shiplap clad lean to building

[Boatfixer]

I'm in the process of putting up a lean to building to be used as a utility room. The walls are 4x2 studding and I was planning on (from inside to outside) plasterboard, stud wall filled with rockwool insulation, polythene vapour barrier, 2x1 to provide an air gap and shiplap on the outside. I'm now wondering if I should use ply or osb instead of the polythene sheeting to provide more rigidity as well as a vapour barrier or if I should be doing something else entirely..... I Have the studding up and the shiplap treated ready to go so I cant completely change things but now is the last chance to make any design changes.......

 

[MikeG.]

Stop!!!!

Vapour barriers MUST go on the warm side of the insulation. Don't whatever you do, put polythene outside the studs.

Your best bet is to put the OSB on the inside of the studs, Tyvek-type breathable timber-frame membrane around the outside of the studs to retain the insulation, then an inch battened-out cavity then your feather-edge board. Don't forget your insect mesh to prevent insects and vermin getting in behind the FE board.

OSB is so moisture resitant that it will act nicely as a vapour barrier in most circumstances........but for a wet room like a utility I would recommend that you either use a polythene sheet or use foil-backed plasterboard inside the OSB.

OSB makes a nice backing board for plasterboard, and not only gives the wall a solid feel, but also acts as a nice way of allowing fixings to the wall.

Don't forget your extractor fan!

If you want to have your sheathing on the outside of the wall construction, you will need to buy a specialist board such as Panelvent (Excel Industries) which is less vapour resitant than any other boarding.

Isn't Building Control interested in this extension? They should be asking for U value calculations and dew point analysis......and I can tell you right now that 100mm of Rockwool will not be compliant with Part L of the Building regs. I'm a bit worried by this.........

Mike

 

[Escudo]

Mike, I am interested in your advice here.

What is your ideal "wall sandwich" particularly with shed / workshop construction in mind? Inside to out.

What about consideration for sound proofing as well?

I know from previous posts your keen on a course or two of bricks on which to sit a timber frame building. What size timber do you prefer, and how do you go about fixing the timber frame to the bricks?

I am making some plans for a new workshop, giving matters some thought and these are important considerations.

Thanks Mike, cheers, Tony.

 

[wizer]

Time to write a book Mike....

 

[MikeG.]

Time to write a book Mike....

Thanks Tom!!! Yet another job I may never quite get around to.........

Tony,

for a workshop I suggest 4x2 studwork on a DPC on a 2 or 3 brick-high plinth, with a MS strap set in the concrete inside the line of the bricks at about 2m centres (and each side of door openings). This strap can be folded over the timber plate, or run up the stud, depending on their location.

The inside of the studs (and the underside of the ceiling joists, incidentally) can be lined with 11mm OSB, painted white.

Fully fill the studs with insulation.......if you are earning a livng out there and are in it all day every day, then I would suggest Kingspan, but for weekend woodworkers then 100mm mineral wool ("Rockwool" or similar), with cheapo building paper over the outside of the studs to hold the insulation up.

Then I suggest a 25mm battened zone with either boards or render on EML (and another layer of building paper behind the eml to give the renderer a backing to push up to). Don't forget to insect proof this battened zone.

This is for workshops only!!! I wouldn't want anyone to think that this was suitable for houses/ extensions.........such as the original poster has done!

I'm always happy to help with a sketch or two, Tony.....just let me know.

Mike

 

[Boatfixer]

Thanks Mike for your invaluable advise as always - I did have a nagging doubt that something was wrong with my cunning plan hence asking the question here before I got too far. A quick trip to the builders merchant and a roll of breathable membrane is in place of the plastic.

I think I was over ambitious in describing this as a utility room though - it isn't attached to the house at all. It replaces the tumbledown coal shed and loo at the back of the yard in which our washing machine has been rusting for the past couple of years (the kitchen in this house is tiny...). It is supported on two sides by the yard brick walls and is more an over-engineered shed! It will now be large enough for a washing machine and a tumble dryer but you wouldn't want to swing a cat in it!

Now the next question - anyone got any top tips on attaching shiplap? I assume you will need some scope for expansion and contraction (I have already stained it before fitting) but how much per plank should I allow? Also I was planning on using stainless steel ring shank nails - or is there something better?

The only other thing I need to find is a supplier of insect mesh - anyone got any ideas?

 

[Escudo]

Yes - thanks Mike for your advice and wisdom on these important matters.

Like boat it is good to get this right first time.

cheers, Tony

 

[mahking51]

Hi Mike,
Would love to see a sketch please!
Also, OSB?
Why the battened air space?
I was thinking of using the T&G particle board type flooring material on the inside as it gives a good supprt for shelves etc; good/bad idea?
Martin
(Avidly watching this to avoid asking you twice!! )

 

[CWatters]

Just for info - the board on the inside is partly to stop racking of the structure in high winds.

If the structure is bigger than 15sqm then keep it >1m from the site boundary or Building Control Approval is required...and they may have an issue with flamability of a timber structure.

 

[MikeG.]

Now the next question - anyone got any top tips on attaching shiplap? I assume you will need some scope for expansion and contraction (I have already stained it before fitting) but how much per plank should I allow?

The only other thing I need to find is a supplier of insect mesh - anyone got any ideas?

Different terms mean different things in different parts of the country........by shiplap, do you mean feather-edged board? This is a sawn board which is made by slicing a normal rectilinear board on the diagonal (not quite corner to corner) in section.

If so, the correct way to fix is to overlap by 25mm per course/ board, and to use one nail per board per stud position 30mm up from the bottom edge. This means the nail will miss the top of the overlapped board by 5mm, but will trap it by nailing the board over. This cleverly allows for movement but retains both edges of the boards. Don't hit the nail home too hard or you will bend the board, and try and avoid using a nail gun.

Mesh is commonly supplied at all Builder's Merchants.

Mike

 

[MikeG.]

Hi Mike,
Would love to see a sketch please!
Also, OSB?
Why the battened air space?
I was thinking of using the T&G particle board type flooring material on the inside as it gives a good supprt for shelves etc; good/bad idea?
Martin

Martin,

I won't post a sketch because inevitably someone will take it out of context and use it for a building or part of a building for which it isn't appropriate. I'll do sketches by PM for specific cases.

OSB is a cheap sheathing board, for windbracing, stiffening up structure, and as a handy backer for plasterboard to avoid the cheap hollow-sounding wall effect that you can get with timber frame if you aren't careful.

The external battened air-space allows for moisture penetration through the boards or render, which is inevitable. The air movement in this vented space allows it to dry off without doing any harm........but continuous air-paths are important.

Before I comment on your inner lining.........what sort of building are we talking about/ Is it a workshop?

Mike

 

[CWatters]

Now the next question - anyone got any top tips on attaching shiplap? ?

See..
http://www.vastern.co.uk/tc-fixing-feather.html
and perhaps..
http://www.nail-it.co.uk/

The only other thing I need to find is a supplier of insect mesh - anyone got any ideas?

I thought Screwfix had it but all I can see are Eaves Combs....
http://www.screwfix.com/prods/40157/Bui ... ES-_-40157

 

[Boatfixer]

Thanks Colin - that link was just the thing I was thinking of. Now on a search for Insect mesh. My local independent builder merchant has none and Wickes is as to be expected..... I can see another half day being wasted . This thing is taking far too long and we are running out of clean clothes! I can see the washing machine being set up in the yard if it stays sunny!

 

[MikeG.]

A great insect mesh is the stainless steel plasterer's angle bead (thin coat), which will insect proof a 25mm gap (perfect for the situation I described in an earlier post).

Mike

 

[bluezephyr]

http://www.flydor.co.uk/com_mesh.html

Is this Mesh anygood? My workshop happens to be beside the guys who cut out strips for this company :wink:

 

[Boatfixer]

OK - another daft question (I know the only daft questions are the ones you don't ask but I'm more used to building things as light as possible - this thing would sink!) What thickness OSB under the plasterboard? I'm trying not to lose any space but would 18 mm be better than say 11 mm or even 6 mm?

Thanks
Graham

 

[MikeG.]

I think 11 is about ideal.......the thick stuff is just soooooooo heavy, and the 6mm stuff probably isn't up to the job. You could use ply, but be careful which one you pick if you do go this route, as some are just rubbish.

Mike