Ground floor concrete slab installation

[fullern]

Hello,

So I am in the midst of what has now turned into a renovation project of a cornish cottage and am looking at doing up the lounge area.

We are planning on taking off all the internal concrete render and plaster from the walls, re pointing everything in lime mortar and then re plastering and using some form of breathable insulation (eg cork) to try and stop the terrible damp problem we have.

Prior to this though we need to tackle the floor. There is currently a wooden laminate esque floor in situ which has warped due to damp, and in some places gone black with mould. It is approximately 8m squared in size.

What I want to do is rip out the flooring, dig down then put in a concrete slab, with insulation on top and then whatever form of flooring we choose (swithering between carpet or UFH with wood flooring).

So my questions are;

As the property needs to 'breathe' is there any point in putting down a damp proof membrane, considering there is now way of incorporating it into the walls (if that makes sense) at the edges.

Has anyone had any experience with 'limecrete'? Whilst I am wanting to maintain the breathability of the property, would a concrete slab be problematic? My understanding would be that any moisture would simply be driven to the walls, which themselves will be breathable, and so it can escape.


Does this sort of a project need to be cleared by building standards?

I realise there will be a lot of work but I am seeking to do this myself with the help of some friends who are involved in various building trades.

Any guidance or suggestions would be very much appreciated, I am just at the initial planning stage at the moment and trying to gauge potential difficulties. Oh and I am out of the country for a few months so can't post any photos or anything sorry!

Many thanks to anyone who replies,

Regards
N.

 

[RNReindeer]

Hello,

So I am in the midst of what has now turned into a renovation project of a cornish cottage and am looking at doing up the lounge area.

We are planning on taking off all the internal concrete render and plaster from the walls, re pointing everything in lime mortar and then re plastering and using some form of breathable insulation (eg cork) to try and stop the terrible damp problem we have.

You need to consider proper dry-lining, or use lime plaster and maintain the breathability of the walls.

Most properties, if left uninhabited for a period of time will suffer from condensation, and therefore mould.
The key, in uninhabited properties is ventilation, ventilation and ventilation.

Prior to this though we need to tackle the floor. There is currently a wooden laminate esque floor in situ which has warped due to damp, and in some places gone black with mould. It is approximately 8m squared in size.

What I want to do is rip out the flooring, dig down then put in a concrete slab, with insulation on top and then whatever form of flooring we choose (swithering between carpet or UFH with wood flooring).

So my questions are;

As the property needs to 'breathe' is there any point in putting down a damp proof membrane, considering there is now way of incorporating it into the walls (if that makes sense) at the edges.

Has anyone had any experience with 'limecrete'? Whilst I am wanting to maintain the breathability of the property, would a concrete slab be problematic? My understanding would be that any moisture would simply be driven to the walls, which themselves will be breathable, and so it can escape.

Absolutely yes include a dpm in the floor.
The floor tends to only breath in one direction - upwards. There is no breathability into the floor.
Depending on the thickness of the walls and whether you are intending using the walls and floor as a heat-sink, conside placing the insulation below the concrete.
Sorry, no experience with limecrete.
I suspect that purchase, delivery, etc of normal concrete will be much less problematic, and with a dpm in the floor there is no advantage, other than ecological considerations.
You can turn the dpm up at the edges and trap it between a non-de-compostible material sch as PVc or ceramic for the skirting.
Also do not plaster all the way to the concrete floor. Leave a 25-50mm gap.

Does this sort of a project need to be cleared by building standards?

I understand that if 25% of the internal plaster is removed, then BC will need to be involved. They may insist on the replacement meeting current BRs.
But you ought to check on this. I'm only a DIYer.

You may be able to add more insulation in other elements of the building in order to compensate for little or no insulation in the walls., Discuss it with your architect or BC.

 

[fullern]

Thank you very much for taking the time to reply.

I should expand, we intend on using lime plaster or some modern type of thing with similar properties, all to try and provide breathability (the current state of the render etc just locks moisture into the home).

With regards to your point about ventilation; would creating a suspended floor on joists etc. with concrete foundations, be a better alternative? Here is no real ventilation in the house except trickle vents.

Could you expand on your point of using the walls and floors as a heat sink? The walls are constructed of two layers of granite rubble with smaller rubble sandwiched between the two. In total probably about a foot and a half to two feet thick. There is no insulation or dpm in the property. My desire is to have the lounge area fully insulated both the walls and floor and to stop the damp.

Finally why not plaster all the way down to the concrete? Is this to allow movement or something?

Cheers!

 

[baileysufc]

You never board or plaster to the floor as it stops moisture transfer from floor to wall and visa versa

 

[mointainwalker]

What is the exterior finish to the walls - important when talking about breathability.

Previous comment about heat-sink refers to using mass of building to store heat from whatever heating-method you choose, but this is not really relevant if you are going to insulate internally

 

[fullern]

The exterior is now lime rendered -spent the last four months doing that so looking forward to starting work indoors now! Makes sense about not plastering down to the floor, does skirting board not act as a bridge for moisture though?

Guess I had better check the bc regs and start looking at best materials for the job. Thank you all for your help, no doubt more questions will crop up as this progresses.

 

[RNReindeer]

about not plastering down to the floor, does skirting board not act as a bridge for moisture though?

Which is why I use a PVC or ceramic skirting material on lime plastered walls.

The ventilation referred to uninhabited properties.