Thursday, August 05, 2010

How I built the raised beds

How I built the raised beds (and clad them in sandstone)

Right from the planning stage I decided that the railway would be constructed on raised beds between one and two feet from the rest of the garden. My researches had concluded that not only does a raised railway make maintenance and operation easier, it presents the models more prominently. Also, I was preparing for retirement and its attendant decrepitude - one day I will not be able to kneel and stoop quite so easily!

Living in rural Cheshire, I am surrounded by red sandstone. In fact, when landscaping the garden I dug up a considerable mound of discarded sandstone and so I had a ready source of raw material. In addition, a couple of tonnes of discarded rockery stone advertised in the local free paper increased the mound substantially. However, I realised I did not have sufficient stone to construct free-standing walls entirely from sandstone and so an alternative approach was required. Having constructed a lean-to from brick and concrete ('breeze') blocks, I had a surplus which I experimented with, both as a trackbed (see How did I lay the track?) and as walling for the raised beds. The beds for the railway were constructed about four years ago and seem to have stood the tests and ravages of time and so, when my other-half requested some raised beds for her vegetables, I employed the same method (she hasn't realised yet that the vegetable beds are conveniently placed for a possible extension to the railway(!!)).

Building the bed
Firstly I marked out the location for the bed, using a breeze block as a measuring aid:

I then dug the footings for the wall, to the width and depth of the spade. I filled the trench with rubble which I enthusiastically bashed into place with a lump-hammer. This not only broke-up some of the larger chunks, it bedded them down into the trench:
I checked with the boss, who indicated her approval of the progress so far:
I then mixed the concrete for the footings - 4 parts sand, one part gravel and one part cement (see How I mixed the concrete) and shovelled this in on top of the rubble:

The concrete was smoothed down with a trowel and left to set for a day or two.

I then laid the blocks. A mortar mix of four parts sand and one part cement was trowelled on to the footings and a block laid on:
A fillet of mortar was trowelled on to the end of the next block and that was then laid behind the previous block:
 Each block was tapped into place with a rubber mallet and excess mortar removed with a small trowel.
As I was only laying one course of blocks I did not bother to check each with a spirit level. When laying more than one course I use a spirit level to ensure that each block is level and vertical before laying the next.
 Again, my work was supervised and approved by the boss.
As this bed was rectangular in shape, I decided to top it off with pre-cast coping slabs supplied by the builders' merchant. I have used small pieces of sandstone on the top of other beds, rather than leaving the surface open to the elements and susceptible to frost damage.
 My local builders' merchant did not sell corner pieces so I fashioned my own from a stiff mix of concrete.. Without a mould, the corners were difficult to shape as they kept falling off. However, I will add a fillet to each corner the next time I mix a batch of concrete.
 While I was waiting for my handiwork to set, I set to work splitting some of the sandstone chunks I had accumulated.
As sandstone is a sedimentary rock it is often possible to cleave it with a cold chisel and hammer. I found there is a limit to the width which can be achieved as, unlike slate, the strata are less well defined and some blocks are too crumbly to cleanly split. Also, they seem to split more readily if the sandstone is damp.
With some careful cleaving, I've found it's possible to get two or sometimes three rocks for the price of one:
Before cladding the blocks, I filled up the bed with a mix of manure and soil.
 As my soil is quite heavy and clay-like I also added a barrow load of sand to lighten it up:
The whole lot was mixed and raked, with as many stones removed as possible (which have been put into the rubble bag for the next project).
Cladding the blocks
A mortar mix was made (as above) to which was added some red cement dye and a generous dollop of PVA adhesive - to make it more sticky.

Once mixed, the mortar was splatted on to the blocks with a trowel (and a suitably rubber-gloved hand):
The chunks of sandstone were then pressed into the mortar which was squidged around them and tidied up with an old 1.5 inch paintbrush:
 I find this process quite therapeutic. With knee-pads strapped on and something interesting on Radio 4, I can quite happily spend a couple of hours cladding the walls of a raised bed.
 Once again, I had to gain approval from the boss:
After letting the mortar set for a couple of days, I removed the excess from the sandstone with a wire brush. I find it's best to wait until the cement has set sufficiently hard to hold the sandstone in place but still sufficiently soft to be brushed.

 As can be seen, my efforts are once more under close supervision. I use cheap wire brushes which I get in a pack of four from the local £1.00 shop.

Before ..................
 ..... and after..............
As can be seen, after four years, the sandstone weathers nicely and the moss becomes more established. My earlier efforts were done before I found cement dye - but even so, the effect seems quite acceptable.

In only a couple of places has the cladding fallen off. I figure this was due to mixing too much mortar in one batch on a hot day, which meant it had dried out too much when I came to attach some of the sandstone. To remedy this, I now only mix a small amount of mortar and also wet the concrete blocks by 'painting' on some water with the 1.5" brush before smearing on the mortar, particularly when the weather is warm and sunny (yes the sun does shine here sometimes!).

No doubt, any qualified builder or mason will be horrified by my efforts, but as I'm not building structures on which others' lives depend, I am more than content with the outcome.


Anonymous said...

Lovely to see the photos of each step as you built it.

GE Rik said...

Thanks. I'm not claiming to be an expert but sometimes I think it's useful to see how someone has gone about something before having a go yourself. That was my motivation in putting together the blog.

I'm glad you found this posting useful - thanks for the feedback.