Timber I beam construction longevity.

[bissoejosh]

  On 15/12/2019 at 18:11, ProDave said:

Why would you have no insulation between the studs?  do you want a cold house?

 

The VCL would surely go on the inside of the frame? (mine is as I think everyone else)

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Keeping all the timber warm with external insulation. Minimises condensation risk I guess and gives a huge service void. Fixing a suitable amount of external insulation might be tricky though. 

 

http://mattrisinger.com/joe-lstibureks-perfect-wall-concept-the-500-year-house/

[gavztheouch]

Bissoejosh, yeah it was on Matt Risinger's youtube channel I seen this concept of insulation on the outside of the building. Someone took it a stage further and didn't drywall the inside leaving the studs exposed a very specific look which I quite liked once it was all painted the same colour inside. The benefit was the wall could be maintained and any water ingress would be obvious.

 

https://risingerbuild.com/mesmerize/perfectwall/

Edited December 15, 2019 by gavztheouch

[Patrick]

Liked it as well but is probably Impossible to get past building regs this side of the ocean.

[Russell griffiths]

Getting back to the original question on i joists, I have i joist off cuts that have been sitting in a pile for over 6 months out in all this rain and they look perfect. 

[ToughButterCup]

  On 16/12/2019 at 01:12, Sensus said:

[...]

Using the same approach on a wall means that you are entirely reliant upon the integrity of the VCL, and we all know where that will end...

[...]

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A really interesting post. Thanks.

Could you expand on the issue of VCLs and (lack of?) integrity over time. Are you hinting that there is an issue with all VCLs, or perhaps that over time VCLs get punctured or fail in some way and so their performance is degraded?

[ADLIan]

Difference with a flat roof is the waterproof membrane/layer which invariably has a massively high vapour resistance but is on the cold side of the insulation. This situation should not arise with TF walls.

[ProDave]

  On 16/12/2019 at 01:12, Sensus said:

 

This touches on the very valid point that placing insulation between the timber frame studs is essentially analogous to a 'cold' flat roof construction, turned through 90 degrees.

 

...And you won't find a single professional who will advise that a 'cold' flat roof is technically superior to a 'warm' one. We only ever use 'cold' flat roof construction where it is forced upon us because there is no alternative (usually due to constraints on thickness). Using the same approach on a wall means that you are entirely reliant upon the integrity of the VCL, and we all know where that will end...

 

Of course, if you're going to fix the insulation on the outside of the frame, there's no point in using I-beams - they're not required, structurally; they're much more expensive, and the only reason we usually use them is to provide a greater thickness for insulation and reduced thermal bridging when you're insulating between the studs.

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So what do you describe a wall and roof construction, where it is insulated outside the frame AND between the studs of the frame.  I have always called that a warm wall / roof.

 

I see many old timber framed properties, that are insulated between the studs, without any VCL at all, and I have yet to find one that is showing any signs of dampness let alone rot in the frame, so  I suspect this is a theoretical problem that just does not happen in real life.

[scottishjohn]

  On 16/12/2019 at 09:04, ProDave said:

see many old timber framed properties, that are insulated between the studs, without any VCL at all, and I have yet to find one that is showing any signs of dampness let alone rot in the frame, so  I suspect this is a theoretical problem that just does not happen in real life.

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maybe these houses have plenty of drafts to stop any build up of moisture and the dreaded mould.

I can say my 700,s Tf is built like that --outer brick skin --draft from top to bottom up the void between outer brick skin and innner wood frame 

 the vapour barrier was fitted directly behind the inner osb sheeting behind the plaster board.

wall is  brick +gap ,then osb , then tinber frame ,osb again ,then vcl ,then plasterboard.

top of wall open to loft with ridge vents.

I tried blocking the wall head up --one winter and Osb sheeting on inside of roof on north side of house started to turn black 

unblocked wall head --all stopped .

 so yes it can be fine but needs good draft up void between outer skin and Tf osb

[ProDave]

  On 16/12/2019 at 09:26, Sensus said:

 

I have seen plenty.

 

Sometimes it happens, sometimes it doesn't. It's all about acceptable levels of risk.

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I see plenty of mouldy lofts where warm air is getting into the loft, but what I was meaning is when cutting a hole for a switch or socket, or just removing an existing one, it is very rare to see any signs of distress in the timber frame exposed or OSB (or plywood) layer.

[ToughButterCup]

@Sensus, I do remember a post by @Jeremy Harris a year or so ago explaining exactly the process you outline above.

This may be the post - about that good old friend interstital condensation. There are some others too..... Here's the search I did on the matter

[ToughButterCup]

  On 16/12/2019 at 09:49, ProDave said:

[...]

it is very rare to see any signs of distress in the timber frame exposed or OSB (or plywood) layer.

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I suspect you mean distress local to the cut (you?) made Dave.

And I think what @Sensus might be emphasising is the risk to the sole plate from water trickling down inside the timber frame. Or have I misunderstood?

[scottishjohn]

  On 17/12/2019 at 15:55, AnonymousBosch said:

@Sensus, I do remember a post by @Jeremy Harris a year or so ago explaining exactly the process you outline above.

This may be the post - about that good old friend interstital condensation. There are some others too..... Here's the search I did on the matter

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a whole row of  terraced houses built here recently 

TF and on outside 300mm of polystrene blocks were attached ,then rendered -

looked silly when they were building it 

roofs were made up on ground +tiled ,then lifted up and dropped on top of walls ,

very strange way to build,but no scaffolding !! but they had cranes on site 

time will tell if works

 

Edited December 17, 2019 by scottishjohn

[BotusBuild]

  On 16/12/2019 at 09:22, scottishjohn said:

I tried blocking the wall head up --one winter and Osb sheeting on inside of roof on north side of house started to turn black 

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The same happened to us when the cowboys came round and put in 300mm of rockwool insulation in our loft, effectively blocking the draft up the gap into the loft. As the rockwool has settled it has got a little better, but we still suffer a little.

[scottishjohn]

  On 17/12/2019 at 16:37, BotusBuild said:

The same happened to us when the cowboys came round and put in 300mm of rockwool insulation in our loft, effectively blocking the draft up the gap into the loft. As the rockwool has settled it has got a little better, but we still suffer a little.

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just get in there and pull it way from wall head so it can breathe

[BotusBuild]

  On 17/12/2019 at 16:42, scottishjohn said:

just get in there and pull it way from wall head so it can breathe

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I know, I know, just can't find a Round Tuit ?