Suspended floor or concrete?

theGrinch

Building out an extension and we need to go down another 40cm to hang joists. This is about 7.5 cubic metres of additional material to be removed.

Builder has suggested we pour 150-200mm of cement and have 100-150mm insulation.

Just interested to know the pros and cons of this and of concrete floors - its for a kitchen extension.

Owain_Moneysaver

Concrete floors are much better if you are going to have a washing machine in the room - they don't bounce, or rot if there's a leak.

Seriously consider having a concrete floor laid to a very slight fall with a floor drain built in. Then you can just hose the room down :-)

MX5huggy

A solid floor is better IMO. You can lay any floor covering on it without difficulty is tiles won't crack. Consider underfloor heating with it, rads are difficult to position in a lot of kitchens. I mean wet underfloor run off your boiler not electric mats.

Insulation wise words 100mm of kingspan/Celotex is probably ok but you want 150mm of polystyrene if that is what is proposed if you go for underfloor put the insulation between the screed with the pipes and the concrete slab.

lush_walrus

I would always go for a solid floor. Downside is needing to leave time for the concrete to go off, timber you just carry on. Generally 28 days are allowed for concrete to go off. It's more expensive to run services through in the future. Timber is dry so doesn't have that issue of time to go off and it's easy to run cables etc through

Long run though and concrete will have less issues and is a more stable material.

theGrinch

Thanks for the answers.

Having initially extended 3 years back, we are adding a room onto the kitchen (left untouched) - the additional room itself will become a dining area with one radiator.

Thinking of finishing with laminate.

Can I use the same c30 as for the footings?

jk0

You can get ducts to set into concrete floors so that heating pipes are easily serviced.

Marktheshark

Solid floor, pipes round wall old style and it saves a lot of money and maintenance.
Once laid it can be walked and worked on in 48 hours and cures in 14-21 days to 95 RDH if in an enclosed room and they use a good approved top screed.

Heedtheadvice

Personally, I would opt for ' concrete ' and insulation/screed but on beam and blocks. You can thus have something very easy/quick to build and have a void below for services and future access / maintenance (provided you don't need to go through same floor!!!)

theGrinch

The builders have offered to mix the cement for the floor (and in fact the footings by hand/machine). The logic being they will have more time to get the floor and its various layers right rather than a readymix truck pressing them.

Should I be wary or is an experienced team well able to get the mix right or near enough right for floor and footings?

Silver-Surfer_2

theGrinch wrote: »

The builders have offered to mix the cement for the floor (and in fact the footings by hand/machine). The logic being they will have more time to get the floor and its various layers right rather than a readymix truck pressing them.

Should I be wary or is an experienced team well able to get the mix right or near enough right for floor and footings?

I would think an experienced team could get the levels right from a ready mix truck.

Marktheshark

They dont get "time to get levels right" it has to be poured or pumped and laid in one continuous shift or will crack and expand.
The fact they dont know this basic means you need a floor screeding firm in to do the work.