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Walltite - certification for masonry cavity retrofit

Lumen

There have been many threads on closed-cell PU foam (specifically Walltite) including retrofit insulation of masonry cavity walls (which is what I've considered for my own house), but none of them really closed the loop on the certification situation.

Many of the installer websites are misleading in that they state that the product is certified, but don't make it clear for what application and under which conditions. This is really critical.

So here is my attempt to pull together the objective facts and then try to interpret them.

Disclaimer: I am not a construction professional, just a punter.

There are two current Walltite products that are similarly named: CV 100 and CL 100. I think CL 100 is used for surface applications, whereas the CV 100 product is the one offered for cavity retrofit, presumably because it is slower to expand and therefore fills better and poses less risk of pushing the leaves apart. I have found references to other Walltite products (e.g an Eco product which uses/used "polyols from castor oil") but I don't know whether they're still sold.

The only NSAI cert for Walltite is :

Cert No. 13/0377 (26/04/2013)
https://www.nsai.ie/Our-Services-(1)/Certification/IAB130377_GOS_BASF.aspx

This cert slightly pre-dates the BBA certification. It also (irritatingly) isn't very specific about which product is certified, only "BASF Walltite Spray foam insulation". In any case, it DOESN'T cover retrofit cavity installation. Maybe this is because only CL 100 was submitted for certification.

The BBA certs are listed on the Walltite website:

http://walltite.basf.ie/downloads/bba-certification

...but I'll link to the versions on the BBA website.

BBA Certificate No. 13/5002 Product Sheet 1 (20/05/2013), WALLTITE® CV 100 Cavity Wall Insulation
http://www.bbacerts.co.uk/CertificateFiles/50/5002PS1i1.pdf

BBA Certificate No. 13/5002 Product Sheet 2 (20/05/2013) - WALLTITE® CV 100 Cavity Wall Insulation & Stabilisation
http://www.bbacerts.co.uk/CertificateFiles/50/5002PS2i1.pdf

Note that these are just different product sheets and share the same certification number and date.

I'll skip over the stabilisation certification except to note that since it's the same product in the same application (but differing conditions), it's reasonable to assume that when applied in a cavity wall with functioning wall ties it won't shrink or degrade over time, and is likely to stay bonded to the masonry surface and thus prevent thermal looping, otherwise it wouldn't have certification for holding a wall with corroded ties together for 25 years, as stated in section 12 of the second certification:

The product is unaffected by the normal conditions in a wall and is durable, rot proof, water resistant and sufficiently stable to remain effective as a replacement for wall ties for at least 25 years.

However, going back to the first BBA cert, the caveats for use are many but these are particularly noteworthy:

This Certificate covers the use of the product in any exposure zone(1), subject to the following conditions being met, which are particularly important in areas which may experience severe or very severe driving rain:
• a site survey should be carried out prior to installation (see sections 13 and 14).
• the minimum cavity width must be not less than 40 mm
• walls must be in good state of repair and show no evidence of frost damage
• mortar joints must not show evidence of more than hairline cracking. Raked or recessed mortar joints should be avoided in very severe exposure areas

...

Walls will limit the risk of surface condensation adequately when the thermal transmittance (U value) does not exceed 0.7 W·m–2·K–1 at any point and the junctions with floors, roofs and openings are designed in accordance with Limiting thermal bridging and air leakage : Robust construction details for dwellings and similar buildings (TSO 2002), IP 1/06 or section 6.3 of this Certificate.

I've included references to some of these standards below, but they are complicated. The upshot is that the product is not suitable unless your house is built properly and the walls are good shape already (apart from the wall ties).

References:

Limiting thermal bridging and air leakage : Robust construction details for dwellings and similar buildings (TSO 2002)
http://draught-finder.co.uk/wp-content/uploads/2017/01/Limiting-thermal-bridging-and-air-leakage-Robust-construction-details-for-dwell-02.11.2015.pdf

Section 3, Robust Details - Masonry: Cavity Wall Insulation: Full-Fill, starts at page 37 and includes details such as continuity of cavity and attic/roof insulation.

BS 5250:2011 Code of practice for control of condensation in buildings (+A1:2016)
I can't find a free PDF of this but the Abstract is available, e.g.
https://www.thenbs.com/PublicationIndex/documents/details?Pub=BSI&DocID=314968

There's an older version (BS 5250:2002) here:

https://www.aecb.net/wp-content/plugins/aecb-carbonlite-knowledgebase/librarian.php?id=11197&file=11198

Now I'll try and unpick/translate the above.

Since this insulation product is not breathable, and fully fills the cavity (or remainder of the cavity, if rigid partial fill is already present), you may get problems with interstitial condensation or moisture build up if:

1. Poor quality render or roof detailing is allowing rain to penetrate. I believe that rendered concrete block (in good condition) is much less permeable than brick - there are a lot of brick houses in the UK so maybe is less of a concern in Ireland; in any case my specific interest is block construction.

2. There is significant cold bridging. This gets worse if you live in a cold climate, see that the caveats in the BBA cert give different required U-values for Scotland (1.2 W·m–2·K–1) and not-Scotland (0.7 W·m–2·K–1). That said, it's possible that the product helps with certain types of cold bridging, e.g. joists going through the inner leaf without proper sealing might be less of a problem with a warm inner leaf. I can't work out whether this is the U-value BEFORE or AFTER the product is installed.

3. You already have issues with air tightness, as in that case you may get moisture hitting the inner side of the insulation. This is ironic since the product is promoted (but not certified for) helping solve air tightness problems. But maybe this isn't a problem since this is the warm side of the insulation and so the vapour won't condense or penetrate further?

4. The insulation isn't installed properly, which isn't as simple as drilling holes and pumping in correctly mixed product - the interfaces to other parts of the building fabric are important.

I suppose the most serious problem with moisture is if it collects around the wall ties leading to corrosion. If that happens you're relying on adhesion to the brick to stabilise the wall, which seems implausible...except that case is specifically covered by the second certification. Nonetheless, the prospect of destabilising a perfectly good wall by adding insulation is off-putting.

This recent Technical Update from the NSAI on the subject of retrofit cavity insulation is also interesting/possibly relevant:

Technical Update: A Periodical for Approved Installers of ETICS and CWI, January 2016
https://www.nsai.ie/Our-Services-(1)/Agrement/Cavity-Wall-Installer-Documents/CWI-ETICS-Technical-Update-Issue-1.aspx

This covers Borescope Inspections, ventilation checks, checks for isolation of electrical cables, inspection of the top of the cavity etc. It also emphasises the need for installers to keep records of these activities.

Since NSAI hasn't certified any PU closed cell foam for this application (AFAIK), this guidance was presumably written with beads in mind, but most of it is probably also relevant for PU foam.

The takeaway is: there's a lot to get right here and the details are difficult for a non-professionals; do you trust the installers to follow the certification conditions to the letter? This is so important to get right since there is no "undo" on this type of insulation (or bonded bead for that matter). You get one shot.

Maybe there's a case for on-site supervision (or at least verification of the pre-install survey elements) by an independent arch tech/engineer?

For my own application I'm still weighing up the pros and cons.

I've seen it posted that buildings insurance won't cover non-certified products. Assuming that this is an issue, has anyone here asked their insurer whether BBA is sufficient?

Obvs. you could rely on the liability insurance/warranty provided by the installer, but that would be...brave.

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Lumen wrote: »

There have been many threads on closed-cell PU foam (specifically Walltite) including retrofit insulation of masonry cavity walls (which is what I've considered for my own house), but none of them really closed the loop on the certification situation.

What did you go with in the end Lumen?

I am considering my options at the moment.

Lumen

S' wrote: »

What did you go with in the end Lumen?

I am considering my options at the moment.

Nothing yet! Need to get it sorted before winter.

But I think I'll go with beads. Everyone I've asked with an engineering qualification thinks it's safer.

I'll save my bravery for projects that can be undone.

Lumen wrote: »

I'll save my bravery for projects that can be undone.

Ha! I'm thinking the same. Would like to use this product but so worried it may cause issues down the line.

Calahonda52

Good work Lumen

My lifelong concern with this stuff, especially the foam is how do you know that the stuff they pump in is the certified stuff or even closed vs open cell as required
I am less uncomfortable with the beads, but none of this stuff gives me a warm feeling

caesarthechimp

Have these wall ties already been diagnosed as being corroded?
I'd assume that only a sprayfoam would have some ability to hold the two leafs together, unlike a bonded bead. I don't see how a closed cell sprayfoam could "collect" moisture around a wall tie. If there was some chemical reaction between the foam and the metal, that is different matter, and should be mentioned in the cert.
The CV100 is marketed as closed cell. Its a purple colour, whereas the more common sprayfoams seen in attics may be greenish or white and may be open cell and breathable/water vapour permeable.

The CV100 is going to be 2 or 3 times the price of bonded bead, but in theory will provide better insulation for the same thickness of cavity. But as pumping a cavity is the cheapest way to insulate a wall anyway, the cost of the actual material itself should not be seen as a deal-breaker.

For a cavity wall you want something that will not wick (rain)water from the outer leaf. Bonded EPS bead is known to be good. Closed cell is newer and should be good (according to the BBA cert) Open cell foam... not so much. Another thing you can do here is to keep the outer leaf drier. Make sure gutters are not overflowing or dripping. If the wall is facing southwest towards driving rain, and there is not much of an overhanging soffit, you can apply a water seal coat or a water resistant masonry paint to the most exposed wall.

The interstitial condensation thing refers to water vapour going in the opposite direction, from inside the house towards the outer leaf. As you pointed out, if it is closed cell, and is virtually impermeable, then the vapour cannot get past the warm side of the insulation and so will not reach its dew point, and will not condense.

If there are a lot of thermal bridges (maybe around lintels and cills, or at the top of the cavity where it is closed by a bridging block laid on the flat) then the foam cannot insulate these. After the insulation is completed, these areas might attract more condensation than before. This could manifest as the black mould that is sometimes seen from inside rooms of the house. But that happens because these small areas are relatively more cold than the rest of the wall. Reduce this by more room ventilation, and stop drying clothes on the radiators, and use extractor fans in kitchen and bathroom "wet rooms".

Lumen

caesarthechimp wrote: »

I don't see how a closed cell sprayfoam could "collect" moisture around a wall tie

It depends on how well the foam seals around the wall tie. I know that a solid, thick layer of PU foam is airtight, but what's to stop humid air from travelling outwards along the junction between the tie and the foam? Is it really that airtight in practical applications where it's injected blind through drilled holes?

In any case, steel wall ties are a cold bridge, so the inner end of the tie is going to be the coldest element at that inner foam/wall interface. Surely there's a condensation risk there, in the absolute worst place for it?

From a certification perspective, the issue is that the BBA cert is specifically oriented around an application where wall ties are already compromised, in which case the purpose of the foam is to replace the function of the wall ties by bonding the leaves together, so there wouldn't be a concern about further corrosion.

But what about the case where the wall ties were fine before the foam?

Wartburg

Lumen wrote: »

Is it really that airtight in practical applications where it's injected blind through drilled holes?

As I already wrote in another thread, I have to confirm the air tightness of BASF walltite CV 100 after doing a provisonal air tightness test in a new build, where the foam was used earlier this year. I´m usually not a big supporter of these chemical panaceas and do not have any relation to BASF or an installer as well.
I couldn´t imagine to use Walltite for an existing building, because of the more difficult installation method in comparison to beads. There is drilling involved that turns the walls in the same shape like a swiss cheese. Furthermore it needs to be installed separately for every block row. The biggest concern I have is about the bonding/ reaction between Walltite and the 50mm polystyrene, the most newer houses got installed to the inner leaf in the cavity.

caesarthechimp

Lumen wrote: »

It depends on how well the foam seals around the wall tie. I know that a solid, thick layer of PU foam is airtight, but what's to stop humid air from travelling outwards along the junction between the tie and the foam? Is it really that airtight in practical applications where it's injected blind through drilled holes?

Yes, it is really that sticky. Have you ever tried to clean sprayfoam off your fingers?

In any case, steel wall ties are a cold bridge, so the inner end of the tie is going to be the coldest element at that inner foam/wall interface. Surely there's a condensation risk there, in the absolute worst place for it?

It just means the wall tie is colder at one end than the other. At the warm end of the tie, it is slightly colder than the inner leaf which it is embedded in. However you can't get condensation building up inside a bone dry bed of mortar.

From a certification perspective, the issue is that the BBA cert is specifically oriented around an application where wall ties are already compromised, in which case the purpose of the foam is to replace the function of the wall ties by bonding the leaves together, so there wouldn't be a concern about further corrosion.
But what about the case where the wall ties were fine before the foam?

Well there you go, you apparently don't need the ties afterwards anyway.
Maybe somebody should pass this info to the guys who built those schools that have been in the news recently, you know, the ones where they forgot to put in the wall proper ties at the time. Ask BASF if their product sticks timber frame walls back together again, like Humpty Dumpty.

caesarthechimp

Wartburg wrote: »

The biggest concern I have is about the bonding/ reaction between Walltite and the 50mm polystyrene, the most newer houses got installed to the inner leaf in the cavity.

Is there any evidence for this though? You could easily test it for yourself by spilling some of the BASF foam onto a spare piece of EPS board, just lying in the ground. If it doesn't do anything in the first few seconds it probably won't ever react.
Some of the fears about these things come from practical experience with various other products eg gunoprene adhesive will dissolve EPS insulation boards quicker than a Saudi ambassador gets rid of a journalist, but silicone is fine on the same board.
When in doubt, try it out (on a small sample)
In some of the certs for various foams, there is a figure showing "reacts with zinc" (usually shown as miniscule). This would be relevant with galvanised ties. But most builders have been using stainless steel for years now. Some have used also basalt (teplo ties) and glass fibre ties instead of steel to reduce thermal bridging.

I reckon carbon fibre would be the ideal material - warm and with very high tensile strength. Never seen them though.

Lumen

Wartburg wrote: »

I couldn´t imagine to use Walltite for an existing building, because of the more difficult installation method in comparison to beads. There is drilling involved that turns the walls in the same shape like a swiss cheese.

The horizontal spacing is more or less the same as beads (650mm vs 600mm) although the holes are smaller (12mm compared to 22mm with beads). The holes re small enough that drilling through the mortar joints is recommended, although that presumably requires a bit of skill.

It's the vertical spacing that differs, 450mm with foam compared to 2m-ish with beads.

So I guess there's about 4x as many holes.

As for the adhesion, the issue with all sticky things isn't the initial bond, it's the longevity that matters.

Wartburg

The difficulty I see is, that the Walltite will be bonded to two completely different materials. (Solid) block on the one side and (pretty weak) polystyrene on the other. Spraying it to a loose piece of polystyrene to check the potential reaction is not the same as have it applied in the cavity. You´ve probably heard or read that Walltite was causing structural damages to houses, because of wrong application.

Don´t think about carbon fibre for insulation purposes. Just block the cavity and use an external wall insulation. Easier and more efficient

caesarthechimp

Lumen wrote: »

The horizontal spacing is more or less the same as beads (650mm vs 600mm) although the holes are smaller (12mm compared to 22mm with beads). The holes re small enough that drilling through the mortar joints is recommended, although that presumably requires a bit of skill.

It's the vertical spacing that differs, 450mm with foam compared to 2m-ish with beads.

So I guess there's about 4x as many holes.

That's not far off the spacing for wall ties 900 wide and 450 (2x block courses) high.
There might be a problem with hitting the occasional tie if drilling into joints, but I agree a 12mm hole is so small it is not going to cause any damage to a wall.
I had the "pleasure" of being inside a house trying to talk to the owner while two lads drilled the larger holes outside. It was like continuous thunder, the whole house seemed to be shaking.

caesarthechimp

Wartburg wrote: »

The difficulty I see is, that the Walltite will be bonded to two completely different materials. (Solid) block on the one side and (pretty weak) polystyrene on the other.

Yes, if the foam is expected to replace corroded wall ties in any structural sense, then the cavity would have to be empty of any previous insulation. There are cavity walls from the 1970's like that (mostly brick faced)

Wartburg wrote: »

Spraying it to a loose piece of polystyrene to check the potential reaction is not the same as have it applied in the cavity. You´ve probably heard or read that Walltite was causing structural damages to houses, because of wrong application.

Well I think the chemical reaction will be over in the first minute, so either it reacts or it does not.
The structural damage is apparently due to expansion pressure, which is a different thing. I don't know much about how or why this happened, but i suspect if the manufacturers procedure had been followed fully, the problem might not have arisen.

A lot of the manufacturers of insulation systems run training courses and only supply their systems to their registered installers, because the manufacturer does not want to suffer reputational damage due to inappropriate/unlicenced use of their product.

Also you have to wonder, if a builder thinks the walltite will act to tie the walls together after it is pumped, would he think its ok to build the walls with fewer or no wall ties? Would the expansion of the setting foam then burst the outer leaf walls outwards?

Wartburg wrote: »

Don´t think about carbon fibre for insulation purposes. Just block the cavity and use an external wall insulation. Easier and more efficient

I meant that wall ties themselves could be made out of carbon fibre instead of steel.

Lumen

caesarthechimp wrote: »

Yes, if the foam is expected to replace corroded wall ties in any structural sense, then the cavity would have to be empty of any previous insulation.

This is an incredibly obvious point that Wartburg also made that hadn't occurred to me.

The expansion pressure thing is real - I've had chats with people (householders) In Ireland who advocate Walltite but who experienced cracked plaster and considered it a price worth paying. Now, maybe the installation was done wrong, but that doesn't reduce the risk unless the installer is willing to cover costs of any remediating plastering, which is doubtful.

So in the case of existing partial fill polystyrene (which I have), the fact that you're adding internal pressure to the wall without bonding to both inner faces seems indisputably bad.

Wartburg

Lumen wrote: »

This is an incredibly obvious point that Wartburg also made that hadn't occurred to me.

The expansion pressure thing is real - I've had chats with people (householders) In Ireland who advocate Walltite but who experienced cracked plaster and considered it a price worth paying. Now, maybe the installation was done wrong, but that doesn't reduce the risk unless the installer is willing to cover costs of any remediating plastering, which is doubtful.

So in the case of existing partial fill polystyrene (which I have), the fact that you're adding internal pressure to the wall without bonding to both inner faces seems indisputably bad.

I heard about a complete opposite reaction of a client of mine. The moment were he started talking about building damages (i.e. cracks in the wall) caused by Walltite, I was considering the expansion pressure as the reason too. But he told that it happened the opposite way - the chemical reaction of the two components of Walltite during the application is causing some heat and expansion but right after it can come to a contraction with a huge pulling force. Plastered walls do increase this effect, maybe because of being more air tight and affecting the chemical reaction in a certain way.

Wartburg

caesarthechimp wrote: »

I meant that wall ties themselves could be made out of carbon fibre instead of steel.

Won´t work because of the rough surroundings on a building site. The risk of damaging the carbon fibre during the block laying process is much higher than any benefit regarding long life span. I´d rather would think about a wall tie, made of a certain plastic material with all required properties. That would even bring a (slight better) value regarding thermal bridging in comparison to the common stainless steel version.

claimshandler

We have a house insulated with walltite BASF CAVITY FOAM , which is proven to be defective,has shrunk and caused very serious structural damage to the extent that the house is now uninsurable, and unmortgeable .

Looking to discover how other unfortunates dealt with this problem and what is the best solution!

https://www.boards.ie/discussion/comment/108567300#Comment_108567300

Lumen

https://www.boards.ie/discussion/comment/119848806#Comment_119848806

What's the cavity width?

larrymc123

https://www.boards.ie/discussion/comment/119849175#Comment_119849175

I am also interested to know what the cavity width was here.

I've been reviewing every discussion available on Boards.ie regarding the use of Walltite for cavity wall insulation, as I am seriously considering using it on retrofit/existing cavity wall (partially filled with existing 50mm polystrene).

Note I am still undecided as of yet. Major Pros are 1. Airtightness 2. Significantly minimises disruptive works internally (in comparison to fitting 62.5mm insulated plasterboard on internal walls). Major cons are risk of cracking/damage.

There has been reference to a few horror storys with Walltite install and I am wondering if were new builds, with a very large cavity (i.e. 300mm), and installed incorrectly (by someone who hadn't a clue what they were doing).

Evd-Burner

https://www.boards.ie/discussion/comment/120381808#Comment_120381808

So I went to go with waltite for the same reason as you. I reached out to BASF and got their approved supplier list, contacted a supplier. They did a check and said they wouldn't install waltite for me, it could cause more harm with moisture than good is what they said. Instead Enertite was installed 2.5 years ago and the difference has been unreal in the house.

larrymc123

https://www.boards.ie/discussion/comment/120382397#Comment_120382397

Thats interesting that the installer recommended against it. Can I ask what was your existing cavity build-up was?

With the Enertite, did you install this on walls internally and attic?

Evd-Burner

https://www.boards.ie/discussion/comment/120382868#Comment_120382868

So the cavity was 100mm with 50mm polystyrene in place, although from inspection it seems it was loose in places. This cavity was filled from the outside.

I also had a 35m-50mm cavity behind the internal blobbed wall which was filled internally.

I was told that the mix was a slow curing mix so that it gets in everywhere as such. I could hear all sorts of snaps and pops as it was curing in between fills, assuming some of that was the existing insulation being pushed back into place.

larrymc123

https://www.boards.ie/discussion/comment/120383068#Comment_120383068

Oh, thats a new one on me! I knew Enertite was used internally in Attics and on internal wall side, but I hadn't heard of anyone pumping it into external cavity wall.

Lumen

https://www.boards.ie/discussion/comment/120383247#Comment_120383247

That application is not listed on the website and I suspect it's not certified for that either.

https://enertite.ie/spray-foam-insulation-applications/

Evd-Burner

Sorry busy 2 days.

It was a very reputable company that were an approved supplier from BASF, a lot of what they specialize in was correctly badly installed insulation. It could be that I am mixing up that Enertite went into the cavity wall and instead it only went into the blobbed wall cavity with something different going into the cavity wall as it is white/yellowish and not purple

They were explicit in that they could not use waltite for my house. Since install I haven't had any issues and the difference in heating an air escaping has been very noticeable.

Lumen

https://www.boards.ie/discussion/comment/120390976#Comment_120390976

I can find only one BASF product with an NSAI cert and that's:

CERTIFICATE NUMBER: 18/0403

ENERTITE OS 200

Manufacturer: BASF PLC

Product Area: Thermal Insulation

You can search yourself here

https://www.nsai.ie/certification/agrement-certification/search-agrements-certificates/

That cert does not include use in a double leaf masonry cavity. Is that what you have, or do you have a single skin masonry with a timber frame internally? If the latter, I don't see how it could have been installed from the outside.

From what you've posted it seems like you have had an uncertified product installed.

IAB180403_ENERTITE_2020.pdf

halosecurity.ie

We are currently deep-retrofitting a two-storey house which was originally completed in 2004.

The walls are mainly rendered block cavity wall but with brick to the ground floor on the front elevation. There is EPS in the cavity to 50mm

I am seriously considering CV100 for the cavity and then would render the front elevation to hide the brickwork which we don’t find aesthetically pleasing.

The walls are in good condition.

The property is around 6000Sq. Ft and draughty but we’re working our way through it with extensive use of tapes, membranes, downlighter covers etc.

We are replacing all doors and glazing with 0.7u performance.

All attic hatches are air-tight

All passive vents are being closed and ventilation will instead be done via MVHR -specifically 2x ProAir 750Li units.

We removed all the old insulation from the attics and hoovered it out. We’re fitting 20 Glidevale G5 vents to ensure the attic is cold and well ventilated.

Insulation plan:

Attic:

Enertite to 50mm on attic floor joists to ensure good air-tightness to ceiling throughout (it was impractical to apply membrane to existing ceilings)

Enertite to between 150 & 200mm on back of rising stud of converted attic from attic floor to rafter (to seal joists running under converted attic)

Enertite to 2x Velux tunnels

400mm of blown insulation to floor of attic

Walls:

CV100 ticks all the boxes to get the wall airtight.

Econ-PU, the distributors, say:

Our walls are ideal as the limited space (50mm) means there will simply not be enough space to fit sufficient CV100 to deliver enough energy to damage the walls.

TIn worst case, the existing EPS will absorb any excess pressure by compressing

The EPS will perform better as it will be pressed tight to the wall by the CV100.

Question:

Some folk have mentioned that the contraction of CV100 could cause the inner and outer leaves to be pulled inwards in the case of a full cavity fill.

Does the partial EPS fill not eliminate that risk as the CV100 will only be bonded to one wall leaf & the EPS?

To be honest, CV100 is the perfect solution in my opinion, if installed by someone competent.

If I can mitigate the major risks, I’d be inclined to go with it?

All input greatly appreciated? 🙏

Lumen

That's an interesting point.

However, from the cert

This Agrément Certificate Product Sheet (1) relates to BASF Walltite CV 100 Cavity Wall Stabilisation System, a rigid polyurethane foam injected in liquid form, to stabilise external masonry cavity walls in which conventional wall ties have corroded. The product stabilises the wall by adhering to the inner surfaces of the cavity and providing a continuous structural connection between the two leaves

Obviously you're relying on it not being able to do this specific job.

The other risk I recall being discussed is degradation of the wall ties by trapped moisture.

In the certified application the ties are already degraded but there's adhesion to both leaves.

The worst case is that your wall ties degrade and cannot be rectified by application of more Walltite, in which case a conventional approach (e.g. new wall ties bolted through the double leaf) would be needed.

The general issue that the product is not certified for the application you're using it for (unless there's some other cert that's been done since I started this thread).

The conventional alternative is bonded beads even though 50mm isn't a lot of space to fill and I imagine there might be voids.

Would like to hear how you proceed because I still haven't sorted mine out.

10-10-20

I'm in the same boat, house is a 2003 cavity build with 50mm PIR boards. I also have the red brick to the ground floor on the front elevation, but I'm not planning on rendering mine. I'll have to possibly look at bonded beads for that bricked section and CV100 for the remainder of the house.

Regarding the wall ties, do we know if the "conventional wall ties" referred to above relate to the modern stainless steel type or could it be an historical reference to the older early 80's and older types which were not galvanised, etc?

Lumen

https://www.boards.ie/discussion/comment/121289177#Comment_121289177

Stainless or composite wall ties won't corrode, so it must be a reference to the "old" ones. My house is an '87 built so presumably they're regular steel.