Sovereign Hey’di K11 really needed?

[NWGEAR]

The scenario is a barn conversion with 50cm thick stone walls. Internal structural timber frame is specified demoting the stone walls to a facade rain shield. The architect notes specify application of

Sovereign Hey’di K11 to the internal stone surface to mitigate damp issues. The builder "ain't seen this before" and doubts the effectiveness given the timber frame has the usual comprehensive DPM and vapour barrier 50mm stand-off from the stone walls. The 50mm cavity is to be ventilated. I support the builder's pragmatic view, but I'd like something on the stone wall, not least to prevent debris falling into the cavity off the stone wall (natural stone with lime pointing). The question for you lot is whether to go ahead with the K11 tanking or don't bother. The builder showed a couple of other jobs drawings where it's not specified. Perhaps a case of belts and braces from the architect.

 

An aside is the following pic, finally getting started on the build, floor dug and prepared waiting on steel mesh and sub-floor. ? (builder also reckons mesh is overkill +£500)

 

[PeterW]

I like your builder. 
 

Mesh in solid floors especially where they are on solid bases is pointless until you get over around 30sqm and even then adding fibres is simpler and cheaper. 
 

Architect has specced a pointless product too - I assume you’ve read the BBA Cert..??

 

Sovereign Hey’di K11 is a salt resistant cementitious tanking compound for the protection of structures against water from the ground and which maybe potentially subject to hydrostatic pressure.

 

So basically it’s only designed to protect from ground water ie below ground installs, and you’ll probably create more problems than you solve. 

 

[simon45089]

I have now converted 4 barns at the same site, as well as reformed the original farmhouse. I used K11 on all of the properties and I am a fan. None of the buildings had a damp proof course, so Heydi K11 to a metre and a half from the floor stopped any rising damp.(Good to have the guarantee for resale, and you can  register  yourself  as an installer so you can issue the certificate if you are so inclined). I have some west facing elevations which are seriously exposed to the Northumbrian weather, and powerfully wind driven rain on occasion. One year after a storm the rain came through into the farmhouse right through the 500mm walls.  (This wall had no stud wall on the internal face so I could see what was going on) There was a distinct line showing the penetration was all above the tanking and that the K11 had prevented all penetrating damp. As a result I tanked the wall full height. In the whole scheme of things its not that expensive a product and is defiantly a DIY job if you strictly follow the instructions.

When I first used it 15 years ago following recommendation from a surveyor, the rep told me to do it myself as it was not difficult. He had just sold a batch to a lady who was using it on the inside of her swimming pool !  It works.

 

[NWGEAR]

Thanks both for the reply. I see there are other products to choose from and I'll probably do something in order to stabilise debris, bridging would be bad. Definitely not dealing with hydrostatic pressure here so K11 seems overkill. Let it breathe they all say, let it breathe!

[Garry MCIOB]

Hi Just joined this thread due to looking for something else. When I look at your pic and how old the place is then read an architect has specified K11 then someone else  using it on other farm buildings that will now be ruined, I despair. In a nutshell I am a chartered builder and work in conservation carrying out historic survey and consultancy advice. Ben recorded a podcast a short while ago and explains everything about what you have and how it will work without any K11 or anything else that is sold by chemical companies. Please have a listen then make you mind up. Thanks 

https://www.buildingsustainabilitypodcast.com/guests/ben-kerslake/

[NWGEAR]

Hi Garry, don't despair, at least not in my case. I've been quite red-pilled on the use of natural lime breathable solutions rather than destructive techniques. I'm surprised by the architiect since he was aware of my preference towards a breathable solution, and is an advocate of it. Like I said, K11 is even more unneccessary since this has an internal timber frame decoupled from any potential damp issue. I was disappointed with the requirement to have the timber frame, since the existing walls are in excellent condition and I hoped the new roof structure could bear on existing walls. Alas the structural engineer insists on the timber frame, and I can empathise with his perspective dealing with known structural elements. The project loses in terms of missing a beautiful stone interior and also 100mm floor space on each wall. Besides structural reason, the building control requires the high insulation of the timber frame. Ho-hum. Next project will be "repairs" under the radar. Thanks for podcast link.