Hi All,
Ive just bought a 6x8 greenhouse and due to the garden sloping so bad, I went ahead with level concrete base.
First to do it get planks of wood to the size of the base wanted. Make sure at least 12 thick and at least 5" wide. We had used scaffold boards, check ebay. They where £2.50 for 6" and had to join.
The second hard part is digging out a hole to the size of plot wanted and getting level and square. Make sure you have at least 3" on concrete.
I would also suggest at least 1.5 foot around the edges for access, you will want to clean the windows every year.
Once level and square. Make sure everything looks like and make sure base does not go lower than the highest point as you don't want water to run over your base.
At this build stage you can add drainage like ive done, was about £40 with ends and attachment for 100mm pipe. Great as makes sure water goes outside and not left on floor, plus easy to clean floors.
Next do you want electric in your greenhouse, I thought why not. Add lights, heaters etc. More expensive to do, I went for blue water pipe from wickes, 20mm one about £17. 25m 1.5mm Rubber wire from screwfix £25 and drilling a hole to the back of your wall, you can add this to ring main at the back of socket, but I would always ask a qualified electrician to put electrics in, but do the hard work and you can save money. Trick, get some silicon spray and spray cable, this will make your cable so much easier to enter into the 20mm blue pipe.
Once you have done everything above, ready to buy concrete bags, and ballast. For our base we used 1.5 tones plus hardcore, but was very deep at the back and 5 bags of watertight bags of 25kg wickes concrete. Always get more than you need, you can return bags you don't use. Under estimate and you will find wasted time going back half way though. Yes we did. I would also recommend single bags of ballast, if buying 10 a time works out cheaper and if buying a lot like 1.5 tones, works out only £10 more on a jumbo bag, but easier to add to mixer and less work. Mind the car, 10 bags is a lot for most cars to carry. Do it in multiple trips, plus breaking the car will take longer, so take care. Maybe worth checking max weight.
We had a cement mixer we could borrow, but I think for £35-40 you can rent for a weekend.
Two people working is always best.
Set a side at least 4 hour on a good day to do concrete. Check weather report, you need a day for the base to set properly and cover if raining or if frost is forecast then cover also.
Tapping the base once some concrete is added, with wood will get more water out and this makes a nice smooth surface.
The finished result today.