extending concrete base

[Pedro Popadopolous]

Hi All,

I am extending a concrete bas on which I am building a conservatory. I need to add an extra 320mm to the depth. Do I need to add anything between the old base (only 3 weeks old) and the new 320mm one?

Cheers

[Rick]

Is the base sufficient strength, and you are lifiting it ? If so it may be worth considering adding 320mm of polystyerine in the middle, and making the dwarf walls a bit taller round the sides.

Rick

[<me9]

Insulation?

[Pedro Popadopolous]

The new base will hold the majority of the conservatories weight as its the front edge that needs to be added. So all the doors, frames and the roof will be held on this bit.......

My concern is really, can I just 'Add' 320mm onto the base, or do I need to bolt the new bit to the old bit or do I dig it all up and start again? I am allso wondering about having to 2 DPM's overlapping as I will need a new dpm on the 320mm add on :-)

Thanks

[Rob Morley]

I suspect you're talking about adding to the breadth of the slab. Other respondents seem to be interpreting "depth" to mean thickness. I'm not an expert, but I suspect you'll need to tie the two slabs together with something - maybe some rebar loops fixed into the existing slab (with resin?).

[Christian McArdle]

If you mean depth, then loads of insulation and some embedded underfloor heating pipes and screed (even if you don't actually connect the underfloor heating up yet). If you actually meant width, I'd probably follow Rob's advice, to avoid the two parts going their separate ways.

Christian.