Patrick

I-Beam/I-Joist First Floor hanging Air tightness

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Posted (edited)

Could not find these details anywhere so far.

Very often the Stick Build Constructions are  traditional Framing techniques, where the first floor Joist sit on top of the Groundfloor studs and so on...

 

For a Portal Frame construction, people seem to use prefab timber frame companies.So the company will sort out these details.

 

I wanted to see if someone has experience in this or how you would do it/ are doing it.

I was wondering what would be the best way to attach the first floor Joists to the outside Walls in a Portal Frame, while  keeping the Airbarrier flowing without interruption.

I hijacked one of your picture @PeterStarck to demonstrate what I meanPA120006.thumb.JPG.d258c7b1f9b150776d2ec02d709356be.JPG

Here are the first floor joists, attached to the outer frame without any airbarrier (as far a i can see) .

This means, as far as I understand, that you later have to work/tape around each Joist for airtightness.

 

 

I have Found one solution that made sense to me, but I am not sure if that  works well :

 

Studs are carved in on the level of the floor (potential problem with the I-Joists)

928660359_Screenshot2019-02-10at21_22_05.png.f0be271ab2746ab86c998dd595663df3.png

 

 

than timber studs are inserted as a backing board 1275073998_Screenshot2019-02-10at21_11_03.png.ac3298a167575a81912eebd5f46a629f.png

 

 

before the Airtight Membrane OSB (in this example just plain OSB) is Nailed on to the front . Than joist hangers are Nailed into the timber studs(through the OSB)

1783706316_Screenshot2019-02-10at21_10_35.png.1c4ecfcc87c4e4fe43e546511e28fa74.png

And the Floor Joists go into the Joist hangers.

 

Later on the Osb in the Groundfloor and the OSB in the top floor can be taped to the osb section "behind" the floorjoists/

Seems like a method of eliminating some problems(cold bridging, airtightness) 

 

It than looks a bit like this:

347422941_Floorjoisthangers.thumb.jpg.dbcdba0e73c3534d12328c5c81ea940a.jpg

 

Hope this all makes sense. I m much better with visualising things  with plans/photos so if anybody got some sections or drawings of a similar setup that works, I would be very greatful .

All Ideas are welcome.

Edited by Patrick
Forgot something

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I would wait for people to confirm what I’m thinking, but I think you need aTONY TRAY. 

i havnt looked into it much but I’m thinking of doing something similar with my roof

 

you basically get a strip say 600-750mm wide of your chosen air tight membrane and install this first horizontally around the building at the floor height, you then install all your hard ware and joists onto this leaving a flap hanging down below ceiling level and one poking up above first floor level,

you then tape your other membranes to this strip as you finish your build. 

 

Im sure someone will have a sketch. 

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Our TF had a craned-in floor cassette, and each portion came with a factory-fitted strip of heavy polythene around the perimeter to act as a Tony Tray.

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Sorry I do not have a sketch or any form of visuals but we had a Tony tray as such with our timber frame. Our frame was a fully built cassette with insulation and vapour membrane already built in when the frame arrived. When the ground floor panels had been erected the timber frame crew laid an airtightness membrane horizontally along the top of these panels and then folded this onto the floor cassette when this was put on top of the lower panels. The upper panels had a loose/dangly piece of membrane that when the upper panel was put in place the loose membrane was then fixed down and taped onto the lower panels thus ensuring a very complete wrap. We had our air test done in January and we acheived 0.56ACH and that was with a large leak on the Internorm sliding doors.

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9 hours ago, Patrick said:

I wanted to see if someone has experience in this or how you would do it/ are doing it.

I was wondering what would be the best way to attach the first floor Joists to the outside Walls in a Portal Frame, while  keeping the Airbarrier flowing without interruption.

I hijacked one of your picture @PeterStarck to demonstrate what I mean

Our first floor metal web joists hang from a ledger plate that is attached to the I-beam wall studs. We used 300mm I-beams and extended them to 350mm by adding battens to the inner flanges of the i-beams. The ledger plate is the same thickness as the battens and sits on those battens and is nailed to the I-beam flanges. We don't have any membranes or tapes in our construction as the wall itself with the Icynene insulation is the airtightness layer. We achieved an airtightness result of 0.47ACH.

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1 hour ago, Cambs said:

Here’s a link to a sketch of the Tony Tray

 

http://tonyshouse.readinguk.org/tonytray.pdf

Thanks.

This than only leaves me with the question how to attach it to the I-Beam wall in a similar fashion than @PeterStarck done it . His method seems to be excellent, even though i would like to do the same while still using Blown in Cellulose . So need to put a Foil behind the ledger plate. Tricky .

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Just Found this one :

 

Seems reasonable , if you would put Passivplus OSB on the walls,taped, that is Airtightness sorted. Apart from the piercings through the OSB with Bolts/screws.

Or is this a problem? I m not sure about weight capacity of OSB if you hang your floor from it.it is bolted to the frame, but still .

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3 hours ago, Patrick said:

Thanks.

This than only leaves me with the question how to attach it to the I-Beam wall in a similar fashion than @PeterStarck done it . His method seems to be excellent, even though i would like to do the same while still using Blown in Cellulose . So need to put a Foil behind the ledger plate. Tricky .

If you attach a wide strip of membrane to the I-beams behind the ledger plate before fitting the ledger plate you can tape the membrane to that strip on the first floor and on the ground floor.

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thats probably the best way to go, although your comment made me think and I am looking into spray foam now. I always thought it is too expensive, but seems quite ok pricewise.

How happy are you with it? My only concern would toxicity of the foam.

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1 hour ago, Patrick said:

thats probably the best way to go, although your comment made me think and I am looking into spray foam now. I always thought it is too expensive, but seems quite ok pricewise.

How happy are you with it? My only concern would toxicity of the foam.

There are different types of spray foam. I can only really comment on Icynene which although we had to do a lot of trimming, worked well for us. It is sprayed on very thinly and expands IIRC about 100 times so layers of around 100mm are built up. It sets into a rubbery flexible foam that off-gases quickly and after a couple of days there was no smell. The only disadvantage I have heard about is that it doesn't stick very well to a cold surface so it's not a job for a cold winter.

 

Icynene BBA.pdf

Icynene Spec.pdf

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alternatively put the air tight layer on the outside - egger dhf, blown cellulose and osb inside with vcl layer if not using something like smartply.

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