I built my shed 3 years ago from 3x2", 24" on center stud. 18mm ply on outside painted with fence paint (needs another coat this summer)12mm on inside with Knauf-insulation. On air gap, on plastic, I've had one stain come through below one of the windows, also some light mould behind a wooden jig i hung on that same wall. the jig might have been damp and perhaps too close to the wall for air circulation. the mould seems not ot have come back but still slightly worrid. there is one sheet of ply I woulden't mind replacing. What do you think?
pity the ply thicknesses weren't the other way around! The rule is to have a greater moisture resistance on the inside than the outside.........5 times greater in the case of a house.
Knauf make a million types of insulation. I hope you have a soft mineral-wool type product rather than a stiff board.
I am sure you will eventually get problems with this construction......but ventilation is the key. Make sure there is loads of ventilation to the inside of the shed.
If there is one piece of ply you want to replace, this would be a good chance to have a look inside the wall and see if there is any sign of damp. Choose a really cold damp morning and run your hand along the inner fface of both sheets of ply. Any dampness at all and you will have problems.
In the long run, I would batten out the outside and clad with feather-edge board...... and possibly drill a series of 1" holes around the ply both inside and outside the shed, top and bottom if you suspect that there is any moisture between the inner and outer ply sheets. On the outside, cover all with a timber-frame membrane (Tyvek or equivalent) before battening.
Mould can be a real health hazard...the spores can make you quite ill, and people are getting sued a lot in the States over mould in houses. You must take notice if you see mould......and ventilation is the key.
Hi Mike , sorry if my username offends , but it was a nicname given to me when I first started on site , has stuck ever since , and that is a long time , and it bears no relevation to colour or creed , my real name is Sam .
As for the " no building material sweats " is true as far as the material goes , but if you have a timber cladding system it will never be air tight no matter how well you force the joints together , and as soon as the air moisture content rises you will find it's way in and as soon as it finds a barrier of a different temperature it will condensate , and will at some point evaporate again , but in the mean time it will lay against this surface .basicaly it will find its way into the stud stucture by means of air gaps or poorly maintained cladding that will act like a sponge and track through , once in the cavity it will condensate against the insulation and the studs , this then lays there and when the temperature rises again it will condensate ( sweat ) . Yes the ideal material to use would eb a breathable moisture barrier or heavy duty polythene barrier but that can only be done if you have not fitted the cladding yet .
As for the cavity yes , idealy you want the cavity on the outer side of the cavity , but ever tried retroffiting it that way ! And the void you will create by pushing the insulation to the outer side will act as part of the sound muffling system along with the rockwall , it works by bouncing the sound from the internal skin against the mineral insulation and therefore dampning the sound , there are always the ideal ways to fit a system but sometmes you have to compromise certain elements of it because you have to fit a retro fit system .
I run a very successful building company and my brother inlaw runs a very successful damp and wood rot treatment company , both of which have strict codes of practice to adhere and forever changing standards and methods , we work together on many projects and it is suprising the methods that are specified by architects and Building control / inspectors to get over these problems .
As for the question of the moisture created by heating a shed in the winter .....Even though you are trying to heat it you should still have suffiecient ventilation at all times , even if you dont want to loose heat , but that should allow for any moisture inside the building to escape .
I'll strip out the one side this summer (Ha Ha) and look for sines of water staining and let it dry out if necessary. I like the ideas of the feather-edge board very much and vapour barriers the way to go. I don't want to add to the thickness of the wall if i can help it. Thanks again.
Try using a breathable roofing membrane ie tyvek , klobber ect , fit it to the studs using felt nails or a heavy duty stapler , you only need enough fixings to hold it in place til the boards are fitted , needs to tight enough to not leave any flex in it , when fixing the F/E boards ( horizontaly ) you need to allow 25 mm overlap per board , and only one fixing per boards per stud , in the thicker side which will be at the bottom and overlapping the previous board , to many fixings will aid its splitting when it moves between the warm dry seasons and wet winter seasons . the breathable roofing membrane isnt cheap so it might be worth trying to blag a part roll from a roofer near you and allow atleast 150 mm overlap on it unlessit has a minimum overlap marked on it .
The above is spot-on.......although I would add that battening out above the Tyvek would be best as it would give the back of the boards a chance to dry out properly, as well as the outside of the membrane,
Additionally, do stain your boards before you nails them in place. As they shrink they reveal a stripe of raw timber if you do it once you have finished.
The single nail should pass through the outer (upper) board, and not the lower board. This will still trap the top edge of the lower board each time, but allow it to shrink without splitting. About 30mm up from the bottom edge of each board is about right.
Sorry for not mentioning the battening it out , but was just going by the fact that PJ mentioned he didnt want to expand the size to greatly , could use as little as 10mm batten , which would still do the job aswell .Try using a copper or alu fixing to as they will last longer than a BZP nail as when they start to rust it will leach a red rust stain on to the wood .
Thank again Guys, it just so happens I do have some roofing baton that i could rip down. Looking at the shed again it does look as if it is only the one sheet of ply that has failed. But i will take a better at look at the inside in the summer and decide then. Thats another job to add to my TO DO LIST.
If you make your own double glazing make the panels NOT parallel by about 10 degrees, and line the end with the widest gap with sound absorbent material. The sound will get reflected into this rather than being bounced backwards and forwards between the glass untill it get through!
Never tried it myself but the theory seems to work and I'm told it makes a difference!
Whilst that sounds a really interesting idea, anybody making their own double glazing is going to have problems with condensation occuring between the glass sheets. This could lead to mould growth. Sealed units usually have an inert gas in them to avoid this danger.
I have a triple glazed unit in my shed window........left over from building the house..... but its the useless doors that let all the sound out and the drafts in.
Condensation need not be a problem. You need a few small ventilation holes top and bottom to the outside, loosley plugged with cotton wool or similar to keep insects out. The air movement is slow and doesn't affect the thermal property, but it ensures the humidity is the same as outside, but the temperature will be above outside so the air in the void will be above dewpoint. It may get there briefly when the temperature ouside falls rapidly but should soon clear.
That is an answer to the condensation problem, certainly (not with cotton wool, though, because that wouldn't let air through when soaked with condensation)...but of course it hugely effects the thermal properties of the glazing. It becomes sheltered single glazing rather than double glazing. If you are going to do-it-yourself in terms of double glazing, better to have the inner leaf framed and hinged so that you can open it for cleaning.
Better still is to grab a sealed double glazed unit out of a skip and use that instead. Or grab 2 and have quadruple glazing....inner unit openable.......that should keep most of the sound and heat in!
Sound waves bend themselves into holes, and the drainage holes would negate most of the benefits of having 2 panes of glass, I reckon, by creating a pathway into the void.
