OB Timber Framed House - How weatherproof does it have to be?

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  1. #1
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    Default OB Timber Framed House - How weatherproof does it have to be?

    I have my owner-built my house to lockup stage and the house is currently being water blasted by ex-cyclone Oswald in Brisbane.

    Although the house is withstanding the high winds well, at some places rain water has seeped past the FC cladding and water vapour sarking and wet the timber frame is some places and in one place, onto the floor.

    Given that no house is built absolutely water-tight, am I being overly concerned with the site of some frame wetness, because it will hopefully dry out when fine weather returns?

    Is this drying a normal cycle to expect - particularly in severe weather - or should no water ever get onto the wood frame???

  2. #2
    4K Club Member ringtail's Avatar
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    In theory no water should ever be able to penetrate to the frame. However, in reality this is rarely the case. With poor construction technique, lack of flashings and poor material selection water often ends up where it is least wanted. Wind driven rain, like we are having now shows up all problem areas. Learn from it and take the required action. In older houses its not a problem as they are hardwood framed and a bit of water does nothing to them. Newer pine framed houses sometimes get completely soaked during construction then finished while still wet, with the obvious issues down the track. I would let it dry completely before boxing it up and after this rain that will mean at least 4 weeks of dry weather. BTW, what sort of FC cladding have you used ?

  3. #3
    cas
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    Where's it coming in? Around the bottom plate, around openings, halfway up the wall, the top? And as ringtail said, what form of FC is it?

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    Quote Originally Posted by ringtail View Post
    BTW, what sort of FC cladding have you used ?
    Thanks for your help.

    The cladding is James Hardie Scyon Stria which is 14mm thick and overlocks each sheet below - however there is a gap where the boards end at external vertical steel I columns - but the water should just run down these gaps .

    Funny, when just the sarking was on it was more weatherproof because of the vertical plane formed which guided the water down. Now that that plane is impeded by the inside of the cladding, water must go through the holes in the sarking onto the frame somewhat.

    I haven't had these problems in the passing storm, just in this prolonged weather event. At least I know the worst, I guess...

    Just the fact that the sarking has breathing holes, must imply that water intrusion into the frame is expected.

    I will seal outside the places as best I can, however, to try and stop the plaster getting wet if/when it happens again in heavy rain events, when I attach the plasterboard to the frame, I'm thinking of attaching some plastic sheeting (or bitumous paint) to the frame in those areas...maybe even wall vents to help dry things up. Any opinion on this strategy?

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    Is OB still in use up there? It has been many many years since I have seen an OB frame down here in Vic.

    Tools

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    Quote Originally Posted by cas View Post
    Where's it coming in? Around the bottom plate, around openings, halfway up the wall, the top?
    In different places, probably a combination of the above. The leaks at the bottom sides of a sliding doors I think is from a small gap in the sealant I used (no more gaps) to seal down between the aluminium frame, the edges of the cladding, and the black flashing which goes behind the cladding. I've got some trim to go around the outside of this door so that might help further, but I will check the sealant thoroughly first.

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    Quote Originally Posted by Tools View Post
    Is OB still in use up there? It has been many many years since I have seen an OB frame down here in Vic.

    Tools
    I'm meaning "owner builder" for OB, what did you mean?

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    Ahh, I see. OB stands for Ordinary Builder's Hardwood. That's what I thought you meant when you referred to it as an OB frame.

    Tools

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    4K Club Member ringtail's Avatar
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    Have you used a flashing system where the cladding meets the steel ? All external sealing should be done with rubberised or urethane type sealant, like sika or similiar. And use plenty of it. A bead of 6 mm ( for example) is useless. It will shrink and crack. 10 mm wide and 10 mm deep should give plenty of flexibility to the caulked joint even if its applied over a foam backing rod.

  10. #10
    JB1
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    Default OB Timber Framed House - How weatherproof does it have to be?

    I would love to use OB hardwood my house frame but wonder if it is straight enough to be used as studs.

    In the current house I'm building, I used OB hardwood for my noggins as suggested by my carpenter. It doesn't split when nailed like pine.

    Next time I build a house I will use KDHW studs and bottom plate for the wet areas.

    I wonder what type of hardwood my 50yo house uses. Looks better than OB but not as good as KD




    Sent from my iPhone 4S using Tapatalk

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    The building should be completely weatherproof in all but the most extreme weather conditions, that would be high winds with driven rain.
    OB timber is not an industry trade term, could be an old local or regional term though

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    As the son of a builder (now 79 and apparently retiring this year), I can vouch for the term OB for house framing before pine took over. Like Tools I I immediately thought of OB framing when I read the title of this thread.


    Danny

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    Quote Originally Posted by Danny.S View Post
    As the son of a builder (now 79 and apparently retiring this year), I can vouch for the term OB for house framing before pine took over. Like Tools I I immediately thought of OB framing when I read the title of this thread.


    Danny
    If you could find a reference to the terminology "OB" in an Australian standard or similar publication that would make me sit up & take notice, as soon as it appeared in the post I was not the only one confused the vernacular term, but then I cant speak for those timber millers in some gully at the back of orbost. 99.9% of the industry knows what RSHWD ( rough sawn hardwood ) is because of standardised training nationwide.
    regards inter

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    4K Club Member ringtail's Avatar
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    For me OB has always meant Owner Builder. Maybe I'm just showing my age, or lack of it

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    We were taught by our pre-app teacher that we may come across the term OB which was ordinary building timber/lumber. It's just an old fashioned term that some may know. Maybe it depends on where you live in the country. It would be rare to hear the term used.

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    Quote Originally Posted by intertd6 View Post
    If you could find a reference to the terminology "OB" in an Australian standard or similar publication that would make me sit up & take notice, as soon as it appeared in the post I was not the only one confused the vernacular term, but then I cant speak for those timber millers in some gully at the back of orbost. 99.9% of the industry knows what RSHWD ( rough sawn hardwood ) is because of standardised training nationwide.
    regards inter
    Nah I can't reference it nor can I find mention on Google (other than comments on this forum), but then again this forum and google didn't exist when OB was being used. Wouldn't there, in any trade, be many common terms used that aren't part of "standardised training"? After all, terms like this were in place well before standardised training and building regs even existed.

    I think it was just a slang term, not used anymore, but hearing it from my dad and two builder brothers all my life makes it real enough for me.

    Anyway apologies to the OP for being way OT talking about OB.

    Danny

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    Quote Originally Posted by danny.s View Post

    anyway apologies to the op for being way ot talking about ob.

    danny
    That's funny

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    I thought OB meant off bench, just another way of saying rough sawn or straight from the saw.

  19. #19
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    Back to the OP who is an OB asking about leaks past the cladding on his new place. There should be no leaks, zero, zilch - ever! Your comment 'given that no house is absolutely watertight' - is right only if not properly designed, built or maintained. If there are leaks in your new place then you have not constructed properly - it seems by not sealing junctions using the correct type or amount of sealant or components.

    The sarking is designed to be breathable ie: permeable to water vapour and that is not water! You will have to make sure all areas get dry as trying to seal while still damp or wet will fail.

    I know it goes against the 'bloke' genes, but read these (again if you have already) http://scyon.com.au/products/downloa...ual+Jan+12.pdf and you will see clear references on how all the possible ways water might intrude are supposed to be sealed. Not too that the sarking is vapour permeable at low or medium levels and water barrier at high level. It even has section on moisture management and the need to take extra precautions where wind driven rain is possible:

    Moisture Management
    It is the responsibility of designer or specifier to identify moisture related risks associated with any particular building design. Wall construction design must effectively manage moisture, accounting for both the interior and exterior environments of the building, particularly in buildings that have a higher risk of wind driven rain penetration or that are artificially heated or cooled.
    In addition, all wall openings, penetrations, junctions, connections, window sills, heads and jambs must incorporate appropriate flashing and waterproofing. Materials, components and their installation that are used to manage moisture in framed wall construction must, at a minimum, comply with the requirements of relevant standards and the BCA.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

  20. #20
    4K Club Member ringtail's Avatar
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    Wind driven raqin is what its all about up here at the moment. 3 days of relentless rain driven by 60 - 100 km/h ENE winds. That sort of wind will make water climb walls and get under laps in boards etc... I went over to a house yesterday that is 8 years old, uses some form of fibre cement board cladding and there was water in the garage. The wind had driven the rain right through. I dont think any cladding system would be 100 % waterproof in the conditions we have just had.

  21. #21
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    Quote Originally Posted by intertd6 View Post
    OB timber is not an industry trade term, could be an old local or regional term though
    It certainly is a trade term here in Vic and has been since before I started my apprenticeship back in the 80s. A quick google came up with these links and interestingly they are all based in Vic apart from the two links to this very forum.

    What is O.B. meant - please ? [Archive] - Woodwork Forums
    OB Timber - what does the OB stand for ? [Archive] - Woodwork Forums
    http://www.demar.com.au/images/struc...l%20Timber.pdf
    Timberzoo - Recycled Timber, Geelong, Melbourne, Flooring, Reclaimed, Floorboards.
    Ob hardwood
    Hardwood OB & F17
    Mitre10 Diamond Valley - Timberking
    Whittlesea Timber - Products
    MONTANA TIMBER HOLDINGS PTY LTD
    Welcome to Victorian Association of Forest Industries - About VAFI
    Timber.ews | PROVANS TIMBER
    Hardwood OB


    Tools

  22. #22
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    Looks like a Regional suppliers term to any normal person. How do you order timber when you want FSHWD as opposed to RSHWD, or another way of looking at is you could order or specify RSHWD anywhere in this country and they will know what it is whereas with the OB term you would have to explain your needs further, which leads to complications where there is no need to have any.

    regards inter

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