Recently reported issues with wood fibre board IWI

[Lacan07]

Hi all

I recently stumbled upon this post on a FB group I follow so I thought I'd share it here.

I realise this subject coincides with RenoAI recent post but I was planning to start this thread last week. I'm currently prepping my walls for wood fibre IWI so it seems it might be time to do some serious digging amongst the suppliers and manufacturers.

Unfortunately I've been unable to find the original FB post on Brad O'leary's page (deleted possibly?) as its useful to read the comments that followed. I hope he doesn't mind me sharing it on this platform.

Its seems to me there could be myriad of reasons for failure including permanently wet walls. One has to assume the manufacturers have performed some kind of long term testing, many state the product is not intended for wet walls. I'm not convinced it could be due to condensation, with 40 - 60mm board the dew point would surely occur much further back within the colder recesses of the wall. I'd been told on another platform by someone who used to work for a manufacturer (Steico I believe) that testing for condensation had been very comprehensive and it wasn't an issue provided the rules on thickness were observed.

I had always wondered about the stipulation of branded NHL lime however bearing in mind its reputation. My plan was to use non-hydrated lime as the base and the final skim on to the board. These branded NHL products are expensive and most manufacturers never used to insist on using it as a bond between the boards and the base until very recently.

 

[jsmac]

I am going to watch this discussion with interest. I too am (was?) planning on incorporating some IWI on a single skin external brick wall but have had reservations and questions about how best to go about it.

 

[fernicarry]

In what way has it failed? WF comes apart very easily anyway so once its been bonded to the wall its never going to come back off in one piece.

The gap in the second picture looks the same size and shape as an electrical back box. Those will always tend to be cold spots and could encourage condensation.

 

[a twig]

Would somewhat agree, those photos don’t actually seem to show any of the failures they have led to it being yanked off the wall…

 

[LadyArowana]

The gap in the second picture looks the same size and shape as an electrical back box. Those will always tend to be cold spots and could encourage condensation.

Could it be that they were chasing out for the installation of the socket and cable and discovered things in poor condition behind?

 

[Lacan07]

In what way has it failed? WF comes apart very easily anyway so once its been bonded to the wall its never going to come back off in one piece.

The gap in the second picture looks the same size and shape as an electrical back box. Those will always tend to be cold spots and could encourage condensation.

Yes, it looks quite dry doesn't it. And thats definitely a back box enclosure.

Its rather frustrating when people post stuff like this without any real context.

 

[Lacan07]

Could it be that they were chasing out for the installation of the socket and cable and discovered things in poor condition behind?

I'm not sure, I think he's just a lime plasterer

 

[Mulder]

Is Brad suggesting that the WF boards, with their low density, allow easy moisture movement until it hits the more dense brick/plaster behind, at which point it kind of backs up? Like a dam in a stream? Creating an area of increased moisture at this barrier that takes much longer to dissipate and could, over time, degrade the WF boards?

An interesting thought if so.
But presumably this is only a problem if the permeability is such that it can't keep up with the amount of moisture generated, which would surely be the case pre-WF boards too? Although surface evaporation may have made it less concerning.

 

[Kearn]

Is Brad suggesting that the WF boards, with their low density, allow easy moisture movement until it hits the more dense brick/plaster behind, at which point it kind of backs up? Like a dam in a stream? Creating an area of increased moisture at this barrier that takes much longer to dissipate and could, over time, degrade the WF boards?

An interesting thought if so.
But presumably this is only a problem if the permeability is such that it can't keep up with the amount of moisture generated, which would surely be the case pre-WF boards too? Although surface evaporation may have made it less concerning.

The transport of moisture is the other direction I believe, through the wall out to in, but can no longer evaporate due to the boards.

 

[Itchinfilth]

The transport of moisture is the other direction I believe, through the wall out to in, but can no longer evaporate due to the boards.

I think that's what the message was. Restores and works on a lot of period stone properties up in the lake district.

 

[fernicarry]

Would be useful to know what the external condition of those buildings was. If the wall is saturated then you can expect a certain amount of evaporation from the internal face but you really want that to be the exception and short lived otherwise your living spaces will always have high humidity. Maybe some buildings are just like that due to their exposure so aren't suitable for that sort of treatment.

To what extent is WF hygroscopic? The hemp stuff I use can at times feel damp to the touch when I'm installing it. Its quite spooky because everything around it is bone dry and you think to yourself how did that get wet? Presumably once its in the wall it will be doing the same thing, sometimes full of buffered moisture, other times not. Digging into it and finding it feels wet doesn't necessarily imply its always wet if that's what he means by failing.

 

[Kearn]

I think that's what the message was. Restores and works on a lot of period stone properties up in the lake district.

Yeah, I’m aware of Brad. I inadvertently sparked a bit of argument about this post in one of the precious lime plastering forums…!

 

[Kearn]

Would be useful to know what the external condition of those buildings was. If the wall is saturated then you can expect a certain amount of evaporation from the internal face but you really want that to be the exception and short lived otherwise your living spaces will always have high humidity. Maybe some buildings are just like that due to their exposure so aren't suitable for that sort of treatment.

To what extent is WF hygroscopic? The hemp stuff I use can at times feel damp to the touch when I'm installing it. Its quite spooky because everything around it is bone dry and you think to yourself how did that get wet? Presumably once its in the wall it will be doing the same thing, sometimes full of buffered moisture, other times not. Digging into it and finding it feels wet doesn't necessarily imply its always wet if that's what he means by failing.

The boards aren’t wildly hydroscopic I don’t think, some even have an external facing water resistant coating, so clearly not. Think they are all bound with something that holds its structure dry, but not so great when it gets wet. Not as bad as the wood wool boards though!

Wood fibre insulation batts on the other hand are brilliant at getting soaked and then fully drying out quite quickly.

 

[Brad Oleary LDPR]

Hi all

I recently stumbled upon this post on a FB group I follow so I thought I'd share it here.

I realise this subject coincides with RenoAI recent post but I was planning to start this thread last week. I'm currently prepping my walls for wood fibre IWI so it seems it might be time to do some serious digging amongst the suppliers and manufacturers.

Unfortunately I've been unable to find the original FB post on Brad O'leary's page (deleted possibly?) as its useful to read the comments that followed. I hope he doesn't mind me sharing it on this platform.

Its seems to me there could be myriad of reasons for failure including permanently wet walls. One has to assume the manufacturers have performed some kind of long term testing, many state the product is not intended for wet walls. I'm not convinced it could be due to condensation, with 40 - 60mm board the dew point would surely occur much further back within the colder recesses of the wall. I'd been told on another platform by someone who used to work for a manufacturer (Steico I believe) that testing for condensation had been very comprehensive and it wasn't an issue provided the rules on thickness were observed.

I had always wondered about the stipulation of branded NHL lime however bearing in mind its reputation. My plan was to use non-hydrated lime as the base and the final skim on to the board. These branded NHL products are expensive and most manufacturers never used to insist on using it as a bond between the boards and the base until very recently.



View attachment 18969

What would you like to know?

 

[stuart45]

What would you like to know?

How did you know you on here?

 

[Brad Oleary LDPR]

In what way has it failed? WF comes apart very easily anyway so once its been bonded to the wall its never going to come back off in one piece.

The gap in the second picture looks the same size and shape as an electrical back box. Those will always tend to be cold spots and could

 

[Brad Oleary LDPR]

So in a nutshell!
The wf boards, the diathonite and the adhesive were not moving moisture as efficiently as the traditional lime mortar externally. So the wf board was hanging wet.
When I chased out for a socket I found high levels of moisture, I mean it was wet to touch.
There had been a wet period followed by a prolonged dry period.
I was not the original contractor who installed the system.
I do not agree with iwi on traditional solid walls.

Any questions?

 

[a twig]

So doesn’t this come back to “you shouldn’t insulate until you have sorted out the wall and made sure it’s dry in the first place?”

Personally I’ve never used adhesive or diathonite so maybe that’s a factor?