Cement on old stone and rubble walls - remover or leave?

judesherry

Hi,

I am renovating an old terraced house (1850's) that's made up of 600mm stone and rubble walls. I assume its lime mortar (see photo). It's covered internally with cement what appears to be (see photo) and externally with what appears to be cement pebbledash. The floors also appear to be cement.

There is no evident damp besides leaks in the roof.

I will be replacing the roof and including insulation, replacing the windows and external doors as well as underfloor heating with a heat pump. I also want to externally insulate the walls as the interior of the house is quite small.

My questions is - if the house fabric is made airtight and fully insulated will the moisture in the walls start to cause problems if a non-breathable insulation is used and if the cement is left on.

I have received contractionary information from contractors so not sure where to turn to for expert advice.
As there is no damp will a damp expert help?

Thanks for any thoughts or experiences

BryanF

What’s the ventilation strategy? What’s the proposed wall build-up? Will the insulation be entirely continuous?

Question can’t be answered with info provided. Have you considered hiring someone other than a contractor to advise?

judesherry

The ventilation system will be determined once we know the airtightness we can achieve with the windows, doors, and insulation. We have a ventilation expert who we will work with, to design the best options - most likely an MVHR.

The wall build up will also depend on the insulation choices suitable to stone and rubble walls - my main question is if the current cement (internally and externally) will need to be removed. it is not possible to have it continuously insulation as the house is terraced and we do not want to loose space or the heat retation of the stone walls with internal insulation.

Indeed we have considered and have contacted damp experts but with no current signs of damp their services are not required. We have contacted SEAI approved retrofitting experts who have said they have no insulation solutions for stone and rubble walls. What type of experts would recommend?

BryanF

judesherry wrote: »

1. if the house fabric is made airtight and fully insulated will the moisture in the walls start to cause problems
2. if a non-breathable insulation is used and if the cement is left on.
3. contractionary information from contractors expert advice.
4. As there is no damp will a damp expert help?

judesherry wrote: »

5. The ventilation system will be determined once we know the airtightness we can achieve with the windows, doors, and insulation.
6. We have a ventilation expert who we will work with, to design the best options - most likely an MVHR.

7. The wall build up will also depend on the insulation choices suitable to stone and rubble walls - my main question is if the current cement (internally and externally) will need to be removed.
8. it is not possible to have it continuously insulation as the house is terraced and
9. we do not want to loose space or the heat retation of the stone walls with internal insulation.

10. Indeed we have considered and have contacted damp experts but with no current signs of damp their services are not required.
11. We have contacted SEAI approved retrofitting experts who have said they have no insulation solutions for stone and rubble walls.
12. What type of experts would recommend?

1. Possibly. You need to factor in a lack of DPC & separately how internal moisture is managed, reducing additional moisture entering the walls.
2. Assuming external wall insulation, this may be less of a concern. But continuity of insulation in a terrace + ground & eaves should be a concern.
3. Contractors are not experts in interstitial condensation. Contractor should follow design drawings & specs or at a minimum EN certified data sheets of manufacturers systems suitable for the situation.
4. are you confusing damp (rising damp or weather issue) with interstitial condensation (caused by lack of breathability or continuous vapour barrier preventing moisture entering the wall)
5. Well then, work that detail out, set a target and make a decision
6. As per 5.
7. Work out all junction details, determine due points, ensuring continuous insulation. When you done that, assuming you cant achieve continuity, consider a breathable EWI system. And hack of the cementitious renders
8/9. Sounds like you’ve answered point 7.
10. As per 4.
11. SEAI experts! LOL
12. Breathable external wall system manufacturer, qualified arch/ arch tech/ surveyor dealing with old buildings.

judesherry

Thanks for the very detailed and helpful response. Will take it all on board.