Is it compulsory to use steel in the floor slab under the building regulations?

SRV

<SNIP>

I will begin my build shortly and have a few details im not sure of....


im building a 100 mm block build, simple bungalow with 200 mm cavity. Its 200 msq.
Using a non conducting wall tie....not sure which are available these days?

I want to acheive a very high level of energy efficiency, without going to the level of passive as my budget is quite limited. I believe its not very difficult or expensive to acheive this cheaply, by being super careful with the detail.

Triple glazed 0.8 windows. All windows and doors and joints sealed for airtightness and MHRV used.


Is it compulsory to use steel mesh in the floor slab? This is expensive and if it could be avoided i would prefer. Unfortunately this bungalow is not very compact as its 21 metres long. Long slab. Is the steel to stop cracks and therefore air leaks?


How do i lessen the cold bridge between the floor slab and the inner leaf of the wall? Should i be putting some insulation between the slab and the wall.? If so how much?

I will be allowing the full fill bead to go below the floor level in the cavity.

Is it worth it to use quinnlite blocks on the inner leaf from the foundation up to the floor level?



If i use insulation between the slab and the wall, how do i make the joint airtight?
Do I use a piece of membrane which would be sand/cement plastered to the wall...........and how would this be jointed to the slab?
Whats a clever/cheap detail for this area?


thank you very much

SRV

Mod Edit: any comments for the moderators should be PM'ed directly to the mod and not aired on a thread, it can overtake the thread and drag it off topic, thank you.

alexshinefagan

SRV wrote: »

<SNIP>

I will begin my build shortly and have a few details im not sure of....


im building a 100 mm block build, simple bungalow with 200 mm cavity. Its 200 msq.
Using a non conducting wall tie....not sure which are available these days?

I want to acheive a very high level of energy efficiency, without going to the level of passive as my budget is quite limited. I believe its not very difficult or expensive to acheive this cheaply, by being super careful with the detail.

Triple glazed 0.8 windows. All windows and doors and joints sealed for airtightness and MHRV used.


Is it compulsory to use steel mesh in the floor slab? This is expensive and if it could be avoided i would prefer. Unfortunately this bungalow is not very compact as its 21 metres long. Long slab. Is the steel to stop cracks and therefore air leaks?


How do i lessen the cold bridge between the floor slab and the inner leaf of the wall? Should i be putting some insulation between the slab and the wall.? If so how much?

I will be allowing the full fill bead to go below the floor level in the cavity.

Is it worth it to use quinnlite blocks on the inner leaf from the foundation up to the floor level?



If i use insulation between the slab and the wall, how do i make the joint airtight?
Do I use a piece of membrane which would be sand/cement plastered to the wall...........and how would this be jointed to the slab?
Whats a clever/cheap detail for this area?


thank you very much

SRV

Hi,

I agree with you, I thought my advice was the best and for you to go seek professional advise. I can help you on the other quires you have as they are not structural and are just standard industry details.

Cold bridge between inner wall and slab, as standard practice everybody uses 25mm insulation between the inner wall and edge of slab, the insulation cut to the depth of the slab

Full fill bead - there is no need to let it go below the dpc line, use cavity fill to bring it up to a level, then fill from there, the homebond book has loads of examples of cavity fill, for specifications specific!

Quinlite blocks - as we cant specify on this form, I can just tell you that the most common use of quinnlite block is above dpc level, two courses, the blocks are of no use below dpc, you have limited thermal bridging with your floor insulation and 25mm insulation between slab and inner wall. So its from dpc level up you are concerned.

Air tightness - get professional advice, there are lots of companies out there doing complete packages

SRV

Thanks Alexshinefagan.....the quinnlite blocks above dpc makes sense to me now.
I would prefer more insulation than 25 mm between slab to wall...25 seems too little.

Professional advise can be costly too, and if i can avoid and still do the job correctly i would.

I dont know how the building regs are these days.....i thought putting steel in the slab was an 'extra' that people did to prevent cracking and air leakage through the slab. The hardcore underneath should be compacted according to regulation and therefore slab should not sink. The cracks which might appear are expansion cracks which occur in a large expanse of concrete.....these cracks will affect the airtightness of the build.

My question is ...am i required by regulation to use steel in the slab?

I have figured out how to acheive air tightness in most of the build. The one area i need help with is the slab to wall joint.........this will be affected by the thickness of insulation i use between slab and wall.
Alot of these 'details' have more than one correct way to acheive seal.

appreciate your help

SRV

Bullseye1

The 25mm is only to stop cold bridging. There should also be insulation in the cavity to at least DPC level so you should be okay there.

sydthebeat

i have seldom seen a thread that cries out so much "i have no professional input into my build"...


firstly, your query on reinforcement of a slab is a structural issues and as such will not be allowed by the forum charter... so dont try to chase that one please...

secondly, some of your queries are reuired building regulations.. so i suggest the following:

1. purchase the HOMEBOND house building manual 6th edition... it will have many of your answers

2. check the dept of environment website environ.ie for a list and copy of all the technical guidance documents (building regulations) which have to be met... and technical building details to achieve air tightness and insulation continuity

3 engage a competent professional to answer your queries... in a specific manner... and not just a general manner which we can do here... because i feel that could only lead to more questions...

sydthebeat

Bullseye1 wrote: »

The 25mm is only to stop cold bridging. There should also be insulation in the cavity to at least DPC level so you should be okay there.

the insulation MUST be carried at least 215mm below the dpc line

Bullseye1

sydthebeat wrote: »

the insulation MUST be carried at least 215mm below the dpc line

Yep. There is a good detail in the homebond book.

SRV

sydthebeat wrote: »

i have seldom seen a thread that cries out so much "i have no professional input into my build"...



3 engage a competent professional to answer your queries... in a specific manner... and not just a general manner which we can do here... because i feel that could only lead to more questions...

Hi sydthebeat, thank you so much for your kind bulleted help.


I actually do have professional input, but as has been proven on here numerous times, opinions, and understanding of certain 'detail' can vary greatly. So I asked some questions in an effort to learn from the groups obvious experiance. Now I feel I should'nt ask questions.


SRV

sydthebeat

SRV wrote: »

Hi sydthebeat, thank you so much for your kind bulleted help.


I actually do have professional input, but as has been proven on here numerous times, opinions, and understanding of certain 'detail' can vary greatly. So I asked some questions in an effort to learn from the groups obvious experiance. Now I feel I should'nt ask questions.


SRV

SRV
questions are of course welcomed. however, in order for use to gauge how to respond, with a proper level of technicallity, we need to know what your starting point is. Asking about non conductive wall ties in the same post as asking about how deep your cavity insulation should go shows to me that you are interested but not focused.

posts like "Professional advise can be costly too, and if i can avoid and still do the job correctly i would. " says enough about you for me... i wont be adding anything more this thread...

SRV

I heard about certain wall ties which are less heat conducting than the steel type.
Was curious whether anyone knew of any new certified products on the market?


Dreaming....What a wonderful world it would be if everyone was focused.:)

I would have opinions too but I try not to get too personal.

dos29

I'm using these ones- http://www.qwikfixings.com/glass-fibre-wall-ties.aspx
Far as I'm aware they're certified, and my Engineer is happy to sign off on them.

SRV

Hi Dos 29, thanks for that....those were the type wall ties i was enquiring about.

Alexshinefagan.............i left you a private message....


regards.....SRV

bbam

Definitely get the homebond book..
In relation to the overall budget it costs nothing...

Read, Read and Read and more importantly fully understand the detailing in the book... If you get the detailing in the book right you are well on your way to answering your own questions above..

Surely your engineer who is signing off the build stages and final cert will decide if and how much steel is required in the concrete.. If he is not engauged at this stage how do you expect him to give a final cert if he hasn't seen what the house was built on ??

SRV

I will get a new book.
I had an old version of the Homebond book. They tell me a new version '7' is coming out in october.
Does the book advise on whether two courses quinnlite blocks would lower the cold bridge enough to justify using them. Maybe a glass foam block would be a better option...or some other method. Does it detail areas like the slab to floor joint and the 'various' methods there must be for sealing and reducing the thermal bridge in this area? And what result I might expect from using 4 or 5 inches of insulation instead of 25 mm between the slab and wall. I know the book is essential but i doubt i will learn the answers to the above?.

I have info now on the wall ties thanks to dos 29.


The house is not started yet. I have an engineer who will inspect when the foundations and slab are being poured.
I posted some questions in an effort to learn of other methods of skinning the cat.:)

thanks SRV.

sinnerboy

SRV wrote: »

Does the book advise on whether two courses quinnlite blocks would lower the cold bridge enough to justify using them. Maybe a glass foam block would be a better option...or some other method. Does it detail areas like the slab to floor joint and the 'various' methods there must be for sealing and reducing the thermal bridge in this area? And what result I might expect from using 4 or 5 inches of insulation instead of 25 mm between the slab and wall. I know the book is essential but i doubt i will learn the answers to the above?.

This is where you are stuck - the book won't answer such specific questions . You need to hire someone to perform a thermal analysis of these detials to get these answers .

SRV

Hi Sinnerboy,

I know the book would not provide the info I was looking for. I was looking for ...."oh yeah we used this thickness and we sealed that area using this" etc etc.
I wasnt looking for specifics and exact results...just ideas.

There are various methods of doing a job....and areas like 'for instance' reducing the cold bridge at door thresholds, or how to close a cavity, have been dealt with in various ways by different people. Nothing wrong with learning from others experiances.

Ive learned an awful lot from reading through the posts on various forums where many aspects of structure type and technique were discussed in minute detail....just not happening with this post.

I was even ridiculed for asking about wall ties and cavity insulation in the same post. I didnt realise I was required to keep them seperate.

Anyway I have received some great help and I am grateful to those who helped.:)

regards

SRV

sinnerboy

SRV wrote: »

...just not happening with this post.
SRV

With sincere respect - try to post queries in a more direct manner . Your posts so far a little discursive .

Consider breaking up your queries into different topics and then into different threads - you will get better responses that way .

I am not ridiculing you , I am trying to help you .