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External Insulation on pebble dashed walls?

  • 14-02-2022 8:35pm
    Registered Users Posts: 1,972 ✭✭✭ gooner99

    Hi. My house has loose white bead in a 70mm cavity. I'm thinking of availing of insulation grants and was thinking external would be best.

    Can it be installed on dashed walls as shown in attached pictures?

    House is on an exposed west coast site about 50m to the sea. Not sure if this poses additional issues?

    I'm not familiar with EWI, so all advice most welcome.


  • Moderators, Society & Culture Moderators Posts: 33,540 Mod ✭✭✭✭ Gumbo

    Yes in my experience. I’ve seen it been done to many dashed walls here in Dublin.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    Yes it can, have it on my own rough dashed 70's house, however the devil is in the detail.

    Each insulation batt needs to be "buttered" continuously around the edges with adhesive thick enough to help prevent thermal looping from batt to batt at the back of the insulation ... not standard practice by the installers though unless specifically instructed to do so and supervised.

  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Mick what type and thickness EWI system did you apply?

    Did you install on a rail at damp proof level or go down to foundations and did you remove soffit and go above it?

    How are you finding it. Are you happy with the results?

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    200mm rockwool (breathable system), yes up past soffit to meet attic insulation and down 600 / 900mm below ground depending. Super result. You can read some details here.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

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  • Registered Users Posts: 8,913 ✭✭✭ Danno

    Thanks for this thread... was thinking of eventually getting external insulation on a very similar wall.

    Would it be better to remove the dash and go back to the scratch-coat? With extensions to the house front and rear, i'd only be doing upstairs and the whole gable end.


  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Brilliant Mick. Will take a look at that.

    Was it hard to get someone to do it like that. Most I've seen online seem to do it on a rail and stop at the soffit?

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    Yes, probably the most difficult aspect of the project was the effort needed to find the right contractor to take it on and do it right!

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    Likely not better, imo. What are you gaining by removing the dash?

  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Excellent read Mick. Great job.

    My house also has a 60-70mm cavity with loose bead. But it's only 50sqm in size. I plan to add and extension too.

    Do you think that I should have the loose bead removed and bonded bead installed?

    Do you have any details on how the EWI should be done properly?

    Do you think it's necessary to dig up floors and insulate?

    Do you still run the oil burner, or have you gone to a2w?

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  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    1. Do you think that I should have the loose bead removed and bonded bead installed?
    2. Do you have any details on how the EWI should be done properly?
    3. Do you think it's necessary to dig up floors and insulate?
    4. Do you still run the oil burner, or have you gone to a2w?

    1. Depends on the condition of the loose bead and whether any of it has been lost over time. Will you be replacing your windows as part of the upgrade? If you do then a lot of bead will be lost so this bead should be removed and replaced with bonded bead.
    2. There are a lot of detail needed to be worked through to get the optimum result for your property. A decent starting point is to read SR.54 (Code of practice for the energy efficient retrofitting of dwellings).
    3. Not necessarily if the ewi is detailed correctly (I modelled my house in PHPP to determine the required depth to go down with the ewi). This enabled us to stay in the house while the works were being carried out. Also, personally I don't like underfloor heating which often accompanies this type of work especially if a hp is part of the heating solution..
    4. Yes, still have the original conventional oil boiler... however I run it like a heat pump by throttling the output where my rads don't get hot (typically 40ºC when on) and burn very little oil... in fact our average oil consumption is bang on where the PHPP modelled it to be. When the time comes to replace the boiler, I'm not convinced a hp would be the best solution in our case even though we are hp ready.

    Finally, do not disregard the importance of excellent airtightness & ventilation as part of your overall solution.

  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Thanks Mick. Appreciate your time and knowledge on the subject.

    1. I'll likely change the windows as they are DG PVC about twenty years old, so probably will lose some bead. Will look at replacing with bonded.

    2. Thanks for the info. To me it's sounding like a difficult task for a lay person to get the detailing right. Seems like most will get stuck with the standard contractor install method. As you said in the passive House plus article you found it hard to find a EWI contractor that was willing to apply correctly?

    3. I am wary of A2W myself. Especially with the outdoor unit being situated so close to salt water. I have solid fuel fire and storage heaters ATM, so open to all options?

    4. Oil sounds like it's possibly still a good solution if the heat demand is low enough?

    5. Would I also be best to look at EWI on the extension or look at a different approach?

  • Registered Users Posts: 1,391 ✭✭✭ hesker

    Mick, how did you get the installer to agree to do it as you wanted. Did you have a written contract where you had the soffit and below ground detail specifically called out. Or was it just a verbal agreement with you inspecting as it progressed.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    In general for extensions where ewi was on the main building, my preference would be block on flat with ewi and internally finished with sand/cement/skim.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    The contractor I got would only do it the right way! When the soffit was removed, several corner box sections had to be repaired due to rot (not entirely unexpected). Verbal agreement and very regular (daily) checking of progress etc by myself.

  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Mick. Should I consider internal insulation as an alternative. Seems to be more experience in this Country with it. But I'm sure it has its issues too. One that springs to mind is loosing floor space and thermal store.

  • Registered Users Posts: 6,414 ✭✭✭ jhegarty

    I had the exact same pebbledash and it was no issue.

  • Registered Users Posts: 1,391 ✭✭✭ hesker

    For anyone wondering about EWI fitting process there is a guy doing it in Kerry who has a load of YouTube videos up showing how it’s done. No links as I don’t want to be accused of advertising anyone. He shows how to do above soffit level detail but I haven’t yet seen him go below ground.

  • Registered Users Posts: 1,391 ✭✭✭ hesker

    I’ve been looking up your guy but I don’t think he is set up as a one stop shop for SEAI grants. Might give him a call to check.

    I have deep soffits so have about 2 feet of internal wall above soffit. Every company that has visited has said they stop at soffit level. When I point out the massive cold bridge they go umm yeah….that’s not how we usually do it. So that’s why I was wondering about contracts. I will need to get this stuff nailed down.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan

    Imo and for multiple reasons discussed to death on this site in the past, no (unless there is absolutely no other option).

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  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Passive House academy shows the soffit detail on one of their videos on YouTube too. Hope it's ok to mention them.

  • Registered Users Posts: 1,972 ✭✭✭ gooner99

    Thanks Mick.

    It's a real shane that the correct soffit and plinth detail is not stipulated by the SEAI.

  • Registered Users Posts: 980 ✭✭✭ TimHorton

    Great read Mick, If you had the internal space and the 100mm cavity currently had 50mm Polyiso would you go with dry lining over EWI ? and I presume get the cavity filled no matter what option you go for?

  • Registered Users Posts: 30,845 ✭✭✭✭ listermint

    I've done self install of my bungalow three years ago now. 200mm EPS rail from dpc up and heavier gauge water repellent 180mm EPS below rail 600mm down, had to dig out around the house for that.

    Removed all sofits and repaired rot and replaced with Pvc including down pipes.

    I used a spray foam adhesive system and once set then drilled and fixed with thermal bridges fixings finally capped with EPS caps.

    Forgot I brought all windows out into the insulation later by 100mm boxed out as I was having windows replaced at the time. Old timber frames single pane glass came out.

    Had a plasterer do the bond coat and mesh and then final acrylic coat as I'm simply not a plasterer more organised grunt work.

    Took about a month to complete as its not small bungalow.

    The quotes at the time were laughable and no one was going below ground and up to soffit installs. So I said fk it il do it myself. Cost me 12,5k start to finish. my labour excluded.

  • Registered Users Posts: 2,707 ✭✭✭ MicktheMan