Ground floor ceiling

Cavanjack

I'm a bit away from it yet but was thinking about how to do the ceiling on my ground floor. I'm putting in concrete slabs on the first floor and leaving a 200mm cavity below the slab for mhrv ducting. My question is should I use insulated slabs for the ceiling or just normal plasterboard.
Without the insulated slabs it means I will have to heat the extra 200mm void.
Thanks for any replies.

BryanF

Cavanjack wrote: »

I'm a bit away from it yet but was thinking about how to do the ceiling on my ground floor. I'm putting in concrete slabs on the first floor and leaving a 200mm cavity below the slab for mhrv ducting. My question is should I use insulated slabs for the ceiling or just normal plasterboard.
Without the insulated slabs it means I will have to heat the extra 200mm void.
Thanks for any replies.

It's within the external heated envelope so no need for insulated slabs, remember to adequate access points for future maintenance of hrv ducts

heavydawson

BryanF wrote: »

It's within the external heated envelope so no need for insulated slabs, remember to adequate access points for future maintenance of hrv ducts

Hey CJ,
Are you planning on putting UFH upstairs? If so, ensure you've got insulation under it, so you're not heating the slabs below it. Minor point, but thought it was worth mentioning it.

mfceiling

Just a quick point that if you plan to use insulated slabs then the hanger distance on the suspended ceiling must be reduced due to the additional weight.

Extra main runners would need to be installed also.

I've only ever done 2 ceilings where insulated slabs were screwed up - at this stage i've done over 100 domestic houses and countless apartments.

What i have seen before on a house in offaly was kingspan board fixed directly to the underside of the hollowcore and then i put the suspended ceiling below this.

Would it not make more sense not to leave out the insulated slab and let the heat go into the hollowcore and use it as a thermal mass or if you really want to insulate it then roll rockwool above the metal channels?

Cavanjack

heavydawson wrote: »

Hey CJ,
Are you planning on putting UFH upstairs? If so, ensure you've got insulation under it, so you're not heating the slabs below it. Minor point, but thought it was worth mentioning it.

Thanks for reply. Yeah putting UFH up stairs and planning on 50mm insulation underneath.

BarneyMc

Cavanjack wrote: »

I'm putting in concrete slabs on the first floor and leaving a 200mm cavity below the slab for mhrv ducting.

Is 200mm a standard size for this service cavity? What about the service cavity on the first floor (ceiling below attic) for MHRV, etc.?

Cavanjack

BarneyMc wrote: »

Is 200mm a standard size for this service cavity? What about the service cavity on the first floor (ceiling below attic) for MHRV, etc.?

200mm a little above standard I would say but if MHRV ducting is 150mm you'd need a little extra. Not intending on leaving a service cavity under attic as duct's can come straight down from the attic to each room.

BarneyMc

I was advised to leave a 90mm cavity for a 60mm MHRV duct from a specific supplier. If I don't go with them then maybe I should be allowing for 200mm. Seems like a big jump from 90mm!!

mfceiling

BarneyMc wrote: »

I was advised to leave a 90mm cavity for a 60mm MHRV duct from a specific supplier. If I don't go with them then maybe I should be allowing for 200mm. Seems like a big jump from 90mm!!

A 90mm cavity would be about right for a 60mm duct.

There's no reason to leave a 200mm cavity if you have nothing other than a 60mm duct and a few electric cables.

Maybe if you had a soil pipe (110mm) crossing under a 60mm duct then yes a 200mm cavity would sound correct.

Has anyone told you that you need 200mm? Will you have a suitable ceiling height if you drop down 200mm from your floor slab?

BarneyMc

Leaving a 90mm void would give me an 8.6 feet floor to ceiling height which is not ideal - I believe 9 feet is the magic height for a ground floor?

A 200mm void would leave me with just a 8.3 feet floor to ceiling height which would not be good.

Nobody has told me that I need a 200mm void so I suppose I'll not need it.

sydthebeat

3" is 75mm....not 110??

BarneyMc

sydthebeat wrote: »

3" is 75mm....not 110??

Sorry I might be rounding numbers up/down a bit

Floor to slab height (0 void) = 2726mm = 8.94 feet
Floor to ceiling height (90mm void) = 2636mm = 8.65 feet
Floor to ceiling height (200mm void) = 2526mm = 8.29 feet

I guess the slab is not going to be high enough as it's not giving me 9 feet even without any void.

mfceiling

You don't really need 9ft ceilings to be honest.

8 ft 6 isn't bad at all. I've 9 ft ceilings in my house and i can't think of a single person ever commenting on my lovely high ceilings!!

BarneyMc

mfceiling wrote: »

You don't really need 9ft ceilings to be honest.

8 ft 6 isn't bad at all. I've 9 ft ceilings in my house and i can't think of a single person ever commenting on my lovely high ceilings!!

I've had this conversation here on boards.ie before and it seems like 9 v 8 foot ceilings really do make a big difference, especially in big rooms. I'll speak with my architect about it though.

mfceiling

With a suspended ceiling you can raise/lower your ceiling height to suit each individual room.

What i find is that people tend to "keep it up" in the hall as there are very little services there. In theory if you had a 60mm duct in a room you could have about 90-100mm to the finish plasterboard by using a metal ceiling. Remember then that your finished floor will come up as well.

sas

BarneyMc wrote: »

Sorry I might be rounding numbers up/down a bit

Floor to slab height (0 void) = 2726mm = 8.94 feet
Floor to ceiling height (90mm void) = 2636mm = 8.65 feet
Floor to ceiling height (200mm void) = 2526mm = 8.29 feet

I guess the slab is not going to be high enough as it's not giving me 9 feet even without any void.

My floor to ceiling height is 8ft 7. While I'm sure the 9 foot would be great, we think ours works perfectly well though.

I still think 200 sounds a lot too unless you really need it for a specific reason.