Wall ties

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bmcintyre

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A colleague of mine is building a cavity-wall house with a 200mm cavity. Obviously that has big repercussions for certain aspects of the construction but can anyone help me on wall ties.

Where would you get good quality, reinforced wall-ties for a cavity of such a size?

Thanking you in advance.
 
bmcintyre said:
A colleague of mine is building a cavity-wall house with a 200mm cavity. Obviously that has big repercussions for certain aspects of the construction but can anyone help me on wall ties.

Where would you get good quality, reinforced wall-ties for a cavity of such a size?

Thanking you in advance.
Click to expand...

he needs a cavity of that size properly designed and specified by a structural engineer..

under no circumstance should he / she try to do this without professional input!!!
 
just wondering, what is the purpose of the 200mm cavity? i am blocklaying for a good few years and never heard of this
 
manukev said:
just wondering, what is the purpose of the 200mm cavity? i am blocklaying for a good few years and never heard of this
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I expect its for extra insulation. Normal cavities are 100mm. I went for 150mm myself and filled with ecobeads. Getting the wall ties for 150mm was difficult enough so I assume 200mm will be tricky. I would listen to Sydthebeat though, make sure your engineer has reviewed this plan.
 
What I would do instead of a wider cavity but would cost more is put an insulated slab on the inside of all the outside walls.
This way the heat never gets to the block never mind the cavity and you will not have any cold walls.
I did it and i find the house heats up very quickly because none of the heat is lost heating up the block.
 
sydthebeat said:
he needs a cavity of that size properly designed and specified by a structural engineer..

under no circumstance should he / she try to do this without professional input!!!
Click to expand...
That's all in order.

He's just trying to source the proper wall ties and his engineer isn't entirely sure as he hasn't had to source them before.
 
"I did it and i find the house heats up very quickly because none of the heat is lost heating up the block."

The opposing view to this is that the inner leaf of blockwork acts as a sort of heat sump - yes it will heat up quicker, but it will also cool down quicker.

That said, I imagine that for modern living, where people are out most of the day with the heating on a timer, a house which heats up quickly is probably more useful than one which maintains its heat more easily.
 
bmcintyre said:
A colleague of mine is building a cavity-wall house with a 200mm cavity. Obviously that has big repercussions for certain aspects of the construction but can anyone help me on wall ties.

Where would you get good quality, reinforced wall-ties for a cavity of such a size?

Thanking you in advance.
Click to expand...

[broken link removed]

If it's a single story house, your friend should be fine with a 100mm inner leaf block, but if it's two story he'd probably be better off with a 215mm inner leaf with a 100mm outer leaf. Make sure the engineer designs the specification for the foundations.

Hope this helps.
 
I don't think a 200mm cavity complies with the building regulations - I could be wrong, because I've never specified one.

At that width I think you're taking multibeam purlins, not wall ties :)

Get a competent building professional to review youre entire house, because if you're not so clued in about max. cavity widths, odds are there are other things amiss.

HTH

ONQ.
 
onq said:
I don't think a 200mm cavity complies with the building regulations - I could be wrong, because I've never specified one.

At that width I think you're taking multibeam purlins, not wall ties :)

Get a competent building professional to review youre entire house, because if you're not so clued in about max. cavity widths, odds are there are other things amiss.

HTH

ONQ.
Click to expand...

You're right - an Arch told me this a few month's ago too - that cavities over 150mm weren't approved, and that there's no approved tie. In fact, as someone pointed out, even a 150mm tie is difficult to get.

Brings up other issues too .........foundation width's.........cavity cap at top (cavity closer block won't work........).....
 
ITS NOT THAT THEY 'DONT COMPLY' WITH THE REGS... (oops pardon the caps!)

its that they are not 'prima facia' covered by the regs.

Once the design is structurally designed and certified to comply with I.S.
325: Part 2: 1995, and ancillary components comply with BS 845, then it shall comply with teh regs.
 
sydthebeat said:
ITS NOT THAT THEY 'DONT COMPLY' WITH THE REGS... (oops pardon the caps!)

its that they are not 'prima facia' covered by the regs.

Once the design is structurally designed and certified to comply with I.S.
325: Part 2: 1995, and ancillary components comply with BS 845, then it shall comply with teh regs.
Click to expand...


Syd,

I haven't a clue what all that means because i haven't actually read all the standards you refer do [certainly not in a while - 1995?].

If all these standards seem to be saying "if a structural engineer says its okay, its okay" I'm not so certain that it is. Its possible to prove something can theoretically can carry a load, but it can still fail a stability test.

Take note that I am not an engineer so take all that I say about structures with that one on board.

But in relation to 300mm cavity walls 100/100/100 I was speaking to an engineer about this only on Thursday of last week.

I had posed the question in a theoretical way stating that the ties always acted in tension as they had a vary narrow section and therefore negligible compressive strength and I was wondering how they contributed to the strength of the cavity wall.

He told me that empirical tests have been undertaken in relation to a 100mm inner leaf where this was loaded for a normal two storey house load, with and without an outer leaf bonded to it with wall ties.

The load bearing capacity was not the issue. i.e. the crushing strength of the masonry was adequate. The failure of the leaf occurred at higher loads due to the buckling of the wall due to lack of lateral restraint. The wall ties, even acting in tension alone, provided sufficient lateral restraint so that the inner leaf could take a higher load.

Now apply this - if we can - to the present case.

I suspect that widening the cavity but still with relatively thin ties may lessen the lateral restraint available. I think this might need a test to determine it fully. I think either you'll end up using something like a 200mm multi-beam purlin vertically, or your ties will end up being 6mm s/s sections with a twist for a cavity drip and splayed ends for building in, much like the old galvanised pressed metal ties.

AND WATCH THOSE CAPS!!!

:)

ONQ.
 
onq said:
Syd,

I haven't a clue what all that means because i haven't actually read all the standards you refer do [certainly not in a while - 1995?].

If all these standards seem to be saying "if a structural engineer says its okay, its okay" I'm not so certain that it is. Its possible to prove something can theoretically can carry a load, but it can still fail a stability test.

Take note that I am not an engineer so take all that I say about structures with that one on board.

But in relation to 300mm cavity walls 100/100/100 I was speaking to an engineer about this only on Thursday of last week.

I had posed the question in a theoretical way stating that the ties always acted in tension as they had a vary narrow section and therefore negligible compressive strength and I was wondering how they contributed to the strength of the cavity wall.

He told me that empirical tests have been undertaken in relation to a 100mm inner leaf where this was loaded for a normal two storey house load, with and without an outer leaf bonded to it with wall ties.

The load bearing capacity was not the issue. i.e. the crushing strength of the masonry was adequate. The failure of the leaf occurred at higher loads due to the buckling of the wall due to lack of lateral restraint. The wall ties, even acting in tension alone, provided sufficient lateral restraint so that the inner leaf could take a higher load.

Now apply this - if we can - to the present case.

I suspect that widening the cavity but still with relatively thin ties may lessen the lateral restraint available. I think this might need a test to determine it fully. I think either you'll end up using something like a 200mm multi-beam purlin vertically, or your ties will end up being 6mm s/s sections with a twist for a cavity drip and splayed ends for building in, much like the old galvanised pressed metal ties.

AND WATCH THOSE CAPS!!!

:)

ONQ.
Click to expand...

you are correct in that the majority of ties that comply with bs 845 for cavities in excess of say 100 mm are vertical twist ties and not the 'butterfly' ties we are used to.

im not quite sure i can accept this statement "Its possible to prove something can theoretically can carry a load, but it can still fail a stability test." Engineers do this all the time, and include variables in the calcs to protect against failure. Then obviously certify this element of construction to indemnify its suitability.
 
sydthebeat said:
you are correct in that the majority of ties that comply with bs 845 for cavities in excess of say 100 mm are vertical twist ties and not the 'butterfly' ties we are used to.
Click to expand...

<nods>

Thanks for confirming that - I recalled those kind of wall ties seemed to have a bit of compressive strength.

im not quite sure i can accept this statement "Its possible to prove something can theoretically can carry a load, but it can still fail a stability test." Engineers do this all the time, and include variables in the calcs to protect against failure. Then obviously certify this element of construction to indemnify its suitability.
Click to expand...

Ah that's just me being pedantic.

I was referring to the ability of an engineer to certify structure within a narrow focus - this can sometimes be a very useful trait ;)

As I may have mentioned in another post, they only certify to Part A, Structure, and I have never been able to draw one [sic] on certifying a piece of structure has the required Fire Rating.

ONQ.
 
Hi guys I was reading your posts and i know there is a company in Limerick making ties of this size for cavities over 100mm. they are Shannon Coiled Springs on the Ballysimon Road. They make Ties to suit cavities from 100mm to 300mm
 
ONG, this company is certified to manufacture wall ties of all sizes. They are the largest manfacturer of ties in Ireland.
 
mikeymull

First: its ONQ, not ONG and no, you're not the first :)

Second: none of that is immediately apparent from their website - how do you know so much about the company - do you have a connection?

ONQ.
 
Hi guys,

Im just reading over the above post and im wondering if someone could please clarify if the 200mm cavity goes against building regs??

bmcintyre -
how did your friend get on with his 200mm cavity build had he problems with founds/wall ties/cills or closing the cavity??

i personally think its easier and cheaper to increase the cavity to 200mm than to fix insulated slab to the internal permieter wall - any one any thoughts?
 
Regarding the structure of buildings, the relevant guidance is given in Part A of the Second Schedule of the 1997 Building Regulations. It is important to note that the Building Regulations state in general terms what the requirements are, for example Part A basically states that the building should be stable, and should be able to accept and transfer all loads imposed on it without collapse or deflection. This is the law.

The TGD’s are only there to offer guidance regarding how to complying with the law. They are not ‘law’, and can be ignored if another way of meeting the requirements of the relevant building regulation can be used and certified.
The Building Regulation is quoted at the front of Technical Guidance Document (TGD) A of 1997, link as follows:
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1639,en.pdf

The relevant guidance from the TGD document is as follows:
1.1.3.4 Wall Construction
External walls
(a) Cavity walls constructed using two leaves composed of either, solid concrete blocks or bricks of not less than 100 mm thickness, or of clay bricks, tied together with wall ties appropriate to the width of cavity. The inner leaf may be constructed using 100 mm thick lightweight solid concrete blocks.

So the width of the cavity is not specified, as long as the wall ties are ‘appropriate’ to the cavity width.
 
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