Do I need a vapour barrier

Jambo

Hi All,

Currently getting a Timber Frame extension built and the Builder is recommending no vapour barrier yet some folk are telling me I need one

My construction knowledge is almost nil so my question is do I need one ?

Please Forgive my lack of construction terminology but but the construction detail from the outermost layer to innermost out as currently planned / partially built is as follows

1. Concrete Render
2. Concrete Scratch Coat
3. 100mm Solid Concrete Blocks
4. 50mm Cavity / Gap
5. Fakro Eurotop (green)
6. 12mm Marine Ply
7. 100mm x 50mm Studs (Packed with 150mm rockwool)
8. 12mm Marine Ply
9. 50mm Insulated Slab
10. Plaster Coat

From what I can see the existing house is more or less the same construction
with the exception that it has no insulated slab and has osb board rather than marine ply.

Any advice would be appreciated

BryanF

Is he taping/sealing the marine ply joints for vapour control (and air-tightnes)

And do note that's Very little insulation, skirting the max U-value your aloud in an extension

If that was a new build there would be a thickness of 200mm mineral wool (approx)

I would suggest a 150 stud/insulation with vapour varrier taped and sealed on the inside.


Question,
does your house suffer from drafts?
What size is the extension?

Jambo

BryanF wrote: »

Is he taping/sealing the marine ply joints for vapour control (and air-tightnes)

And do note that's Very little insulation, skirting the max U-value your aloud in an extension

If that was a new build there would be a thickness of 200mm mineral wool (approx)

I would suggest a 150 stud/insulation with vapour varrier taped and sealed on the inside.


Question,
does your house suffer from drafts?
What size is the extension?

BryanF thanks for your reply.

Did you mean to say we are skirting the min u value rather than max?

Re your Questions
What size is the extension?

Extension is 7m x 4m (external) and divided internally into one large and one box room. Large room has an open ceeling 3m at the apex.

Does your house suffer from drafts?

The existing house doesn't suffer from drafts bar one room where u can feel a slight draft in very high winds along a very small section of skirting board along a bay window, and at that you have to have your hand on the floor to feel it. The existing house is in s somewhat exposed location is warm house , it heats quickly has a "c" BER Rating and.

At present the outer brick, outer ply, green membrane , studs and roof joists are up already.

Ref taping of ply, on the external set of ply this has not been done and I would say 50% of all joints are now behind the noggins, All the visible joints are very tight.

I forgot to mention he is going to pack in 150mm rockwool into the 100mm wall stud.

Additional to my original post open ceeling will have 100mm of kingspan .

BryanF

What has your architect specified, and who is certifying your project complies with building regulations ?

You need a vapour barrier on the inside- taped & sealed, wall, window, penetrations & ceiling

No point stuffing 150mm insulation into a 110 stud frame

I'd be concerned the builder is back in 2000, check the homebond book in his van is the latest addition.

Lower the u-value the better the insulation properties are. The insulation levels stated are not good

sydthebeat

so... this is a DIY timber frame construction?

whos certifying this??

Jambo

BryanF wrote: »

What has your architect specified, and who is certifying your project complies with building regulations ?

You need a vapour barrier on the inside- taped & sealed, wall, window, penetrations & ceiling

No point stuffing 150mm insulation into a 110 stud frame

I'd be concerned the builder is back in 2000, check the homebond book in his van is the latest addition.

Lower the u-value the better the insulation properties are. The insulation levels stated are not good

@BryanF

We only went with outline / sketch drawings. We did not opt for certification - I had understood that this was only required for non exempt construction.

Back to the drawing board I guess - hopefully retrospective certification may be open to us as I have taken 1000s of photos of every stage and detail for my own records.

Jambo

sydthebeat wrote: »

so... this is a DIY timber frame construction?

whos certifying this??

I have just read SI 9 of 2014 and the requirement for certification in relation to extensions appears to only apply to extensions that are over 40sqm, where as my internal floor space is well under that limit.

No this is not a DIY build

sydthebeat

Jambo wrote: »

I have just read SI 9 of 2014 and the requirement for certification in relation to extensions appears to only apply to extensions that are over 40sqm, where as my internal floor space is well under that limit.

No this is not a DIY build

those are the BUILDING CONTROL REGULATIONS

NOT

the BUILDING REGULATIONS

you are still required to build in accordance with the building regulations, and you should have someone to certify this for you.

I realise its convoluted, welcome to our world......

BryanF

Jambo wrote: »

I have just read SI 9 of 2014 and the requirement for certification in relation to extensions appears to only apply to extensions that are over 40sqm, where as my internal floor space is well under that limit.

No this is not a DIY build

Look at all the threads of people trying to sell/ borrow/ settle their affairs who need to retrospectively get certification.

My advice, employ a local PI insured arch or eng now to sign off you build complies with building regulations . Photos are of no interests to bank/purchaser/building control