Newbie needs help on base for metal shed please !

[Aneng]

Hi !

I'm planning to put a 6' x 7' metal shed on the garden lawn and would be very grateful for some advice on base design please.

I live in a rented house, so I cannot really go pouring concrete or making anything I can't remove when we leave. It's been suggested to me that I make a raised bed of tanalised shuttering, hardcore, sharp sand and flagstones on the lawn. I knocked up a plan using Google Sketchup (free CAD package, great fun !), and came up with this.....

Can anyone make suggestions to improve this please ? e.g. should I really be making the flagstones exactly the same size as the shed to avoid rain running off the roof and onto the 'margin', (and therefore inside the raised bed) ? Should I be putting a plastic damp proof sheet in there, and if so, at what level vertically and how wide / long ?

Another problem is that the lawn in my intended location is always damp and the ground is quite spongy (big hills behind us) - will this raised bed design be ok here ?

The alternative is to put it next to my greenhouse here...

but the ground there is a broken mess of very badly made concrete that's crumbling and can be lifted by hand, plus it's also on a slope toward the greenhouse and I'm concerned that it would block out too much light for the plants in there. I suppose if I did put it there, I could make a solid concrete base, but the thought of having to prepare the ground and build up a breeze block frame etc, puts me off - that sounds too complicated for me.

Any ideas ? / suggestions

Many thanks.

 

[chessspy]

Hi, aneng,
your idea looks ok, especially if you will have to uproot it later.
If you are worried about damp coming up through the floor, you can put a DPM (damp proof membrane) under the final layer of sharp sand under the slabs.
I would bed the slabs on drylean, which is sand cement mixed dry and tamped which you then lay the slabs on, it will set but will break up fairly easily later if necessary.
If you go for the raised option, you can use the top edge of the wood as a screeding edge, by cutting a plank with 2" bits out of the ends ,so that your slabs finish level with the top which looks better.
Don't dot and dab lay them, screed all ofer flat and smooth and just lay them on, 1/2" gaps between and point in with an iron to secure them with some of the drylean, don't just brush it in.
Use a string line to keep them straight and level.
Put a bit of a fall on overall, 2" should be enough.
if you measure the slabs first, you can make the size of the frame to suit no cutting.

 

[Aneng]

So, should I have the flagstones flush with the shed walls (i.e. no 'margin'), or slightly larger than the shed ?

....and should I have the shuttering underneath the flagstone edges or outside ?

i.e. Which one of these ?

A)

B)

C)

D)

E)

or.....

F)

Sorry for all the images - I just love playing with the cad package

 

[big-all]

the trouble is unless you have a raised floor in the shed it will "leak" as water runs down the wall and gets directed under the walls

idealy you need the sides to overhang the base to stop water being driven under

dependant on construction you may need the base going to the outer edge to fully support the shed

now the trouble with metal and plastic sheds/storage huts is the amount of condensation you get during the cold damp winter months

so dont plan to leave anything in the shed that you wouldnt happily leave outside in the rain

ventilation will help remove the moisture but any driven under the sides when raining wont help

 

[chessspy]

Hi, D or E look good to me.
I've never tried a raised bed before, but with a slight fall there shouldn t be much problem with damp.
however if you are worried, you could raise the base of the shed on tanalised 2x4s spaced as floor joists, running with the fall.

 

[Aneng]

Ooh... the reason I was getting a metal shed was because I thought they were drier than wooden sheds. Is that not the case then ?

 

[Bodgeit and scarper ltd]

Metal sheds are a waste of money; it will be wetter on the inside than on the outside. Get a wood shed and you wont get any damp. A wood floor is best, or no floor is better than concrete.

 

[big-all]

wood breathes and absorbs moisture

my workshop [12x10ft] is constantly around 3 degrees and only at 10 degrees [takes around 30 mins to warm up]during the winter days i am working as the glue wont set at below 8 degrees i use a 2.5kw fan heater with a frost stat[3 degrees]

i often have several days when the shed will be near to freezing without damp

the shed remains tightly closed without ventilation during winter months

i probably get 1 or 2 percent rust on unused metal tools
all metal will be cold but not damp

 

[chessspy]

Hi, My 'shed' is 4" conkers, (reclaimed brick front) clad inside with reclaimed 4x2 and plaster board (insulated to 100mm)
warm in winter, cool(ish) in summer.
Costs cuff all to heat. useable all year round.
See it on google earth 3, ME2 3AB.