Old Stone Wall - Radon Barrier and Condensation

tails_naf

Hi All,

We are renovating an old house with 1m stone walls. The main issue with these renovation jobs is the dreaded condensation and required breath-ability of the walls. However, when it comes to the floors, given radon is a gas, it would seem breathability may be something to be avoided.

So what is the recommended solution to this?

My feeling is that a standard DPC+Radon barrier should still be installed, but it would be sealed to the walls internally at floor level, instead of being passed out through the (non-existant) blockwork.

This image shows how the floor/walls look now - basically timber with a void/floor-timbers beneath it.



The proposed floor build up, with DPC/Radon in red is shown here:


Do you think this is reasonable? From what I can see, this floor make-up should be ok, despite the walls having to be treated differently from block-built.

For what its worth, the wall make up internally will likely be breathable insulation against the stone, with breathable air-tight membrane next (sealed to floors and around opes), and finally breathable plasterboard. Outside will be lime render.

Any help would be greatly appreciated.

BryanF

There are lime / Leca treatments available

Have you checked the radon maps?

Will you have mech ventilation system ?

Have you decided on rising damp in wall solution? Electro osmosis or chemical injection.. EO gets my vote

Markcheese

We got our house tested for radon before we did work ... the extension on the back has radon barriers and sump but we left the floors alone in the old house as the radon tests showed nothing to worry about...

tails_naf

BryanF wrote: »

There are lime / Leca treatments available

Have you checked the radon maps?

Will you have mech ventilation system ?

Have you decided on rising damp in wall solution? Electro osmosis or chemical injection.. EO gets my vote

Hi Bryan,

Thanks for the reply. The lime/Leca, is this specifically for floors, or are you referring to walls? The wall aspect we are not as worried about - it is really the floor make-up that we want to ensure is ok.

The radon maps are pretty coarse, so not sure how much trust I'd put in them, but this region looks high.

Mech Ventilation will be provided.

As for the rising damp - our understanding was going the breathable route would/should prevent this? If not - why go to the bother/cost of making the wall breathable in the first place?

tails_naf

Markcheese wrote: »

We got our house tested for radon before we did work ... the extension on the back has radon barriers and sump but we left the floors alone in the old house as the radon tests showed nothing to worry about...

Hi Mark,

Did you do anything to the air-tightness of the old part? Of course it adequate ventilation it should be ok. We also want to have the floor insulated, so ideally using a standard floor build up, including DPC/Radon barrier is a runner.

Markcheese

We didnt do much with airtightness in the old house..(tape doors and windows ect.) If I had a floating floor not concrete , I think I'd have that redone and insulated well -and if the void under the floor is vented that should help get rid of any radon .
Google radon testing -its about 50 quid, they post it out ,you place it and post it back about a month later..
If you dont have a damp problem do you need to do damp proofing . Can it be retro fitted ?

One thing I will say ... stone houses work best with a slow steady heat source . Since we put a stove in the sitting room the house performs much better, pretty much heats the whole house , light it in the morning keep it going low and slow... we're averaging a half a bag of coal a week

BryanF

tails_naf wrote: »

Hi Bryan,

Thanks for the reply. The lime/Leca, is this specifically for floors, or are you referring to walls? The wall aspect we are not as worried about - it is really the floor make-up that we want to ensure is ok.

The radon maps are pretty coarse, so not sure how much trust I'd put in them, but this region looks high.

Mech Ventilation will be provided.

As for the rising damp - our understanding was going the breathable route would/should prevent this? If not - why go to the bother/cost of making the wall breathable in the first place?

No point sorting the floors if the damp just rises up the walls

You need to think about the walls and floors at the same time.

Lime Leca for the floor, There are specific breathable floors with radon solutions available from several specialist sustaiable building companies, but you will pay a premium for this.

Re breathable wall constructions. You must still treat the rising damp separately IMO, ideally below or at the level of radon/dpc

Edit: are you going with underfloor heating? You had better take a step back and work out the floor to wall junctions carefully before going any further.

tails_naf

BryanF wrote: »

No point sorting the floors if the damp just rises up the walls

You need to think about the walls and floors at the same time.

Lime Leca for the floor, There are specific breathable floors with radon solutions available from several specialist sustaiable building companies, but you will pay a premium for this.

Re breathable wall constructions. You must still treat the rising damp separately IMO, ideally below or at the level of radon/dpc

Edit: are you going with underfloor heating? You had better take a step back and work out the floor to wall junctions carefully before going any further.

Hi Bryan,

We certainly are thinking about the walls - thanks for the pointers with regard to rising damp solutions - I'll take a look at them.

However, when it comes to the floors, is there anything fundamentally wrong with what I've proposed here? Is there a reason the floor MUST breathe?

Regarding the UFH, we will separate the floor-slab from the walls with 30-50mm of insulation to prevent cold bridging.

BryanF

tails_naf wrote: »

Hi Bryan,

We certainly are thinking about the walls - thanks for the pointers with regard to rising damp solutions - I'll take a look at them.

However, when it comes to the floors, is there anything fundamentally wrong with what I've proposed here? Is there a reason the floor MUST breathe?

Regarding the UFH, we will separate the floor-slab from the walls with 30-50mm of insulation to prevent cold bridging.

The floors do not have to breathe

30 even 50mm thermal insulation is not adequate IMO - this is part of the reason many ufh systems put in during the boom are expensive to run.

Re floor: provide radon sump and vents, external French drain on 4 sides of house, radon barrier terminated and considered with electro osmosis system

Calahonda52

IMO, even IMHO, there are two separate issues here:
one is about radon and the other about UFH, coupled with internally breathable this and that and external lime render.

The radon should be dealt with separately: address it and get on with it. End of.
The Radon map is based, AFAIR, on samples from the grid squares, coupled with geological data, as opposed to anything more accurate

Now you seem to have decided on UFH etc.

What about vented EWI coupled with a good quality MHVR? and what my learned co-member Bryan has suggested re EO

You will never 100% sort the rising damp so embrace it and use the MHVR to shift the air and forget about UFH and use the thermal mass of the walls?

This
https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx
might help and
there is a lot of stuff http://www.josephlittlearchitects.com
eg http://www.josephlittlearchitects.com/articles
on old walls/lime render /etc

In summary, my suggestions are to do the least with the existing and use modern technology to help as opposed to saying to a 1 m wide wall: " I am going to sort you."
It was there before you and will outlive you!
Keep well and think outside the box

MicktheMan

Calahonda52 wrote: »

What about vented EWI

What's that?

THE DON FANUCCI

BryanF wrote: »

There are lime / Leca treatments available

Have you checked the radon maps?

Will you have mech ventilation system ?

Have you decided on rising damp in wall solution? Electro osmosis or chemical injection.. EO gets my vote

is radon barrier and radon sump compulsory for every build? or only in Radon areas??

Gumbo

THE DON FANUCCI wrote: »

is radon barrier and radon sump compulsory for every build? or only in Radon areas??

In Dublin I expect to see it wverywher, even in extensions. Mostly do.

BryanF

THE DON FANUCCI wrote: »

is radon barrier and radon sump compulsory for every build? or only in Radon areas??

Everywhere but the op question was about old stone walls, there are remedial solution accepted by building control in these instances.