Internal Finish to externally insulated wall

kilclon

Hi,

I am planning on externally insulating my 2 storey over basement mid terraced house. Thinking of using a mineral wool system.
The external walls of the house are stone from basement to ground floor level and brick from ground floor up to eaves. They are solid walls and start at around 450mm thick in basement going to around 300mm at 1st floor level.

How would I best finish the walls internally. Would you use a different system on the external walls than on the party walls? The walls are currently stripped of the lime render which used to be on them.
I was hoping to dab and slab them but am not sure if this will be the best thing with regard to breathability etc.
Also, is this type of EWI suitable for this type of building?

Cheers.

sydthebeat

breathability on an EWI building is of much less significance because your warming the whole wall up to a temperature which is above the dew point.

Ensure the rooms have adequate background and rapid ventilation.

Personally, if it was possible, id try to expose the brick finish internally, and repoint. this could take a large amount of work though, depending on the condition of the brick. This may be aesthetically pleasing in rooms which would have one brick feature walls.

Otherwise dot and dab plasterboard is fine, if the walls are square and plumb.

kilclon

sydthebeat wrote: »

breathability on an EWI building is of much less significance because your warming the whole wall up to a temperature which is above the dew point.

Ensure the rooms have adequate background and rapid ventilation.

Personally, if it was possible, id try to expose the brick finish internally, and repoint. this could take a large amount of work though, depending on the condition of the brick. This may be aesthetically pleasing in rooms which would have one brick feature walls.

Otherwise dot and dab plasterboard is fine, if the walls are square and plumb.

Thanks.
I also like the idea of an exposed brick wall. Unfortunately they aren't in a good enough condition and I think they would require too much work.
Would you use a regular skim finish on the plasterboard?

In the basement the walls are stone and pretty rough. I intend to tank them with k11 or something similar. I have already underpinned the basement walls in order to gain extra ceiling height. Haven't poured the floor yet. The rough walls will have to be smoothed out in order to take the tanking. Would sand and cement be suitable for this or would a lime plaster be required?

kilclon

Re-reading your post leads me to believe that using sand and cement would not be a problem as the walls will be warmed to a level above the due point. Would this be correct?
Thanks

BryanF

there are different 'plasterboards' available for your situation, farmacell for instance have a product that would be more suitable

If you go for plaster, reinstate the lime IMO

BryanF

Earlier, Op you asked about ewi, and what to do at gf junction and basement? do you use the basement? Is it damp? What ventilation strategy is proposed?

kilclon

BryanF wrote: »

Earlier, Op you asked about ewi, and what to do at gf junction and basement? do you use the basement? Is it damp? What ventilation strategy is proposed?

Yes the basement will be used. We have lowered it from a 2m ceiling height to 2.4 to make it more useable. The basement was damp but just yesterday I had chemical doc injected (not sure if this will work but wasn't excessively expensive when the walls were already exposed). I also intend on tanking the walls up to 1.5m above ffl. Ffl in the basement is about 400mm below ground level outside generally so the ewi will come down to this level, except for half of the wall at the rear of the house where we built an extension at gf return level. I used bituthene 8000 on the wall with 100mm of eps before backfilling.

I had intended using trickle vents in the windows and wall vents where required for ventilation?

BryanF

Re basement: I'd probably consider a metal frame drylining system, contious of where the due point will be.
Re ventilation: I would install several RH sensors in different parts of the house, and certainly consider some form of mechanical system
Re ewi : agree and carefully detail window, wall and roof junctions - thermal bridging

kilclon

BryanF wrote: »

Re basement: I'd probably consider a metal frame drylining system, contious of where the due point will be.
Re ventilation: I would install several RH sensors in different parts of the house, and certainly consider some form of mechanical system
Re ewi : agree and carefully detail window, wall and roof junctions - thermal bridging

I had been leaning away from drylining the basement because the house has been subject to flooding in the past as a result of sewage backflow. Although I think I have taken the necessary steps to prevent this from happening again, I won't know for sure until there is some sort of flooding event.
If this is was a concern, would you still recommend the metal frame system?

BryanF

I'd take a holistic view with specialist consultants. Flooding and sewerage etc canbe dealt with by the use of tanking and specialist systems.
I can't comment further without knowing the job in detail, but it seems your not confident in the tanking your using?

kilclon

BryanF wrote: »

I'd take a holistic view with specialist consultants. Flooding and sewerage etc canbe dealt with by the use of tanking and specialist systems.
I can't comment further without knowing the job in detail, but it seems your not confident in the tanking your using?

I wouldn't say its a lack of confidence, but more overly cautious. I don't think tanking the walls is necessarily required, just an extra safeguard should the chemical dpc fail. I have installed non return valves where required and have a sewage lifting station with built in floor drain for the basement bathroom. This discharges to a separate sewer line which is above surcharge level.
I sealed the underpin joints with a bentonite strip and this seems to be preventing any ingress of ground water through the walls. I will seal the floor to the walls in a similar way.
I definitely think the basement should be dry but there is always that little doubt in the back of my mind and iwas wanting to prepare for the worst (without going overboard as cost is an issue).

kilclon

I haven't actually chosen my EWI installer. Everyone feel free to p.m. me recommendations of companies who know what they are doing in the Dublin region.
Thanks.