The beginning of the solid wall insulation retrofit journey…

Traditional methods such as lime plastering are often the preserve of buildings deemed to be of historical importance, yet it seems to have been forgotten that more modest properties such as the ubiquitous victorian terrace were also built with solid walls, lime plaster and a need to ‘breathe’. The designers and craftsmen who built them, were creating a carefully balanced internal climate to ensure occupant comfort, avoidance of damp & protection of the fabric of the building and its structural integrity.

Lime plastering and more conservation approaches to damp remediation remain a niche area with the skills required attracting a cost premium. Rather than increased material cost, this may be more to do with skills being lost during two world wars, followed by a product-led approach to construction. It should be noted that the need for expensive injected ‘damp-proofing’ & tanking treatments are often ill-advised and ineffective, with the actual causes often easily and cheaply remedied.


Upon peeling away the layers in the front room of my small victorian terraced house, I was able to begin to piece together the jigsaw that paints a picture of a history of damp problems and attempted remediation.


The front bay and the corners of the room were damp with peeling paper. Underneath we found gypsum, cement render in places and a tide mark of salts creating a crumbling, bulging mess where the more modern gypsum met the old lime. The moisture was clearly trapped behind the gypsum & had simply migrated up the wall, escaping when it found the permeable junction where the lime plaster allowed it through. This small border of lime plaster, unable to cope with such high levels of moisture and salts, has ‘exploded’ or blown under the pressure!

This attempt to ‘tank’ with cement & gypsum to ‘hold back the damp’, had only succeeded in trapping moisture & damaging the bricks underneath. The continuing issue of excess moisture in the house and condensation on the cold surfaces has not been properly addressed. Other potential contributing factors previously unidentified and unaddressed are the high ground levels outside along with leaky guttering and poor roof maintenance.

The floor is in poor condition with repeated attempts to replace the rotten, woodworm infested floorboards only resulting in more of the same results due to the real causes not properly being dealt with. I am excited to begin unpicking the why’s and how’s of these issues, hopefully halting the cycle of damage. In doing so I hope to restore the building to health and pass on what I have learned to others.

After much research, I decided that hempcrete might be the perfect solution to help insulate and draft-proof whilst retaining the required vapour-permeability of the lime-mortared brick walls. As I understood it, this method could act as a ‘buffer’ for excess moisture vapour to reduce condensation issues whilst improving comfort and air quality.

I found a workshop hosted by Neighbourhood Construction in Bristol, which utilised kinaesthetic peer-to-peer teaching to learn about how old buildings behave & the installation of a hemp-lime bio-aggregate (a.k.a hempcrete) to the original solid walls.

This was a fascinating experience and a wonderful opportunity to meet like-minded people. We were introduced to the idea of ‘internal weather’ which enabled us to expand our understanding of how occupant behaviour and habit adjustment can affect damp issues. Additionally we explored the logistics of installing hempcrete as a retrofit, creating systems and methodologies on site that everyone can understand and benefit from.

After attending the workshop and obtaining some further consultation from Neighbourhood Construction; I felt more confident to plan and execute an installation in my own home. I will be hosting a workshop to pass on this knowledge and offer hands-on experience to other practitioners. Self-installation will reduce labour cost whilst providing an empowering experience, an opportunity to connect with the house and make it my own, whilst learning skills that will enable later alterations or repairs if needed.




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