Sagging/Unlevel shed base

[sinkorswim]

Hi

Problem is that my new 4.5m x 3.5m concrete summerhouse base appears to be pooling water in a couple of area (largest is about 1.5 m square and the other is more of a 2m x 30cm strip). I assume that it has either sagged whilst drying or was not levelled, possibly the wood used for tampering may have been bowed. The base was only put down in middle of last week and nothing has been put on it yet. Can anything be done to level the concrete? Such as skimming and re-levelling? Or best to cut drainage channels or drill holes? Any suggestions? I'm concerned about the summerhouse will stand in water and it won't be good for the structure as the base is not completely flat.

Details: I have been working on landscaping my garden, removing a huge area of concrete/brick structures to be replaced by two new bases - large one for a summerhouse and also a small greenhouse, and gain back some garden. I recycled smaller pieces of broken brick/concrete for sub-bases, and the big bits went on the skip. Sub-base was at least 6" deep, which has been down since start of the year before/during all the heavy rain. I did the shuttering myself using 1" gravel boards with a slight slope to the back of both bases just before concreting. A local builder wacked down my sub-base and concreted both bases on site. Went for 6" reinforced concrete for the summerhouse because of near by trees. I was expecting to get a 4:1 mix, but then they said something about 5:1 at the time, and was told afterwards that it was "1 in 6". They used all-in-ballast.

Thanks in advance

 

[ntb]

You could try putting a 4.5m x 3.5m summerhouse on top of it to keep the rain off...

 

[sinkorswim]

That would have been a massive summerhouse! However, the one that I have already purchased (and am painting in the garage in preparation) is 12'x10' which is sufficient for me.

The base is larger than the intended summerhouse for a number of reasons; I need to bolt down sleepers onto both the two sides to retain banks of earth that have mature plants (I dug out an unused bank of earth behind the old concrete/brick structure, and the bolts have been set in the concrete). Also wanted to use the base for garden storage, log storage, a water-butt, etc.

 

[ntb]

Ok, then sit the summerhouse on some slabs on top of the base to keep it out of the water.

 

[sinkorswim]

Wouldn't the slabs rock on the concrete and the fact that it is not level be bad for summerhouse structure? I could have easily laid slabs myself but I wanted to get a proper base installed for longevity and to avoid problems with doors and windows, etc.

 

[ntb]

Not if you bed them on some mortar and make them level. There is a certain amount of flex and give in timber anyway and no wooden structure is going to be built with millimetre precision.

The other option is to cut a channel in the base around the footprint of the summerhouse with a drain channel leading off of it to stop any water getting under.

 

[r896neo]

Tell you idiot you paid to do it to sort it out. Its pretty fundamental stuff

Seeing as its reinforced tearing it up will be a nightmare.

Laying paving as ntb said may be your best bet.