More about greenhouse bases

Hi guys can someone help me? sorry if I'm doing this wrong but I'm a newbie.

I've just taken delivery of a huge meccano set that's reputed to be a 8 x 12 greenhouse, brand new, with integral base. When me and the man can psyche ourselves up, we'll try to erect it. I've read all the stuff in the threads about how important it is to get your base level and your greenhouse square.

Problem is, the 10 x 14 concrete slab where it's going to go isn't level. It looks ok but when you put a straight edge across it you can see hills and valleys in it up to 15mm. I don't want to wreck my new greenhouse by building it wonky.

What's the best way to proceed? :cnfs:
Make a sausage of concrete round the perimeter of the greenhouse and try to flatten it out? Might be hard. Cover the entire slab with another layer of concrete? I'm told it would crack off in time. Cover it with paving flags? Might cost a lot, and having spent a fortune on the greenhouse I'm now broke.
Hope one of you experienced gardeners can help !!

 

15 mm isn't too bad. If it was me I'd put in a single course of bricks on the base and ensure they were level and then lay the base of the gh on that.

 

Sounds like an ideal situation for installing wing insulation

 

Just skim it level use some unibond in your mix wire brush the surface clean that you are going to bond to,if you start lifting it on bricks you will end up with doorway problems.

 

You say you`ve put a straight edge on it. More importantly, have you put a spirit level on it?:thumb:

 

If it was me I think I would not bother with the actual base, assuming its one of those bolt together galvanized or ali jobs, and go with Dave W' s suggestion of laying a course of bricks.

I cant think of another way of actually ensuring that its level and square.

Packing up off the existing base is possible but could be a bit tedious if your not used to that kind of thing, and its supprising sometimes how far things are out of level,(as David says), once you get started.

 

An integral base is part of the frame, Pete, you cannot discard it.:thumb:

 

We need to ascertain the base is level first. The ridges are nothing, but if the level is out by too much, this can cause problems.

 

Yeah I guess it is:D, but my greenhouse knowledge is a bit old fashioned, I was thinking of those ones where you used to buy the base separate, or build your own.

Cant think why the base comes with it, if its a separate part of the frame, surely if you build your own base you dont need it.

 

You will need a bit of a slope to get the gutters to run in the direction you want. (If you haven;t thought about it as yet, then sloping to the back will allow you to have one water butt collecting from both gutters, but you can't do that at the front ... because the door is in the way!! but you can have a butt on each side, of course.

8 x 12 will give you some useful rain catchment during a summer downpour.

 

Wow! Thanks for all the useful advice!

It's not so much ridges as a long slow curve towards one corner and a valley in the middle of one long side, which I think will cause the whole frame to warp once the weight of the glass is in. At present I'm thinking I'll lay a rectangle of long narrow slabs and make sure it is absolutely straight and level. Not sure what "doorway problems" this might cause, though - can you be more specific please Walnut?

 

The important thing is that the base is level. It doesn`t have to be perfect, but should be out by no more than 10mm.:thumb:

 

Ucg in reference to the doorway, the higher you lift the base the bigger the step into and out of your greenhouse,not a problem if you don't mind the step but if if you want access with a wheeelbarrow or trolley it is.

 

Id mark out the dimensions of the base on the slab then lay a thin damp ish bed of 1-4 sand cement mix, level the base with a spirit level and straight edge and allow to dry, bolt down then assemble the rest of the frame.