How to turn a lovley old house with solid walls into a warm efficient home




Once I had all the boards tightly fitted to the walls, ensuring no gaps around the insulation where it met and allowed access for backboxes etc. I was ready to plaster the boards. In order to meet my vapour open spec I planned to use a lime based plaster. However, I had to ensure it was appropriate to work with the magnesium silicate board. Much is talked about 'lime' in the old building business, but I also happen to think that a lot of nonsense it talked and the best products are often not used. I located a product called Fibrelime. The owner of the business, Joe Orsi, was well knowledged about lime and also new products such as silicate boards. Joe had developed a primer to work with the silicate boards and a lime product containing fibres to work specifically for my sitaution. Being fairly new, Joe agreed to come along to show me how to use the products and we began the plastering together.

Fibrelime, render, lime, eco, home, renovation

The magnesium silicate boards appear quite smooth, so the  primer was crucial to the keying of the lime plaster. Joe had developed the primer for use on these boards but remaining vapour open. It contained a grit in the mix. Once the joints were scrimmed we painted the primer liberally onto all the boards and gave it 24 hours to dry.[/col]

[col class="span3"]Fibrelime, plastering, lime, eco, breathable[/col]

[col class="span4"]Fibrelime is a mix of lime, chalk and super fine fibres (plus secret ingredient). It was important to keep the mix as dry as possible as too much water will increase the likelhood of cracking. However, too thick and it's really hard to trowel, so it's a comproomise. The mix is silky smooth and easy to work with.Fibrelime[/col]

[col class="span4"]Fibrelime, putty, [/col]

[row id="ROW_ID" class="ROW_CLASS"]
[col class="span3"]Fibrelime, plaster, eco, green deal, home[/col]
[col class="span6"]To mix the plaster you have to use an openended mixer becasue the fibres bind around a normal mixer and clog it up. Other than that you mix it as you would with gypsum - it's just thicker. I re-rendered the internal walls of the same rooms and continued the fibrelime throughout so that it would all match. As part of my WUFI modelling I even specified the paint as modern paints can be very vapour tight. I didn't want to ruin my attempts to remain vapour open so I used Keim paints. They are a German paint company that produce very matt paints suitable for an old house but they specify they vapour permeabilty of their paints, something few companies do.[/col]

[col class="span3"]Lime plastering, fibrelime, eco, green, breathable[/col]

[row id="ROW_ID" class="ROW_CLASS"]
[col class="span4"]Messy job but I was very happy with the result. It is very hard for me to quantify the effect of the insulation. Anecdotally, I can say that the house and rooms feel warmer and are easier to heat and less draughty. I do realise that I have done a considerable amount to the house, however, so it's not always easy to say what efforts have provided the greatest improvements.

A couple of years on and I can say the room still looks great. I am not aware of any damp issues, cracks or problems of any sort.[col class="span4"]

Lime plastering, wufi, breathable[/col]


© Christopher Thompson