Hello, from Maastricht

[Aisha]

Hello builders,

My name is Aisha. I live in Maastricht, the Netherlands. I’m renovating mij 250 years old marlstone barnconversion and for that reason, I’m interested in what you guys do to improve your old limestone or sandstone building. How you deal with moist coming from the walls, lime plaster, ecofriendly ways to insulate, floor heating and the like. I do have some experience with it, so if I can shed a light, I will be happy to do so. If you have experience with cork insulation on damp walls, I will be happy to learn from you. ( the moist transport itself through the walls is not to be solved, it’s the nature of marlstone to stay slightly moist)
Best regards, Aisha

[Redbeard]

Welcome.

 

I'd suggest dense, breathable insulants such as rigid wood-fibre or cork. You/we will need to try to build up a 'picture' of the 'slightly moist' nature of the marl. Breathable insulants can be a help to breathable walls. They are not an instant solution to wet walls. If this is a conversion, how are the internals finished? Plaster? If so, gypsum or lime? Plasterboard? Is it insulated or not?

[Aisha]

Hi,

thank you for your kind reply. A bit more about this house and what I did to it so far:

it is converted into a house in the 80’s. It used to be a barn. Before that, it was a farmhouse. It’s more than 250 years old. When we bought it, the walls were covered with portland cement on the outside and with paster with gypsum on the inside. We live here since 2012 and are renovating it bit by bit. I have asked a marl specialist company to help with the damp issues in this house. As you see on the photo, the outside of the walls is beautifully restored by them.  The roof is insulated with cellulose paper, the ceilings/ attick floor idem.It has balanced ‘warmth winning back’ ventilation system to solve the issues with damp. The air in the house is about 50/55% moist now, much better than the 80/90% it used to be. Plaster is removed from the walls. The floor in the room I’m working at , 17 m2, you can see on the photo that the floor inside is about 50 cm higher than the ground outside. The floor is digged out 40 cm, insulated with blast glass agregate , the next project is to create a breathing ‘limecrete floor’ on top of that with underfloor heating pipes. So I guess I did all the good work so far.
There is nothing that stops the moist transport from the underground into the walls, it’s the nature of marl. Same with the inner marlstone walls. If you stop it, the marl dries out and the stones will detoriate. So we have to deal with it and take good care of the walls. I worked on this room before, taking the gypsum plaster off and replaced it with a thick layer of clay mortar/loam. Unfortunately that plaster stays too moist and has started to mould. I have stripped the walls again and this time I added the glass blast floor insulation, hoping it will also help the walls to ‘breathe’. This time I have experimented with a selfmade insulating lime mortar to get the walls flat/less ondulating. The recipe is as follows: 12 parts perlite, 12 parts expanded cork granules, 8 parts nhl 2 lime, 4 parts hydrated lime, 2 parts diatomite earth, a bit of fibers. Nice, light, airy stuff to work with, not heavy like lime with sand.

To get this layer of lime really insulating I should make it at least 6 cm thickness. That is a lot of work, with the risk that it will start to mould again… so, now expanded cork plate wall insulation comes to my mind. Will it take away the sense of radiating cold?  Do you have experience with it?

Hope to learn from you soon,

best regards, Aisha

 

[Mike]

You have an interesting building and some interesting challenges there!

 

For the walls, consider lime-hemp (hempcrete), which can be applied directly to the wall in multiple layers, or cast against it using formwork. There are multiple examples of both on the internet, at least in French. Hemp handles moisture vapour very well, though not liquid liquid water, so you would need to make an assessment on the suitability and thickness. Your self-made insulating lime mortar sounds an interesting alternative.

 

If you have lots of damp below the floor, you might want to consider laying ventilation pipes within the glass aggregate, connected to an extractor fan. If you search for hérisson ventilé you will find some examples. This may be enough to make the walls suitable for the hempcrete, if you think that it may be otherwise too damp.

 

If the walls are still too damp for hemp, then your idea of expanded cork sheets sounds good, since cork won't be affected by moisture. I've used it myself in small areas - mainly on my chimney breasts - fixed with lime-based Isovit e-cork.

 

You haven't mentioned how you are ventilating the building. I would suggesting using some form of continuous mechanical ventilation - dMEV / MEV / MVHR - to help control the internal relative humidity.