Cavity Closer at Eaves/top of wall

Tom Hagen

hi guys,

Just looking for any opinions on the best way for closing the cavity at roof level.

my engineer says use a 'thermal block cavity closer' basically a large quinnlite to bridge the 150mm cavity and that sits on both 100mm leaves to prevent thermal bridging. my wall plate will be secured to this.

Some blocklayers say a quinnlite block is too 'soft' really for that job. the full strength of a quinnlite is when its Layed on edge.

Could I use a concrete cavity closer and use an insulated slab on the inside ceiling to prevent thermal bridging?

I'm pumping the cavity. and not running the insulation all the way continuously into roof like I see in some detail.

sydthebeat

http://www.kilsaran.ie/build/product/thermal-lightweight-block/

use this instead

Tom Hagen

I also meant to add. I'm building the last course at the top with standard 4 inch quinnlites all around the house. do I need a thermal cavity closer with this aswell

sydthebeat

Tom Hagen wrote: »

I also meant to add. I'm building the last course at the top with standard 4 inch quinnlites all around the house. do I need a thermal cavity closer with this aswell

why would you do that? do you not have cavity insulation?

the cavity closer is your engineers requirement, so s/he has determined already that its needed

Tom Hagen

sydthebeat wrote: »

why would you do that? do you not have cavity insulation?

the cavity closer is your engineers requirement, so s/he has determined already that its needed

pumped cavity ya. the last course at the top internal leaf will be quinnlite just as double protection for thermal bridging. just wondering if I use a concrete cavity closer will that last course protect me from thermal bridging?

engineer is open to other suggestions from the client if they are feasible and will comply.

sorry if this seems stupid questions

sydthebeat

Tom Hagen wrote: »

pumped cavity ya. the last course at the top internal leaf will be quinnlite just as double protection for thermal bridging.

1. just wondering if I use a concrete cavity closer will that last course protect me from thermal bridging?

2. engineer is open to other suggestions from the client if they are feasible and will comply.

sorry if this seems stupid questions

theres no stupid questions, only stupid answers

1. Technically no, it wont add anything towards thermal bridging as the bridge is already broken by the pumped cavity. If anything it would make matters worse as it creates a clear definitive line internally between 'super insulated' (quinlite/pumped cavity/quinnlite) and poorly insulated (cavity closer). personally i would use teh kilsaran block and keep the blockwork homogenous under. The quinnlite (or kilsarans thermal block) have much more significant impact at floor level.

2. i wouldt see it as the clients position to offer different methods of construction. The engineer should be able to offer you a range of options and divide them of basis of cost, impact, buildability etc. The blocklayer might also offer options depending on experience.

Calahonda52

Tom Hagen wrote: »

.... and not running the insulation all the way continuously into roof like I see in some detail.

If not then, are you still complying with the 2011 ACDs
http://www.housing.gov.ie/sites/default/files/migrated-files/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad%2C18751%2Cen.pdf

How exactly is the cavity closer (cc) going to work?
10 plus 150 plus 100 = 350 ?
will cc be a trimmed block run across?
Then you are sitting the wall plate on it: inside face, outside face, middle, where.
How is wall plate being fixed?
...
Copyright in attachment acknowledged
he first link is for details, second for Irish pricing
https://www.amazon.co.uk/Construction-Technology-Designing-Sustainable-Homes/dp/0717148343/ref=sr_1_fkmr1_1?ie=UTF8&qid=1463079029&sr=8-1-fkmr1&keywords=construction+technology-+trevor+hockey

https://schoolbooks365.ie/index.php?_route_=construction_technology_hickey

Tom Hagen

sydthebeat wrote: »

theres no stupid questions

1. Technically no, it wont add anything towards thermal bridging as the bridge is already broken by the pumped cavity. If anything it would make matters worse as it creates a clear definitive line internally between 'super insulated' (quinlite/pumped cavity/quinnlite) and poorly insulated (cavity closer). personally i would use teh kilsaran block and keep the blockwork homogenous under. The quinnlite (or kilsarans thermal block) have much more significant impact at floor level.

2. i wouldt see it as the clients position to offer different methods of construction. The engineer should be able to offer you a range of options and divide them of basis of cost, impact, buildability etc. The blocklayer might also offer options depending on experience.

ya I have the first course at floor level built up with quinnlites. food for thought with the cavity closer issue. have a bit of time yet.
thanks

Tom Hagen

sydthebeat wrote: »

theres no stupid questions, only stupid answers

1. Technically no, it wont add anything towards thermal bridging as the bridge is already broken by the pumped cavity."

quick question syd what do you mean by the thermal bridge is already broken by pumping the cavity?
does that mean my entire house has no thermal break from the cold outside leaf

sydthebeat

Tom Hagen wrote: »

sydthebeat wrote: »

theres no stupid questions, only stupid answers

1. Technically no, it wont add anything towards thermal bridging as the bridge is already broken by the pumped cavity."

quick question syd what do you mean by the thermal bridge is already broken by pumping the cavity?
does that mean my entire house has no thermal break from the cold outside leaf

thermal bridges occur at junctions (mainly) ie where floors meet walls, where walls meet roofs etc

your detail where the wall meets the roof includes (at the moment) a cavity closer which is a block which spans from the internal, across the cavity, to the external, in effect breaking the insulation envelope. This is a thermal bridge.
This thermal bridge is reduce by using a thermal block, but its still a thermal bridge (the material in the thermal block is approx 9 time worse than your insulation at keeping in heat.... if you use a standard block it would be almost 30 times worse)

where you are planning on using the quinnlites, you dont have anything breaking the insulation envelope.. therefore there isnt a thermal bridge there, therefore the use of quinnlites at that location is unnecessary as they arent really stopping any significant heat loss.

Tom Hagen

sydthebeat wrote: »

theres no stupid questions, only stupid answers

1. Technically no, it wont add anything towards thermal bridging as the bridge is already broken by the pumped cavity. If anything it would make matters worse as it creates a clear definitive line internally between 'super insulated' (quinlite/pumped cavity/quinnlite) and poorly insulated (cavity closer). personally i would use teh kilsaran block and keep the blockwork homogenous under. The quinnlite (or kilsarans thermal block) have much more significant impact at floor level.

2. i wouldt see it as the clients position to offer different methods of construction. The engineer should be able to offer you a range of options and divide them of basis of cost, impact, buildability etc. The blocklayer might also offer options depending on experience.

sydthebeat wrote: »

Tom Hagen wrote: »

thermal bridges occur at junctions (mainly) ie where floors meet walls, where walls meet roofs etc

your detail where the wall meets the roof includes (at the moment) a cavity closer which is a block which spans from the internal, across the cavity, to the external, in effect breaking the insulation envelope. This is a thermal bridge.
This thermal bridge is reduce by using a thermal block, but its still a thermal bridge (the material in the thermal block is approx 9 time worse than your insulation at keeping in heat.... if you use a standard block it would be almost 30 times worse)

where you are planning on using the quinnlites, you dont have anything breaking the insulation envelope.. therefore there isnt a thermal bridge there, therefore the use of quinnlites at that location is unnecessary as they arent really stopping any significant heat loss.

ah yes I see now. much appreciated.

I think I'm trying to tell myself that the quinnlite block on the top course under the cavity closer block will prevent any Cold conductivity from the cold roof/cavity closer conducting down into the internal wall structure. so having a quinnlite at floor level and at eave level the blocks in between should be somewhat separated from cold bridges.
is there anything to be said for that?

sydthebeat

Tom Hagen wrote: »

the quinnlite block on the top course under the cavity closer block will prevent any Cold conductivity from the cold roof/cavity closer conducting down into the internal wall structure.

well no, because the cavity closer block will be exposed to the internal rooms

heat will travel from the warm room to the cold outside... and by the route of least resistance.



as you can see from the pic above... the two blocks under the cavity closer dont do anything to stop the heat loss

kerry bhoy

This is what I did.

Tom Hagen

kerry bhoy wrote: »

This is what I did.

where did your wall plate sit then? ..looks nice and tidy job in fairness.

kerry bhoy

Double wall plate on outside leaf

PATJOE

kerry bhoy wrote: »

Double wall plate on outside leaf

Have you any pics of the wall plates fitted?

kerry bhoy

It's not a close shot but you can still make it out.

BryanF

Thermal bridge details at wall/floor slab, internal rising walls, window Cill and air-tightness at wall plate

Tom Hagen

kerry bhoy wrote: »

It's not a close shot but you can still make it out.

nice view lad , thumbs up. should be great view from upstairs

Tom Hagen

kerry bhoy wrote: »

It's not a close shot but you can still make it out.

Kerry bhoy, any tips on roofing? my roofer should be on-site soon. did you shop around different suppliers for the materials? how long did it take him to Joist it off? looks tidy work.

kerry bhoy

Hi Tom, just make sure your roofer is tried ,tested and trustworthy then let him call the shots.think it took about 3 weeks or so to finish joists.definitely price around.3 suppliers if possible,let the first shop quote you then take that to no 2 and if they beat no 1 then go to no 3 and then back around again until you are told piss off.my First quote was 24000 including facia and sofit and after wrecking suppliers heads for about 2 weeks I ended up paying 21900.shop around for everything if you have the patience.

Duffyorkie

I was in America for years and cavity closing was not an issue. I am now building here and it is like the unanswered question everywhere with engineers architects and builders in general everyone has there own theory. Here is my 2cents on the topic. Eg. 100mm inner and outer leaf of block with 150mm full cavity insulation. use timberlocs to bolt wall plate to 9x2 from underside express nail 9x2 to inner leaf and outer leaf thus spreading the load. tack ridged insulation to inside of both timbers and with timber also being an insulator should minimise but not eliminate cold bridging. Open to all other suggestions and comments.

MacConmhaigh

Hi all, I am new to this forum lark but have an interest in this thread as i am building a house for the second time unfortunately!! my cavity wall is standard 100/150/100. i am concerned about the strength of the wall plate level when the roofer begins. in my last build i placed a six inch cavity closer on top of cavity and this gave it good support for roof. i had to do a bit of insulating and expanding metal for plasterer but this was no biggy.as far as i could see there was no issue with damp etc coming in through the 'thermal bridge'. i lived in the house for ten years until last year and it was a grand warm house even for 2006/7 standards of insulation. I would love to hear your opinions on strength and not thermal bridging on the cavity closer if anyone has any. thanks in advance.
macconmhaigh

Metric Tensor

When you think about what a cavity closing block actually does ....

It joins the two wall leafs at the top - the wall ties do this job everywhere else and in theory if the rafter spans the cavity it can do the same thing.

The wall plate is usually fixed to the inside of the cavity closer block so the load was transmitted to the inner leaf - as it continues to be in the absence of the cavity closer.

So I would ask (I'm not saying I have the answer): Although the block spanning the top of the cavity made the wall appear more solid was it actually doing a whole lot more than acting as a glorified wall tie?

MacConmhaigh

Hi Metric Tensor,
Thanks for reply. The block closer is possibly a more secure 'wall tie'?? it is preventing the two walls leafs from being disturbed on the top most block? in the event a block on this level got a belt off a timber plank etc? if not a closer block the force of plank would knock off the block or damage the integrity of it.
anyways i agree the wall ties do secure the walls every where else along the build. It may be just a traditional thing thing that i want one! However my engineer has specked a wall plate on both inner and outer leaf. how does this sound in your opinion/experience?
All i know about building is what i did before so i am NO expert at all.

Metric Tensor

Wall plate on inner and outer leaf each separately secured to the rafter or joist is becoming quite a common detail these days. Essentially using the rafter or joist to do the same job as the closer block used to do.

This arises out of the Acceptable Construction Details issued with Part L of the Technical Guidance Documents - which were written with no regard whatsoever for structural robustness - so engineers and technicians have had to reinvent structural details on the fly!

MacConmhaigh

What would your judgement be on two wall plates over traditional block closer?

Metric Tensor

You will have big problems showing compliance with the building regulations via the thermal bridging factor in DEAP if you use a traditional block closer!

So my opinion is coloured by that.

When the closer blocks first started losing favour 5-8 years ago I was very against the change but with newer wider cavities and better thermal bridging details I've made my peace with no cavity closer block and as above on a somewhat quick and dirty engineering analysis I'm not sure the closer block was doing a whole lot structurally in the first place. Although this may vary from design to design and your engineer is the only one that knows your house well enough to talk about it directly.

Except in some unusual situations the outer leaf of the cavity is predominantly a rain screen. Also - Timber frame houses, with blockwork outer leaves have been built here since the 90s and never had a concrete closer block.

MacConmhaigh

Ok mo chara, thanks for the advice, I'm sure ill be back again!!!

saltandpepper10

The roof in that picture looks to have serious triangularisation issues to me