I am currently quoting on a floating seat, like in the picture below:
Although our seat does not have the right end wall like the picture!! Brilliant.
Here is the drawing:
The orange area is decking, which will be +570mm above the grass area. The current ground level where the decking will be is the same as the grass area.
So the overall height of the planter from current ground height will be approx 1400mm, with a seat height of 1020mm from current ground.
S the planter will be quite considerable in height from the grass area/current ground height and the planter is 440mm wide.
There will only be 400mm approx of masonry above the seat height, and it will be constructed of a 100mm block front and back leaving a 140mm gap in the centre for planting.
Question obviously is support for the seat!
This is what I am thinking:
Built from block, 2 parallel courses of block layed flat as the planter is 440mm wide. This will be built up to the height of the seat. So it will really be one solid structure up to that point.
My problem is, there isn't enough masonry above the seat for me to cantilever steel plates or angle irons for the seat support.
I am proposing to have a series of steel supports made up like so:
Each support is a 250x250mm, 6mm flat plate with a 70mm x 8mm flat bar say 1200mm,(I can cut down on site) welded from the centre of the plate coming vertical.
I will build the plates under the first course of blockwork, so all the vertical flat bars come up through the centre joint in the blockwork.
At the point where the seat needs constructing, some 4x3 angle irons with an end plate welded to one end to be built in to each perp of the block, (so every 440mm) and bolted to the vertical flat plate.
Kind of like this:
There will be a timber skirt of the seat to hide the ends of the steel work.
weve done these before using 40mm s/steel bars built into the planter from one side to the other at 300 centres which were left out of the wall 300 then we drilled out the teak slabs 500mm/4000mm and slid them on using a d3 expanding glue job done
Cant use 40mm bar as the wooden seat planks the customer has are 22mm.
I could use the angle iron from one side of the planter to the other but I would still be concerned about there not being enough mass on top of them to keep them from moving.
If my original idea seems over engineered, my other plan is to put the angle irons straight through leaving them out of the wall as per my other spec, and also epoxy resin 2, 6mm threaded bar per angle iron down 400mm or so into the blockwork and through the angle iron, locked of with an m6 nut and washer.
We've also done this using bars through the planter. We used Scaffold tube going through the front wall to the back. Build it in as you go. 400mm of block and topsoil is plenty of weight to stop it going anywhere. If you stop the bars short of the face of the bench or build a facing plate out of the same timber ( like in your pic) you won't see the supports.
240mm wide is a bit skimpy for the planted space. Id put at least 100mm on top of that.
We used sleepers so just rested them on and fixed with a u shaped pipe fixing. If you're using decking boards or similar you'll have to make up a frame work and attach in the same way. Then fix your deck boards to this.
