Re: Hollow Core Floors - - Urgent Advice needed

T

tom99

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Hi All,

Building in Cork, and meeting reps from precast concrete firms at the moment for my first floor. This is going to happen very quick so has anybody any advice / questions as to ask them. Has anybody got any idea how much extra work is involved in the build if i use them or should i stick with the timber joist. Any help appreciated. Do they work out much more expensive that the timber joist. House approx 2500.

Cheers,

Tom99
 
Well as far as my experience goes, like anything else, there's +'s and -'s.
They're really quick to install, my builder had them in before I could get to the site. He told me that the crowd were arriving in the morning, and by the time I got there before lunch, they were done, all chucked on with a crane. You have to be aware of the load bearing wall requirement, if they are all to run in one direction, you need at least 100mm, if not more, to support each end. Mine were laid in different directions, but my engineer said that a lot of the time, a load bearing wall to support where the HCBs meet in the middle of the house is the way it's done, I'm sure they'll explain that a bit better though. The fact that its all done so quickly means that the lads doing the roofing can get straight on with it off a good solid first floor base. you'll also need to install suspended ceilings under the HCB, as they are usually quite high, this is a bit of a job, but mine woked out alright. Involves installing a metal frame and hangers to support your plasterboard ceiling. The top side of the HCB will need a cover too, usually a sand/cement or concrete screed, and this allows underfloor heating as well.
I have to say that I'm quite happy with mine, means that none of the nocturnal sounds from the master bedroom ensuite can escape downstairs either.
You should also ensure that there are enough gaps/holes to pull pipes and cables through, and try to get this done initially, because to hire one of the water cooled core drilling drills for going through the HCB costs an arm and a leg. Hope that helped.
 
Depending upon the span - if you have 2 lengths butted together then you will need to have block on flat to supprt - obviously resulting in more blocks, cost of laying as well as a wider inside wall in places.
 
I have them put in + side they are installed quickly the - side is you are limited in what you can change as you go along, less flexability in changing some details of the build.
 
At similiar stage ourselves. Find out about opes and what kind of lintels will be required.Will you need structural or non-structural screed? Also are you using ufh upstairs? We are, but are unsure as to whether we should insulate under as we did downstairs. We've been told we need a structural screed and because of this laying insulation under ufh will not allow screed to attach to HCB? Any of you with experience of this?
 
We put them in during our build, they worked out about EU10k more expensive than timber flooring, but I believe we were taken advantage of a bit there - i.e. we let the builder use his own preferred, local suppliers, in the interests of speed and a quiet life, but I think it would have worked out a bit cheaper if we'd gone with a very competitive quote from Quinn Prestress (in Cavan/Monaghan) who also provide a superior service in terms of engineering.

Our setup got quite complicated in terms of who'd sign off for the structural capabilities etc., our engineer and the hollowcore providers butted heads over a few things, there were delays, as per usual, things had to be altered, and so on.

After all that, I'm unconvinced of the benefits. Sound still travels between floors via the stairwell, and in some respects you may not want perfect vertical soundproofing anyway (e.g. hear babies crying, teenagers sneaking in/out at 4am, etc. :)). Also there are the other problems mentioned above by earlier posters, such as drilling and so on.

I guess there's improved fireproofing by having concrete floors but I believe you can get high-rated ceiling plasterboards too.

To tell the truth, if I was doing it again, I wouldn't bother with the HC - UNLESS I could get it for half the price and half the hassle, which you may well do, I wish you luck with that.
 
You could consider doubling up your timber joists, place your timber ply 1st floor as per normal, then pour a 75mm concrete base straight ontop. Seen a few houses with this done - seems a good idea.
 
Roundy# said:
You could consider doubling up your timber joists, place your timber ply 1st floor as per normal, then pour a 75mm concrete base straight ontop. Seen a few houses with this done - seems a good idea.
Click to expand...

That's kinda like mine......TJI joists on 300ctrs, insul + 70mm screed, above.

OP - are the walls done already? If so, and they aren't done to take hollowcore, it's all a bit moot, really.........
 
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