26x16 Garden cabin advice

[Bretttf]

Hi guys. I'm new on here after lurking & researching & admiring for a while. I'm English living in England & I love the American log cabins. Apologies now as I suspect there will be questions!
I'm a maintenance engineer so I'm handy but Im struggling to progress & make decisions due my perfectionist nature!
Anyway, an opportunity has arose for me to build a flat, sloping roof front to back cabin/fun room for me & my 3 sons.
A friend of mine has kindly given me enough 4x3 to complete all the framing.
Another friend of mine has offered my endless supply of 4x1 in approx. 36" lengths.
Would the 4x1 be ok to sheath my frame inside and out? Floor and ceiling aswell?
I had thought about water proofing it all prior to fitting with and engine oil & parafin mix.
I plan to house wrap/tyvek the exterior over the sheathing. include floor & roof before felt?
I have a problem here that I'd also like help with. The 2 sides & back will have very limited access once in place. What would be a virtually maintenance free weatherproof coating/material.
I plan to use 6x2 for floor and ceiling joists.
From the interior going out I plan to have interior ply (again free 36"x36" x3/4" sheets) then plastic sheet vapour barrier, fibre glass insulation, the 4x1 strips, house wrap then loglap on the front and whateverbis suggested for the 2 sides & the back.

[rocking23nf]

2x6 joists are really tiny for floor joists, I would go 2x8 or 2x10.

And I would rethink using 4x1 for sheathing, thats alot of work. 4x8 sheets go on easy, and are made for 16' on center framing.

I mean its hard to turn down free matieral, but the time spent using 3x3's and 4x1's would be insane.

Also walls are usually 2x6 or 2x4 in some area, 2x6 is the norm around here.

[Bretttf]

2x6 joists are really tiny for floor joists, I would go 2x8 or 2x10.

And I would rethink using 4x1 for sheathing, thats alot of work. 4x8 sheets go on easy, and are made for 16' on center framing.

I mean its hard to turn down free matieral, but the time spent using 3x3's and 4x1's would be insane.

Also walls are usually 2x6 or 2x4 in some area, 2x6 is the norm around here.

Thanks for the quick response.
I know what you mean by the work involved however The 4x1 are assembled in 36" square boards held together with 3 4x1 cross pieces. They are used to protect paper on top of pallets/skids. So they would go on easier than single 4x1 strips. I have a access to a Paslode nail gun so that'll save me time too.
The 3 x3 is 3' square ply sheets at 3/4 thick.
The free materials are all metric, the sizes I'm giving are nearest Imperial. Luckily my dad taught me the old Imperial system too!
I think I will upgrade the joists to at least 8".
Would that be the same for the flat roof?

[Bretttf]

Any other ideas or opinions please guys?

[glenn kangiser]

I would go to felt rather than Tyvek as you will likely have lots of penetrations and if Tyvek gets a leak then water gets in but not out and that causes rot.  Felt will wick water out.  Maintenence free... Possibly no finish at all if your wood is exposed.  There are 150 year old houses around here with exposed wood sides.  Just be sure the wood can drain.. possibly set it out on vertical strips to provide a drainage plane.

Sounds like it could be interesting.

Possibly a center beam if you want to use 2x6 floor joists.  I didn't calc it.

[Bretttf]

Thank you Glenn.
I hadn't considered the water trap on fitting my sheeting boards with the 4x1 horizontal. I will fit with the vertical.
Is my plan from the inside out ok? And rather than Tyvek just leave a heavy duty roofing type felt wrapped all round the sides?

The back and sides would stay like that but the front I plan to loglap or shiplap or similar for improved appearance. The back and sides are out of view so the felt finish would be acceptable.
Would treating my panels with oil & parafin mix be ok or would that prevent the moisture movement/venting?

And yes, interesting is one word for it! Mind boggling is another! I have got great motivation and drive from reading all the projects on here and also ideas and inspiration.
If this project goes ok the skills I learn from it may be put to use building one of those Tiny Houses on a trailor. Me and my 3 boys camp a few times a year and we dont ever recall seeing anything like it in England.

[Bretttf]

Just a thought I had when a centre support beam was mentioned. In clearing out my old workshop I have found 3 pairs of 3 ton car axle stands.
Would these be ok to help support my centre beam?
They would be sat on a concrete block or 2 & on a flattened bed of gravel.
I would secure in place with wraps of stainless steel builders banding or some other brackets.