidity and heat) so I'll most likely still be sticking to wooden planks.

Thanks for the really helpful tip on the 1/2" bottom! I was planning to use 3 x 4' long 4" wide planks to form up the bottom which would've made the thing even heavier than it ought to be.

The bench will have angled supports (triangular struts) to it. As for the weight, it's definitely a question I'll be asking the contractor over the weekend as the issue only occured to me when I started looking into the thickness of the wooden bottom/weight of wet MM.

camprn wrote:

merelydicta wrote:

camprn wrote:Hardware cloth and stretchers as reinforcements? I believe there are a few back threads about this subject. Try the search feature.  

 Hi camprn,

Thanks for the helpful suggestion.

I did try the search feature but I was focused on weight and thickness as key words. It didn't occur to me to search for reinforcements as a key word. =D

Have you seen this thread?
https://squarefoot.forumotion.com/t297-building-a-table-top-sfgsome-ideas?highlight=building+tabletop

Hi camprn,

No I hadn't. And now that I have, it's answered some of the questions I had!

Boffer's TT garden looks amazing!

Thanks for surfacing this to my attention =D:thanky:

I thought of Gwennifer and the 3 strong table tops that her husband built for plastic trays, but I didn't bookmark it. I only copied the photos to a word doc, with the different heights measurements and the name Watermelon Smoothie!

Merelydicta,  I took some update photos today.  Here is one of the 1' x 3' boxes my husband built using cedar fencing, 1" thick, 8" wide, 6' long boards.  The black fabric is weed screening that will be on the bottom of the box so that the Mel's Mix doesn't wash out the holes drilled in the bottom.  There are 1" holes in the 4 corners and one in the center of each square.


Here are 2 boxes, each 1' x 3' with plywood bottoms.  They are set on rocks with weed fabric on the plywood bottoms.

A 4th box 1' x 3' with plywood bottom.  Sitting on pavers.

sanderson wrote:Merelydicta,  I took some update photos today.  Here is one of the 1' x 3' boxes my husband built using cedar fencing, 1" thick, 8" wide, 6' long boards.  The black fabric is weed screening that will be on the bottom of the box so that the Mel's Mix doesn't wash out the holes drilled in the bottom.  There are 1" holes in the 4 corners and one in the center of each square.


Here are 2 boxes, each 1' x 3' with plywood bottoms.  They are set on rocks with weed fabric on the plywood bottoms.

A 4th box 1' x 3' with plywood bottom.  Sitting on pavers.

Hi sanderson,

Thanks so much!

The photos really help! I wasn't familiar at all with the term "fencing" and I visualized little fences forming the sidewalls  

I was actually considering on halfing the thickness of the sidewalls to 1/2 inch thickness as I was concerned about the overall weight of the box. I would be using dividers to both function as the grid and to lend additional structural strength to prevent the side walls from bowing out.

I will also most likely go down your route too and use a teak/plywood bottom of 3/4 - 1 inch thickness.

I've found two timberyards that carry teak wood and once the renovations are completed, I'll head down to work out the order. I plan to leave it unfinished to (a) avoid chemical leeching issues (b) let the teak weather out nicely over time.

I'll be using larger planks so I intend my final order to be as follows:

2 pieces of 10" x 4' x 1" thick boards;
2 pieces of 10" x 1' x 1" thick boards; and,
1 piece of 1' 2" x 4' 2" x 1" thick board

Hopefully all goes well =) and will post the photos up to help others as you have with me =D


Thanks once again! The photos are a great help!

Merelydicta, How is your project going? We haven't heard from you for a while?  

sanderson wrote:Merelydicta,  How is your project going?  We haven't heard from you for a while?  

Hi Sanderson,

Thanks for checking in on me. I've been kept busy at work.

However, I am glad to report that some level of progress has been made. Hope the photos help show what I intend to do  

Here is my kitchen garden. I decided to get fully grown plants from the nursey whilst I try to suss out reliable vermiculite dealers here in Singapore (proving harder than I inititally thought). I've got a mix of Rosemary, Curry Leaf plant (Murraya koenigii aka Curry Tree), Laksa Leaf plant (Persicaria odorata aka Vietnamese Corinander), Oregano, Thai Basil, and Sweet Basil. This area gets full sun all day so I'm more or less deep watering them in the mornings before I leave for work and at nights before I head off to slumberland.




Here is the SFG planter box with trellis (It's approximately a single 4 square foot row). Once I can get my hands on a reliable supplier of vermiculite, I'll be actively using this area. This gets full sun during the early and late afternoon.




Here is the in-built planter box on the balcony with a fresh bed of pebbles I laid down. I'm not sure if it is clear from the photo but the green sticks are going to be in that slanted orientation as I fill it in with MM. There'll be a mesh netting linking a line of sticks all down the length of the planter as I intend to do a 45 degree trellis to allow the plants (probably squash) to creep outward to get more sunlight under the brise-soleil that extends beyond the balcony.

Forgot to add that the kitchen garden area is approximately slightly under 2 feet wide and 6 feet long so there's still some room to expand.

So I managed to get some free time in and these are the results.

I decided to go with ANSFG's recommendation of using 100% compost in lieu of MM. I will report on how it holds up in tropical conditions.

I've re-potted some of the plants in the kitchen growth area into better planter trays that have in-built reservoirs at the bottom. I noticed that on particularly hot days, the plants were wilting in the heat. Based on my measurements, each steel basket will hold 3 trays comfortably (each tray holding two herbs with room to spare).



Here's the balcony planter area with a layer of compost laid on top of the gravel bed I put down. I've also put up the 45 degree trellis to allow for the squash and other creeping planters to extend past the brise-soleil. I'll be putting down about 3 more layers of compost before I begin planting the seeds.

Merelydicta,  I notice that you don't have any mulch on top of the MM.  It's a life saver during the heat, especially for plastic pots.  I use pine/fir wood chips.  Others have their own preferences.


PS Your garden is so pretty.

sanderson wrote:Merelydicta,  I notice that you don't have any mulch on top of the MM.  It's a life saver during the heat, especially for plastic pots.  I use pine/fir wood chips.  Others have their own preferences.


PS  Your garden is so pretty.

Dear Sanderson,

Thanks for the compliment.

The weather has taken a turn for the worse and it's rain and more rain as we head into another monsoon season so for now mulching isn't a primary concern - ensuring adequate drainage is!

But I definitely will keep the idea of mulching at the forefront when the next heatwave hits.

Thanks!