Laying laminate: How do I handle uneven concrete subflooring

[zorba]

The concrete subflooring is only uneven in one spot, where two previously separate concrete floors meet (two rooms, kitchen and diner, were knocked into one). The drop is say 8mm at maximum. The subfloor drops down from the diner to the kitchen, and then as it progresses into the kitchen area the subfloor rises back up, to the same level as the diner, over a distance of about 0.5m (and the same wide).

There was a higher edge in the diner, a "lip" or a "crest"...just the last cm or so was 1mm or more higher than the rest of the diner. I've taken a bolster chisel and tried to scrape this down with some success. However, the diner floor is still higher than the lowest part of the kitchen floor some 15cm away.

What's the best way to deal with this?

I had initially thought about mixing some concrete (never done this before!!) but I'm at sea as to the recipe to use... also the quantities I need might not justify the effort and cost (what's the smallest bag of cement and sand one can buy?!?). Then I read somewhere in a forum just now about self-leveling compound?

I would estimate the area of fill to be 0.5m2 (half a metre squared) to a max depth of 8mm, but leveling off to zero (ie. not a "box" shaped fill, more like a puddle shaped fill... lol).

I want to get this done tomorrow so my buddy can lay the floor on Saturday, so time is *ideally* of the essence.

** edited: max depth changed from 5mm to 8mm (I resurveyed) **

 

[Doggit]

You need a self levelling compound to fill the wholes, but depending on ho good you are, you may need to do the whole floor.

Look for this sort of thing. http://www.tilegiant.co.uk/professional-self-levelling-compound-slc-1550.html?, but most SLC will do the job, just make sure it has a fast setting time if you want to work on it on Saturday.

 

[zorba]

Thanks Doggit! Do I just add water?

I went back and checked the max. depth again... its more like 8mm, but the area is smaller than I initially estimated. approx 0.5m x 0.5m... Will this compound still be okay with the new depth?

Also since total volume is only going to be (max) 50x50x0.8 cm3 i.e. 2000cm3 or 2 litres, I should be able to get away with a smaller bag, no?

Does this stuff even off nicely to zero?

Thanks again mate, appreciate the answer!

 

[Doggit]

The rule of thumb in this sort of problem, is that if the job can go wrong it will, so don't try and be too stingy with your materials. You'll have no problems with the depth, but they don't often level off to zero very well - but I wouldn't worry about that too much, as the laminate underlay should handle little bumps.

 

[dazlight]

For that area you want a bag of Ardex rapid repair mortar . A45