600mm centers for ceiling slab?

Rossdarragh1

Hi there,

I'm currently managing a new build and am looking at my options for slabbing the ceiling. Originally I had planned to use a normal 12.5 plaster slab but my plasterer raised concerns about the joices being 600mm apart. He felt this was too wide and advised me to bridge the joices. The house is 4100 sq. ft and all on the one level. To bridge it would be a considerable cost.

I'm not looking at the option of not bridging it and using 62.5 mm insulated plasterboard on the ceiling. I rang Xtra therm and asked them if 600 mm centers would suffix and they said it would.

The cost difference is not much between the two by the time and factor in labour and timber to bridge the roof. Plus I'd have a better quality product in my ceiling.

I have the ceiling height room to play with and the BER report isn't effected either way as extra roc wool would just be put in attic if going with normal slab. I also don't have to conform to regs as the property was finished to roof level in 2000 and I'm basically completing it. Has anyone any experience of using insulated slab at 600mm centers and were they happy with the result? Cracks , finish etc thanks

sydthebeat

Are you installing an air tight membrane on the ceiling? If not, why not.

When you do that, you can create a service cavity with battens under, with centres to suit

Rossdarragh1

sydthebeat wrote: »

Are you installing an air tight membrane on the ceiling? If not, why not.

When you do that, you can create a service cavity with battens under, with centres to suit

Thanks for the reply. It's a timber frame house. Initially I was putting kingspan board in the external stud walls with an insulated slab over it. In the ceiling I was going with a plaster slab and 400mm rocwool in the joices. I was also going to put in an airtight membrane.This was giving me an A2 rating as per the report.

Since then I've felt that the kingspan card in the walls is not as good a product for timber frame as spaying the studs with open cell beads. Now I'm planning to spray and cover wall with insulated slab leaving out the membrane . In the ceiling as I outlined in my previous post I was advised that a 12.5mm slab would show cracks at 600mm centers if not bridged correctly .

For me to bridge the whole ceiling it with be time consuming and therefore expensive . So I'm looking at using an insulated slab on the ceiling with no bridging of 600mm centers as I was informed the insulated slab would be able for the gap.

I'm then relying on the spray in the perimeter studs to provide a certain level of air tightness along with my insulated slabs on the ceiling . I'll use air tightness tape where possible. I guess I won't be using a membrane after these measures are taken as my budget is pretty tight.

Do you think insulated slabs in the ceiling fixed to 600mm studs would give a good finish to the skimming ?

sydthebeat

Are you installing mhrv?

Bonzo Delaney

Rossdarragh1 wrote: »

Hi there,

I'm currently managing a new build and am looking at my options for slabbing the ceiling. Originally I had planned to use a normal 12.5 plaster slab but my plasterer raised concerns about the joices being 600mm apart. He felt this was too wide and advised me to bridge the joices. The house is 4100 sq. ft and all on the one level. To bridge it would be a considerable cost.

I'm not looking at the option of not bridging it and using 62.5 mm insulated plasterboard on the ceiling. I rang Xtra therm and asked them if 600 mm centers would suffix and they said it would.

The cost difference is not much between the two by the time and factor in labour and timber to bridge the roof. Plus I'd have a better quality product in my ceiling.

I have the ceiling height room to play with and the BER report isn't effected either way as extra roc wool would just be put in attic if going with normal slab. I also don't have to conform to regs as the property was finished to roof level in 2000 and I'm basically completing it. Has anyone any experience of using insulated slab at 600mm centers and were they happy with the result? Cracks , finish etc thanks

Rossdarragh1 wrote: »

Thanks for the reply. It's a timber frame house. Initially I was putting kingspan board in the external stud walls with an insulated slab over it. In the ceiling I was going with a plaster slab and 400mm rocwool in the joices. I was also going to put in an airtight membrane.This was giving me an A2 rating as per the report.

Since then I've felt that the kingspan card in the walls is not as good a product for timber frame as spaying the studs with open cell beads. Now I'm planning to spray and cover wall with insulated slab leaving out the membrane . In the ceiling as I outlined in my previous post I was advised that a 12.5mm slab would show cracks at 600mm centers if not bridged correctly .

For me to bridge the whole ceiling it with be time consuming and therefore expensive . So I'm looking at using an insulated slab on the ceiling with no bridging of 600mm centers as I was informed the insulated slab would be able for the gap.

I'm then relying on the spray in the perimeter studs to provide a certain level of air tightness along with my insulated slabs on the ceiling . I'll use air tightness tape where possible. I guess I won't be using a membrane after these measures are taken as my budget is pretty tight.

Do you think insulated slabs in the ceiling fixed to 600mm studs would give a good finish to the skimming ?

In theory your supposed to have noggins where the slabs meet so the edges are supposed to have solid fixing all around especially at 600 c/c even if it's a 90 mm slab it's a basic enough requirement and a lot more expensive to fix at a later date

Rossdarragh1

Bonzo Delaney wrote: »

In theory your supposed to have noggins where the slabs meet so the edges are supposed to have solid fixing all around especially at 600 c/c even if it's a 90 mm slab it's a basic enough requirement and a lot more expensive to fix at a later date

I guess I could bridge where a slab edge doesn't meet a joice. It's a 62.5mm slab

Rossdarragh1

sydthebeat wrote: »

Are you installing mhrv?

Yes I am along with HP and UF

sydthebeat

Rossdarragh1 wrote: »

Yes I am along with HP and UF

Then you really cannot afford not to install an airtight membrane on the ceiling.

And doing that, you should create a service cavity for your electrics.

The way your doing it now is bad from an airtight point of view, all your electrics will puncture your air tight layer

BryanF

Rossdarragh1 wrote: »

Yes I am along with HP and UF

Don't bother installing a heat pump or putting in ufh unless you make the house air-tight and provide a mechanical vent system. That's a 4000sqft single storey house!!!! Whatever your budget is, you'll pay a fortune in running a heat pump unless you make the place as air-tight as is humanly possible and preferred ease of install should come second to quality and comfort

Rossdarragh1

BryanF wrote: »

Don't bother installing a heat pump or putting in ufh unless you make the house air-tight and provide a mechanical vent system. That's a 4000sqft single storey house!!!! Whatever your budget is, you'll pay a fortune in running a heat pump unless you make the place as air-tight as is humanly possible and preferred ease of install should come second to quality and comfort

Would putting the airtight membrane on the ceiling with the spray in the studs be sufficient from an air tightness point of view? Putting in heat recovery also.

Calahonda52

OP: there is so much wrong with this that I don't know where to start.

Is this a diy/pub mat/labour exchange/ completion job with no professional involvement?

I also don't have to conform to regs as the property was finished to roof level in 2000.

You are profoundly mistaken here.

You may not need to comply with the current energy regulations but you would be a fool not to.

Looking at the chart in the link below you could be paying an extra €7,000 a year in heating bills, based on an area of 380 sq meter, single storey.

http://www.hotfoot.ie/solar-panels-improve-your-ber-rating/

In addition you must meet all the other Building Regs.

One concern I have here is the Fire regs: if the edges of the ceiling slabs are not all fully supported, do you comply with the Fire regs: I don't know, just asking.

There is a requirement to do it along the walls
http://www.gyproc.ie/sites/default/files/Section%206.5%20-%20Timber%20joist.pdf

Without knowing the rest of the material build up in the walls, it is impossible to advise, so whats the make up from outside in, including thicknesses.

In addition can you tighten up the language a bit please:
eg: as spaying the studs with open cell beads

I am not familiar with open cell beads: have you a reference name since you can't post links?

Others have dealt with the ceiling and A/T, whats the plan for electrics etc in the wall?.

How many open fireplaces are there?

mfceiling

Don't screw 62.5mm boards at 600 centres.

They are very heavy and I wouldn't trust them at those centres. 2x2 timbers counter battened at 16 inch centres will be a better job and it won't take that long to do. Much stronger job. When you are screwing them up use 100mm screws with a washer on the end of them and put at least 6 down every run and 7 at the edges.

I'm putting up boards for 16 years and only once have I seen slabs at 600 centres and that was half inch boards above a grid ceiling (was only to keep the noise down from a tin roof above).

BryanF

Rossdarragh1 wrote: »

Would putting the airtight membrane on the ceiling with the spray in the studs be sufficient from an air tightness point of view? Putting in heat recovery also.

not sufficient.

Johnnyhpipe

There are very clear and detailed recommendations for this in the homebond manual.

Rossdarragh1

mfceiling wrote: »

Don't screw 62.5mm boards at 600 centres.

They are very heavy and I wouldn't trust them at those centres. 2x2 timbers counter battened at 16 inch centres will be a better job and it won't take that long to do. Much stronger job. When you are screwing them up use 100mm screws with a washer on the end of them and put at least 6 down every run and 7 at the edges.

I'm putting up boards for 16 years and only once have I seen slabs at 600 centres and that was half inch boards above a grid ceiling (was only to keep the noise down from a tin roof above).

Thanks for the reply. If I had to batten the ceiling I'd probably go back to using a 12.5mm slab and put extra rocwool in the attic to make up for not having an insulated plasterboard. I had a BER assessor look at it and said it would give me the necessary u value.

The only reason I'd put on the insulated slab at 600mm centers is the cost of battening (labour and timber) and the reduction in rocwool in the attic would roughly be the same as putting up insulated slab on the ceiling. I wouldn't put up insulated slab if I still had the cost of battening. Also I'd be reducing ceiling heights between batten and slab.

Thanks for the advice on the screws, didn't think of that. Going putting insulated slab on the walls though. Should all toilets (walls and ceilings) be slabbed with a moisture board? Also do those sound bloc boards perform, have an en - suite backing on to a living room. Going to put acoustic roc wool into internal studs.

Rossdarragh1

Calahonda52 wrote: »

OP: there is so much wrong with this that I don't know where to start.

Is this a diy/pub mat/labour exchange/ completion job with no professional involvement?

I also don't have to conform to regs as the property was finished to roof level in 2000.

You are profoundly mistaken here.

You may not need to comply with the current energy regulations but you would be a fool not to.

Looking at the chart in the link below you could be paying an extra €7,000 a year in heating bills, based on an area of 380 sq meter, single storey.



In addition you must meet all the other Building Regs.

One concern I have here is the Fire regs: if the edges of the ceiling slabs are not all fully supported, do you comply with the Fire regs: I don't know, just asking.

T

Without knowing the rest of the material build up in the walls, it is impossible to advise, so whats the make up from outside in, including thicknesses.

In addition can you tighten up the language a bit please:
eg: as spaying the studs with open cell beads

I am not familiar with open cell beads: have you a reference name since you can't post links?

Others have dealt with the ceiling and A/T, whats the plan for electrics etc in the wall?.

How many open fireplaces are there?

Bought the house 2 years ago. It was built to roof level and slated with windows in but windows were then removed by the previous owner. It had been left idle since 2000. 4000sq ft bungalow. Timber frame. Solid block rising walls with cavity between it and timber frame on internal leaf.

Studs to be sprayed with pro spray ezero E500 foam, along with insulated plasterboard. No open fires, 1 double sided stove and 1 single stove with external air supply.

Electrics, not sure what you mean by this, have a few recessed lights to be sealed along with all powerpoints etc

Rossdarragh1

BryanF wrote: »

not sufficient.

With the studs already up and nailed to the joices I presume each room has to be wrapped individually. Any idea on a cost for that?

BryanF

Rossdarragh1 wrote: »

With the studs already up and nailed to the joices I presume each room has to be wrapped individually. Any idea on a cost for that?

Well that's s balls. You need an air-tightness installer/tester to advise - get 3 quotes