Steel RSJ to Oak Purlins..how to join on 100m bearing?

[TimG]

Hi All,

 

First of all thankyou for your time in reading this.

Our current new build design has two parrelel 178x102x19 steel RSJ purlins running width of building made up of a 3.45m and 6.6m section (two of each) The two beams were to be bolted together.

The ceiling are vaulted, so Purlins will be visible. Structural engineer has suggsted we can use 200x150 oak Purlins (air or kiln dried to reduce chance of later movment). Sourcing 6.6m Oak purlins is very diificult so it will be seperated into 2 lengths of 3.3m. This potetially means 6 scarf (or similar) joints! Are they suitable for a 100m bearing on concrete padstone or will they most likely require bolting (fished joint)?

I have thought about cladding the steel after, but if I can use a natural materials in the first place then I would like to do that. Any comments/suggestions appreciated (located E of Basinsgtoke, Hampshire)

[tonyshouse]

Trees grow a lot taller than 6.6m! Try a local sawmill 

[Gus Potter]

Yes, not easy to source and anything reclaimed at that length and virgin timber requires a bit more thought, may be a bit more bashed about than you want. I would consider the over cladding once you have got all the dusty and wet trades out the way.

 

You may have an oak stair which will have a more "Engineered" look?  In the UK we tend to initially think about "solid timber" beams, stairs and so on. In the US and Canada they often rough stuff out then over clad in a higher quality timber. Over cladding can often simplify the structural issues so you get to spend more on the things you see?

Edited March 1, 2021 by Gus Potter
extra thought

[Temp]

I got a 6.5 m green oak beam from my local sawmill no problem. Not sure if you can get dried oak that big though.

 

4 hours ago, TimG said:

Sourcing 6.6m Oak purlins is very diificult so it will be seperated into 2 lengths of 3.3m. This potetially means 6 scarf (or similar) joints!

 

Just remember each bit must be longer than 3.3m.

 

https://youtu.be/-SUtoKKNKHQ

[Temp]

This place is offering air dried upto 7m..

https://www.iwood.co.uk/beams/32/oak-european/

[Conor]

Glulam seems to be an obvious alternative. Can be made to your exact spec and can look good (if it's your kind of thing).

[Russell griffiths]

Who said 100mm bearing, that is small and most end bearings these days have been increased. 

 

[Temp]

6 hours ago, Russell griffiths said:

Who said 100mm bearing, that is small and most end bearings these days have been increased. 

 

 

My guess is that's the width of the wall so the bearing will actually be 150x100 onto a padstone.

[TimG]

Thankyou soo much for all taking the time to reply. I've decided to use the steels as purlins and cladd in faux oak/oak boards after, they are in the vaulted ceiling so not under close inspection! The oak beans were proving too expensive and too much of a headache!

100mm is from BR drawings...yes correct re padstone...will be sitting on thermalite walls (still amazes me how much weight can go on a thermalite wall!)

[connick159]

On 03/03/2021 at 11:45, TimG said:

Thankyou soo much for all taking the time to reply. I've decided to use the steels as purlins and cladd in faux oak/oak boards after, they are in the vaulted ceiling so not under close inspection! The oak beans were proving too expensive and too much of a headache!

100mm is from BR drawings...yes correct re padstone...will be sitting on thermalite walls (still amazes me how much weight can go on a thermalite wall!)

interested to see if you've found any good sources for cladding the steel beams. I'm looking to do the exact same thing.

 

Also. will you be installing all the plasterboard first and then cladding the beam or cladding first and then installing the cladding?

 

Thanks