Unlevel concrete

[smudge]

I have just had a double garage built in the United Kingdom and the builder has layed the floor concrete very unlevel and uneven. It sags nearly 3 inches down in the centre of the garage compared to the edges.

I want to rectify this and make it reasonably flat myself and would like to ask if anyone knows the best way to do it?

On the edges it is almost at the height level of the damp proof course in the brickwall. I do not know if laying a new screed can either go above the damp proof course or alternatively whether a new concrete floor screed can go down to be almost no thickness as the floor gets near the walls?

I dont think I can use a self levelling compound as the depth of the sag in the centre of the floor is too much. I am at a bit of a loss to know the best remedy. Coud it be best to just lay more runny concrete over the the top of the existing floor? Or mix up a special ratio or type of concrete an dlay it with a plastering trowel.

Ild would realy like to do this myself as the builder I have lost confidence in and dont want to offend him. And also he still hasnt finished the roof which Ive been waiting weeks while he is started another job at the same time as mine so I would wait for ever for him to rectify it !!

any sugestions how I coud fix my floor an dmake flat woul be realy appreciated. Thanks in advance

[Rich]

Many times a slope is integrated into the slope for drainage reasons. Although I think 3" is too much but I would talk to the builder and see what his reasons are first. If he says it's the way it should be and you think it's too much.. well I guess it should have been discussed prior to placement. My suggestion was going to be a plasticized concrete - pea gravel mix.. kind of like a self leveling pour but able to pour deeper sections.

[grumpydasmurf]

3" in the cetner? Unless there is a drain expect a puddle. I'm not a concrete expert but I had a similiar problem with my own home )condo building). We decided to take concrete and mix an epoxy bonding agent with it. We then applied a 1" thick layer of concrete at the highest point and applied enough concrete on the remaining balcony to level it so there were no sags and proper pitch.

Like CR said consult your builder first.

[smudge]

Thanks for advice, I liked the idea of the type of morter you sugested. BTW there wasnt any reason for the builder leaving a big unlevel floor he was just careless. Should have done myself I guess and will do it myself as so Iam sure it is right this time!
I have decided the best way is to take your advice on the floor matrial and build up a screed on to the top of concrete. Because it will need to be a minimum of 40mm and so will go above the Damp Proof Course I think I will be best to coat the edges between the existing floor and wall up to where the top of the screed with a liquid damproof so that I do not get problems with damp