New slab extension

[dougwitt]

I am having a new house built and the concrete subcontractor poured the patio slab 7' x 10'. We requested to have the slab 12' x 15'. My concern is that they are going to chose to extend the patio (on all sides) to make it the size that was origionally requested rather than pouring a whole new slab. If they do the extension without tying into the current patio with rebar am I going to have problems with the extension settling at a different rate than the patio, leaving a 'step'?

[Rich]

I don't think it's of much concern - as long as the subgrade is similar in content and compaction. Although I would still tie the 2 slabs together. Make sure there are control joints going from the corner of the existing slab out to the edges of the new slab as it will want to crack there very quickly.. visualize a wedge into wood. Same type of principle as the concrete cures... expands / contracts.