Vapour barrier for workshop

[Redhill Red]

HI all,

I am soon to start building a workshop (6m X 5m) in my garden and at the moment I am in the planning stage (lots of reading and looking at pictures in the excellant workshop build threads).

One initial query I have is concerning the use of vapour barrier cloth/sheeting, some put it on the outside of the insulation next to the cladding others on the inside of the insulation, and I noticed one builder(Carlsberg i think ?) put some on both the inside and the outside.

I was hoping someone could explain the theory of each method or should I go belt & braces and do both ?.

Also a cheeky favour to ask, if there is anyone in the Nottinghamsire/east midlands area who is willing to let me look at their build project to see/pick their brains it would be much appreciated because at the moment my head is buzzing with design ideas and potential build problems, materials to use etc etc.

 

[OLD]

People in a building produce water vapour (w/v), insulation can over time be saturated by this also wood and water don't live well together.
Wall construction should be inner lining ,continuous vapour barrier (v/b),insulation ,breathable membrane (b/m),a gap ,outer cladding.
The w/v is stopped by the v/b keeping insulation good the b/m allows any w/v in structure due to drying out or changes in humidity to pass through in to the gap so it does not wet the back of the cladding and is dissipated into the out side air.
These are the principals ,design will vary slightly for different materials .

 

[tnimble]

I can't add anything to that.

 

[9fingers]

Near square dimension as you suggest is ideal for flexibility of the final workspace. As you add machines you will be bound to want to re-organise.

However a span of 5 or 6 metres will need careful roof design to make sure that the roof is not too heavy or too flimsy. The worst load is snow. 1 foot of snow = 1" water which will weigh about 3/4 tonne. Obviously all the weight is carried by the walls and you will need to make sure they stay vertical under load without the bracing getting in the way.

Concrete block walls with piers every couple of metres will be very stable.

Also 30 sq metres is the maximum size before building regulations will apply. Also, if the structure is within 1 metre of the boundary, in order to stay exempt from BR between 15 and 30 sqm it needs to have good fire resistance.

If you are ever down Southampton way then let me know and I can give you a guided tour of my workshop.

Bob

 

[Redhill Red]

Thank you all for your replies,

Thanks Old for the good explanation of the two different kinds of barrier and I think i will go with using both . After the breathable membrane goes on the outside of the frame i will probably put a strip of 2"x 1" pressure treated onto each upright to fix the cladding to therefore keeping a small air gap as you suggest to keep water off the inside of the cladding.

I too 9fingers have slight reservations concerning the size and am I probably looking to make it too big, I have been thinking of probably going with a size of 6m x 4m, although I would like to make it as big as possible due to after several years of working in a single garage if I am going to the expense of building a new workshop I don't want to end up disappointed.

 

[mailee]

Hi Redhill, I have built my own workshop and it is 23' X 13' and it looks like a summer house. I did make up plans for it after I built it?? but if you are interested then there is a direct link to it on a site called readers sheds which can be found in the other topics forum of this site. I wouldn't be unhappy if you decided to vote for it too as it is in the running for shed of the year. It has also been published in Good woodworking magazine earlier this year. The workshop is fully insulated and double glazed and the whole thing was built from scratch even the doors and windows. If you need any further help please feel free to ask, it's what we are here for. Hope this is of some help to you. Oh and by the way on the readers shed site there is a full write up of the build in a diary form. :wink:

 

[SammyQ]

"on a site called readers sheds which can be found in the other topics forum of this site."

Wherzat???

 

[Woodmagnet]

Sammie, try General Chat/vote for me. You'll find it there. :wink:

 

[SammyQ]

Cheers! found it right away....Gawd, my pit looks nowt like these places. Must post summat and give them a laugh.