Advice on an 1880's Victorian farmer cottage

[Matthew309]

I have recently purchased an 1880's Victorian cottage ( it used to be two semi's). The whole house is in need of serious renovation, so we have got temporary housing and I'm stripping the house to a bare shell.

Main points to consider :

1. Structural movement:
   • The house has only about 3 or 4 courses below ground level before hitting a light rubble mixture mixed with clay. The downspout flooded a few years back and caused the corner of the house to drop. I'm monitoring the cracks currently and waiting to decide if underpinning this corner is the right course of action, especially given its age.
   • Dodgy window fitters installed the windows without lintels so the brickwork above the windows will need removing and repointing.
   • the bricks below ground level have completely companied lime mortar. Its filled with mud and roots, is this something that worth repointing even if its below ground level. (I noticed because we dug down to expose the footings for a patio and lower external ground level.
   • the whole house has been repointed with rock hard cement, causing brick to spall.
   • the floor level inside the house is slanted in various areas
2. Damp
   • The entire house is lined with a Bitumen Newton light lath and plaster on the walls that has made all the plaster pop internally and therefore sounds hollow; this extends up the the eaves.
   • There is no DPC,
   • the screed internally has a dpm beneath it, where this meets the base of the wall it appears to be damp.
   • there is also damp on the internal chimneys central to the house. I was thinking leaving them all exposed to help any moisture evaporate in the house and keep them dry with the log burner.

My plan of action for repairs (in order)

• Monitor movement on the corner, if the crack opens by more than 5-10mm than it already has - Underpin it
• Strip the whole house back to a bare shell
• Lower exterior ground level.
  • This is an issue because lowering the ground level to below internal level basically bring you to the last brick at the base of the foundation.
• Repoint ground floor bricks with lime, then coat with masonry breathable repellent to prevent water ingress. Then eventually repoint upstairs too.
• Either insert a physical DPC or injection
  • This im not sure about because if the DPM on the flooring has already been installed, and is pushing damp to the wall, the only way to prevent it entirely is to continue that physical barrier through the wall via a physical DPC
• build an internal cavity wall from CLS and DPM it with celotex insulation, but not making it too thick as to still provide warming of the walls through heating the house.

Any advice and guidance on a project like this is much appreciated.

Thankyou in advance.

 

[malcolm]

There are a lot of questions there and no photos so we can't see the stuff you think is not important enough to mention. For me I've had a lot of success letting a brick building dry to the outside after removing all the waterproof mortar/coatings. Don't try to keep the water out from outside. Let the water get out from the wall and don't use waterproof coatings.

I've not bothered with damp proof courses as they aren't needed if water can evaporate away once it gets into the wall especially if it has a brick or two to evaporate before it gets to internal ground level. I do have a wall that might benefit from underpinning but insurance companies always ask if the house has ever been underpinned so it's cheaper to let the lime mortar be flexible and accommodate the movement.

Stripping a whole house is quite a big job. I've left a lot of concrete plaster inside mine. Soaking wet walls do need somewhere to dry and drying to the outside is more effective and less disruptive.

 

[aockenden]

I would definitely rethink your dry lining plan (CLS battens + celotex). Many have tried, most have asthma. If you’re dead-set on that approach, getting lots of thorough ventilation between the celotex and the cold masonry behind will be of absolutely paramount importance. There are a number of different approaches for doing so, most of which are fraught with challenges. A brick house makes it more likely to succeed though, so you’ve got that going for you.

 

[Matthew309]

There are a lot of questions there and no photos so we can't see the stuff you think is not important enough to mention. For me I've had a lot of success letting a brick building dry to the outside after removing all the waterproof mortar/coatings. Don't try to keep the water out from outside. Let the water get out from the wall and don't use waterproof coatings.

I've not bothered with damp proof courses as they aren't needed if water can evaporate away once it gets into the wall especially if it has a brick or two to evaporate before it gets to internal ground level. I do have a wall that might benefit from underpinning but insurance companies always ask if the house has ever been underpinned so it's cheaper to let the lime mortar be flexible and accommodate the movement.

Stripping a whole house is quite a big job. I've left a lot of concrete plaster inside mine. Soaking wet walls do need somewhere to dry and drying to the outside is more effective and less disruptive.

I couldn't access my photos at the time, here are some images of the house

 

[Matthew309]

I would definitely rethink your dry lining plan (CLS battens + celotex). Many have tried, most have asthma. If you’re dead-set on that approach, getting lots of thorough ventilation between the celotex and the cold masonry behind will be of absolutely paramount importance. There are a number of different approaches for doing so, most of which are fraught with challenges. A brick house makes it more likely to succeed though, so you’ve got that going for you.

What's the alternative with this type of wall construction and lack of DPC? I was going to use mineral wool or fibreglass with a vapor barrier system to prevent rot. The below diagram is the design i was thinking:

 

[aockenden]

What's the alternative with this type of wall construction and lack of DPC? I was going to use mineral wool or fibreglass with a vapor barrier system to prevent rot. The below diagram is the design i was thinking: View attachment 14738

With the wall vents you’ve drawn in, you might get away with it.

The alternative is to use natural breathable materials throughout. Given that you have flat (ish) brick walls (instead of stone) there are more and easier options available to you. These other options will prevent the trapping of damp (rising, penetrating and condensation) between layers of modern impervious materials.

The approaches typically involve breathable plant-fibre based boards (wood-wool, wood-fiber and sometimes cork) being generously coated on the backside of the board with clay or lime, then being “mushed” directly onto the cold bare brick wall, and then fixed mechanically with thermally broken fixings through the board and into the cold brick behind. Lastly the front surfaces are plastered with clay or lime plasters and finished with clay or lime paints.

These systems create a continuous capillary network through all the layers of the wall which is able to pull condensation forward and evaporate it back off into the room.

There are also insulated lime and clay plasters (where sand aggregate has been replaced with some kind of insulating aggregate such as hemp, granulated cork, perlite, pumice, charcoal, etc.) which can be directly applied onto cold masonry walls to improve their thermal performance and manage moisture. These are typically less insulating per unit of thickness vs the breathable boards discussed above and are typically used in situations where you have lumpy / curvy stone walls and want to maintain that aspect, so flat boards won’t work.

Honestly, the fact that you had to ask about alternatives to your above approach indicates that you have significantly more research to do before committing to an approach.

 

[jamest]

That proposal shown in the diagram is not going to offer much insulation given the total added depth you've specified (between about 7.5 cm and 10 cm) and the thickness of plasterboard + vapour control layers (about 1.5 cm plus plaster skim) plus the gap (3 cm). Your insulation layer is then only between about 3 and 5 cm, plus you've in effect lost some of the thermal mass and thermal resistance of the solid wall by inserting vents in it. In the worst case that's hardly more insulating than an unvented 9 inch solid wall with standard plaster. If it were me, I would be abandoning that approach as offering nothing much in the way of insulation and going with one of the breathable board systems mentioned by aockenden. That way you retain the thermal mass and modest resistance of the solid wall and that of the insulation itself (wood fibre and cork have significant thermal mass, whereas PIR and rockwool do not). With lime plaster, you also get a wall that manages moisture and won't get mould on it (or behind it) or anything nasty like that. I've used both cork and wood fibre board in my house and they really are a doddle to DIY, much easier (in my opinion anyway), than building a studwork frame, fitting vapour bariers and trying (and usually failing) to get everything perfectly airtight.

 

[a twig]

Lists of useful information in this thread covering both wood wool and wood fibre insulation options and installation methods - in your case I’d just apply wood fibre direct to the walls and plaster over it