Big Neil

Inner Skin (thin-Joint Vs Timber Frame)

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At the moment i'm not too interested in the cost aspect given the almost infinite variables involved, more interested in the comparative reasons for using one system over another in certain circumstances.

 

To start with, whilst there seems a lot of manufacturer based evidence that it should be structurally safe to 'throw' up the inner skin in thin joint, including any floor joists and internal walls (imagine just the downstairs ones in this example and that they are also thin-joint block work), and then get the roof on before having started the outer skin, it seems like very few people either on here or other forums, are in favour of this. Compare this to timber frame however, where everyone almost immediately espouses it as a great system if you want to get to room height quickly, and then put the external skin up later

 

WHY? And in any answers lets assume for the sake of argument that the team using the system is experienced in using it, all relevant plant and materials are ready on site, and weather is nominally fine.

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For me the key is the ecology of timber frame over masonry builds which also impact the foundation design and the way that things like air tightness and insulation can be deployed to ensure an energy efficient building.

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For me it's the way it's a fair bit simpler to get all the critical detailing right so as to remove or reduce thermal bridging with a structural timber frame.  A well-designed timber frame built on an insulated slab solves one of the more awkward thermal bridging problems, the wall to floor junction, pretty simply.

 

Systems like ICF and Durisol can give a similar advantage, and can also go up pretty quickly, too.

 

 

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For me it would be second fix and services

timberframe on my last place was very easy to work with, easy to run services, easy to fix to, easy to insulate 

another is timber frame can be altered fairly easily, it can be very easy to stand in a room and think I wish I had made the ensuite a bit bigger, in timber I found it easier to adapt than blockwork. 

 

For reference 

1st build. brick n block

2nd build. timber frame

3rd currently in progress. ICF with timber internal walls. 

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3 hours ago, Big Neil said:

WHY? And in any answers lets assume for the sake of argument that the team using the system is experienced in using it, all relevant plant and materials are ready on site, and weather is nominally fine.

 

 

I remain puzzled and doubt you will get a balanced opinion from a British based forum because for some reason thin-joint never reached a critical mass of adoption here to take off and then generate real-world pro's and con's based on experience. I would value the opinion of German builders where it has been accepted as a viable build method.

 

The manufacturer's promotion of thin-joint is reasonable and logical but I sense they have lost interest from a sales effort/reward perspective. A large segment of self builders like to think different and should be a natural constituency for thin-joint, perhaps the most valuable feedback would be from those who selected ICF or Durisol and might have considered thin-joint during their early self build journey.

 

Two specific unresolved technical points for me arise from that H+H celcon thin-joint video showing an innerskin only-build raising up to gutter height and then the roof being installed. H+H do not clarify if this is based on 100mm, 140mm or wider blocks, the same video also shows something like internal temporary pillar supports being used as the single skin reaches first floor joist height. 

Edited by epsilonGreedy

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Thin joint is a wet system that relies on the mortar “glue” bond for its strength so is only fully structural when the glue is set and all the structural elements including any perpendicular walls are compete for racking strength. TF has the structural strength built into its components as it goes, and the size of these modules means that it is comparatively easy to build a strong structure quickly. 

 

Consider the other key point in that most of the joints in TF are timber to timber and (with the exception of glued floors) have 100% strength immediately after construction. 

 

As @epsilonGreedy says, the European market for this sort of system is reasonably mature but a lot of this is down to the external finishing. Traditional brick in the UK lends itself to the same modular sizing (1 block / 6 bricks) so ties, corners and openings are easy to manage, as is coursing. European finishes such as render on carrier and cladding don’t have the same dependency on the block / brick ratio so this means they have the ability to adopt this method. 

 

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1 hour ago, PeterW said:

Thin joint is a wet system that relies on the mortar “glue” bond for its strength so is only fully structural when the glue is set and all the structural elements including any perpendicular walls are compete for racking strength.

 

 

The proponents of thin-joint concede that with a stop watch running their system does not quite match the remarkable onsite erection times of TF, however it is claimed that once TF design and manufacturing production scheduling at the factory is factored in thin-joint can be faster. I have not read the thin-joint material for a few weeks but I think the mortar is structurally sound within hours.

 

1 hour ago, PeterW said:

Traditional brick in the UK lends itself to the same modular sizing (1 block / 6 bricks) so ties, corners and openings are easy to manage, as is coursing.

 

 

The drilled in wall ties overcome one item in the list but I cannot judge the significance of the other gotchas except to say that with an expensive band saw on site the blocks are easy to shape.

 

The uber free market capitalist lurking in me believes the market is right and there is a good reason the system has not taken off in the UK but I am still searching for the killer point.

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1 hour ago, epsilonGreedy said:

The uber free market capitalist lurking in me believes the market is right and there is a good reason the system has not taken off in the UK but I am still searching for the killer point.

 

Its probably cost. 

 

A thin joint system requires extras such as dual lintels and specialist ties along with secondary processes to put in joist hangers with a precision that needs skill. If you add £1k per unit into a large development then it probably outweighs the benefits as the cost of the shell is probably no more than £20k. 

 

 

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7 hours ago, epsilonGreedy said:

Two specific unresolved technical points for me arise from that H+H celcon thin-joint video showing an innerskin only-build raising up to gutter height and then the roof being installed

if you're referring to the youtube video which mentions the I-house system using panels, then i've spoken to the technical team at H+H and they said, much like doing it with their 620 sized blocks, it can be done with 100 mm wid units

 

4 hours ago, PeterW said:

the cost of the shell is probably no more than £20k

what example came to mind when you said this, did you have a particular sized house in mind and were you referring to the cost of a timber frame in that instance

 

 

Another thought was thermal performance and internal sound and comfort. seems like much of a muchness. Thoughts?

 

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Also in respect of thermal performance and stability, would you gain anything (coat aside) if you had 200 mm lower walls, 100mm upper, and joists ends then obviously completed surrounded

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7 hours ago, Big Neil said:

what example came to mind when you said this, did you have a particular sized house in mind and were you referring to the cost of a timber frame in that instance

 

8x8m brick and block 2 storey detached with single spanning structural internal ground floor wall. So approx 120sqm of brick, 140sqm block. With a brick at £450/Thou and a standard 3.5N block that should be easily from founds to wall plate for £20k. 

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7 hours ago, Big Neil said:

Also in respect of thermal performance and stability, would you gain anything (coat aside) if you had 200 mm lower walls, 100mm upper, and joists ends then obviously completed surrounded

 

Nothing really gained on the thermal performance front with enclosed ends on joists as it’s air infiltration that is the issue. The “Tony Tray” sorts this, as does the use of hangers. 

 

Long decrement delay insulation is keynto stability of temperature. 

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5 minutes ago, PeterW said:

8x8m brick and block 2 storey detached with single spanning structural internal ground floor wall. So approx 120sqm of brick, 140sqm block. With a brick at £450/Thou and a standard 3.5N block that should be easily from founds to wall plate for £20k.

 

And to be clear this includes all materials AND Labour yes? Also would you say that is roughly scalable, so double the areas mentioned thus double the costs?

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Materials and Labour yes - scalable to an extent ...

 

You need a price per square metre of wall to work from and then work up to a laid price for estimating. 

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