Ben100

Stick build or factory built TF

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1 hour ago, Russell griffiths said:

The other was to borrow a mates barn and build up a load of Larson truss panels

If it's load bearing (e.g., propping up the roof) it's not a Larsen truss. A similar truss system which is load bearing might well be a good idea, though.

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46 minutes ago, Ed Davies said:

If it's load bearing (e.g., propping up the roof) it's not a Larsen truss. A similar truss system which is load bearing might well be a good idea, though.

 

As I understand it, John Larsen was comfortable with his original external ladder frame EWI idea being adapted to the twin ladder frame structural truss system for new builds and retaining his name.  Our build uses a twin stud system that is, to all intents and purposes, identical in concept, and has been widely used in North American timber framed homes for a couple of decades now. 

 

John Larsen wanted to come up with a way of better insulating existing homes with an added a non-structural outer frame as a way of making a space that could be filled with non-sheet insulation, whilst retaining the inner stud frame members as the structural components.  Twin stud walls for new builds just takes John Larsen's idea and applies it to a new frame, with the outer stud being the non-structural member (as in John Larsen's add-on frames) and the inner timber being the only structural timber (just as the original timber frame timbers would be in John Larsen's add-on system).

 

In our case the inner stud bears on the concrete slab, whilst the outer stud rests on the 200mm thick EPS upstand around the slab, so isn't load bearing.  In terms of the core principal that John Larsen came up with, which was to virtually remove thermal bridging between the internal structural frame and the external weather cladding support, then there is no difference between the new build twin stud wall and a retrofit ladder frame filled with insulation to hold new cladding.

 

 

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This article, which includes an interview with John Larsen, is pretty clear on the subject: https://www.greenbuildingadvisor.com/article/all-about-larsen-trusses . Similarly, this one (http://www.suncertifiedbuilders.com/en/Larson Truss) even suggests that it should strictly be external to the sheathing of the structural wall.

 

Whatever, I think it'd be better to keep the name specifically for non-structural trusses and call, as that first article does, a structural version a wall truss.

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On 07/11/2018 at 08:59, PeterStarck said:

Yes my frame is a timber I-beam portal frame and was cut and joined in the factory except for the largest frames which were made in two halves in the factory and joined on site. These largest ones were actually erected by hand and the smaller ones lifted in by crane. This picture shows one of the first being lifted in by crane.

 

PA130012.thumb.JPG.9649708ddfb3132224693a241f3f127f.JPG

 

Was there much difference in cost between i-joists and standard structural grade timber?

 

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4 hours ago, Ben100 said:

 

Was there much difference in cost between i-joists and standard structural grade timber?

 

I'm afraid I don't know because we wanted that type of construction because it minimises thermal bridging and it was within our budget for the frame.

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At the moment I am having quotes for my roof 

220mm I joists the prices are on average double the cost of a standard 225x50 structural grade timber. 

 

But its not just the cost of the timber to look into

if you stick build it in normal timber you may use something that could be anything from 140mm to 180mm any bigger and your getting silly, so you need to look at how much insulation you can get in between the joists. 

Not enough. 

So now you need to look at insulation across the face of the studs either inside or outside, so more work and more cost.

a lot to think about not just the cost of the joists. 

Im not clever enough to start talking about u values and all that junk, I just like knocking it all together, I will let somebody else tell you how to get it up to spec with regards insulation. 

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On 13/11/2018 at 18:31, Square Feet said:

I was watching some old episodes of Building the Dream the other night and one had a guy who built his own panels on site.  It is Series 4 episode 1 (Newcastle) if you are interested:

https://www.channel4.com/programmes/building-the-dream/on-demand/57257-012

 

Strange I watched that on Tuesday as well 😲

 

Working my way through all the series.

 

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12 minutes ago, Ben100 said:

 

I will, cheers!

 

Try not to get too irritated by the Wickes ads ;)

 

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