Most effective fix for insulation problem identified on newly constructed area...

chipstick2

Hi, we just had a professional snag list completed on our new attic conversion and we're told we have a big problem on our hands with the ceiling insulation installed in this new attic room. We have a meeting with the builder this week and in advance of that we are trying to consider/understand what effective, potential solutions are open to us to remedy the problem and which type of professional to engage to confirm the underlying issue and prescribe the best potential solution.

The problem identified in the Snag List is as follows, the felt on our roof is the old fashioned NON-BREATHABLE type. Directly below that the builder has filled the rafter area with 100 mm/6 inch of rockwool insulation. The rafters are 100 mm / 6 inch deep so the wool is snug to rafter and felt. The next layer below this rockwool is a 38mm warm board which is skimmed and that forms the ceiling of the attic room. So the issue is the rockwool is snug to the non-breathable roof felt. Our surveyor's opinion is that there should be a definite layer of air between the rockwool and the felt. Otherwise it is only a matter of time before condensation will cause the rockwool to get wet and result in the bad double-whammy of the rockwool losing it's insulation properties and worse-still the damp causing the roof-timber to rot, making the roof unstable. My guess is the builder feels there is sufficient minimal air flow around the wool to prevent condensation even when the wool is against the NON BREATHABLE felt.

My queries are:

- We are making the assumption that the professional reading of this problem on the Snag List is correct and we are trying to focus on what might be both the most effective, least arduous way possible to solve the problem. What 're-fit' or remedy, if any, can be applied to the existing insulation short-of taking down the attic ceiling and starting again from scratch. This time possibly with 50 mm kingspan sheets instead of the rockwool placed in the 100 mm rafter-space with a definite air pocket between the new insulation board and the roof felt.

- My guess is that the builder will suggest a 'solution' that is offers him the quickest, cheapest route to completion. Possibly trying to remove the sheets of rockwool from the sides in the eaves and then slide the 50 mm kingspan boards blindly up into that gap from the side in the eaves. What is yr opinion on the effectiveness of this option. My concern is that either the rockwool will not come out cleanly leaving bits behind and/or worse still that the 50 mm kingspan boards will not slide-up properly into this blind-space resulting in gaps in the insulation and cold spots in the room. I would imagine the very act of sliding these boards up will mean the boards are not snug to the edges of the rafters as they should be.

- Can an architectural tech / engineer / surveyor be engaged to confirm the risk already identified so that the builder cannot deny validity of the risk and also which professional is best to engage to suggest an effective fix for the insulation problem.

As the final payment is still owing to the builder he will probably insist that it is himself who should execute the proposed fix in order to recoup the final part of his fee. In this instance I would have understandable concerns that the builder would cut further corners and continue to overlook errors in order to complete the job as quickly as possible. We are not construction-minded and of course an A.T or a surveyor can only be on-site so often or check so much..Once the ceiling is plastered how can we/the A.T/surveyor know whether the refit has been done properly this time.

Thanks in advance for any insight people may be able to share with this. Very much appreciated.

4Sticks

The legal obligation is on you the building owner to get it right. That is not a rebuke , intended to be unhelpful but is is simply the bald legal principle. Never lose site of this. If the problem is not solved no one but you as building owner is the primary culprit in law who may in a secondary action only seek to "share the pain"

The problem you have is of such a fundamental nature no one who calls himself a builder should have done this.
In my opinion is his ignorance of or contempt for a very basic building regulations requirements means you owe him nothing and in fact you should put him on notice that you will seek another to carry out the required remedial works and seek compensation from him for the additional expense.

From your question you already know the construction technical answer. Your roof timbers must be stripped bare.

chipstick2

Hi 4sticks, many thanks for taking the time to reply. Very much obliged. Of the professions listed (A.T, surveyor, construction engineer), who in this instance has the most appropriate skillset to oversee the remedial works required in this case?

4Sticks

AT.

Mellor

chipstick2 wrote: »

My guess is the builder feels there is sufficient minimal air flow around the wool to prevent condensation even when the wool is against the NON BREATHABLE felt.

My guess would be that he didn't give air-flow a seconds thought.

As for the solutions mentioned, sliding them up from the side/eaves is not an option, could potentially end up being worse than current.

IMO, you have two options;

1. Strip the Ceiling. And relay suitable insulation
2. Strip the roof. And relay breathable felt.

chipstick2

Mellor, thank you very much for your reply. Most appreciated. The builders have suggested that they can put additional vents on the ext of the roof area between each pair of rafters to increase the airflow through the rockwool. Again this sounds to me like a make-shift 'fix' based on the clear advice from yourself and 4sticks. Can I ask though - and again please excuse my ignorance - is it a case that this would aid the required 'airflow' but would also introduce undesired additional drafts as a serious downside. Are there other considerations that I am overlooking which are also relevant to this suggestion. If this is not a runner I want to refute the idea with the hard facts as to why this would not work. Thank you.

4Sticks

Worse worse worse. What the builder is proposing would not introduce enough airflow but only locally degrade the thermal insulation , thereby reducing surface temperatures and increasing the risk of condensation. This is not a builder no matter he may drive a white van read the Sun and smoke roll-yer-owns.

You need vents top and bottom and a 50mm vent space between. And board type insulation that will not degrade with the necessary airflows.



Or you will get this

Mellor

chipstick2 wrote: »

The builders have suggested that they can put additional vents on the ext of the roof area between each pair of rafters to increase the airflow through the rockwool.

I agree with 4Sticks. This is not a solution.
The purpose of the gap is for air movement along the outside of the rock wool. Not through it. These vents won't provide that, only provide localised cold spots.

chipstick2

Yikes, am filled with unprecedented mixture of gratitude for yr invaluable information and just plain horror over the mess that is now to be dealt with.

Pease feel free to pm me contact details for either yourselves or another appropriate A.T that we could employ to oversee the rectification of this situation.

Finally, ballpark figure-wise, what is a likely cost comparison between the two remedies suggested by Mellor (a Re-felt VERSUS ceiling-down with re-insulaion using board).

Thanks for taking the time to fill me in.

4Sticks

Where do you live ( town/county)

BryanF

chipstick2 wrote: »

is it a case that this would aid the required 'airflow' but would also introduce undesired additional drafts as a serious downside.

thats what the vapour barrier doubled as an air-tightness layer on the warm side of the insulation is for. did they put this in?

4Sticks

I recommend to engage a solicitor too. In conjunction with your AT s/he needs to carefully legally dispose of your "builder"

chipstick2

Thanks. I will forward location details by PM if that's okay.
Re: vapor barrier, I requested it and was told it would cause sweating which would drench the wool. So it was not fitted.
Unfortunately I have to go offline shortly for an hour or two but I will get back online as soon as i can and will get any other posts/PMs then. The feedback/info is much appreciated. And that shocking picture posted is very hard to argue with! Thanks all.

4Sticks

chipstick2 wrote: »

Re: vapor barrier, I requested it and was told it would cause sweating which would drench the wool.

Yipeekayay.

BryanF

chipstick2 wrote: »

Re: vapor barrier, I requested it and was told it would cause sweating which would drench the wool. So it was not fitted.

yee haw

4Sticks wrote: »

I recommend to engage a solicitor too. In conjunction with your AT s/he needs to carefully legally dispose of your "builder"

i have to agree

OP
when your finished with this process come back and tell us would a professional have saved you time/ money/stress in the long run and if you were doing it again would you have employed an architect / AT to detail/ certify the works

BTW how did the 'snagger' cop that there was no gap for ventialtion can we assume a section was left open for this checking process?

given that there is no Vapour barrier - it think you should remove the plasterboard and insulation from the inside and fit vents, reinstall insulation with suitable gap and re plasterboard.

chipstick2

Thanks. Yes. Am happy to follow-up. Just wondering could you give a very approx ballpark idea of a fee-scale for the AT work needed on the management of this process. And a very approx figure for the construction re-working req'd. I understand such an estimate would be a broad one in the absence of the exact specifics but it would serve as a useful starting point for my initial budget for the project/pickle ahead. Thank you.

4Sticks

Stabbing in the dark ...

AT €1~2k. Depends on how much time is spent "disposing" of the first "builder". Do not under estimate the importance of this. Don't find yourself successfully sued even by a cowboy because you did not follow a documented-to-be-fair due process.

Budget €75/90 m2 of affected wall/ceiling surface area of internal attic to be stripped and re done. Not allowing for any electrical or plumbing or skirtings or rads or curtain hanging complications