Be interested to hear comments of the relative merits of either. On the face of it 12mm ply ain't a lot dearer than 12mm gib but must surely be way stronger. Plus a lot easier to work with and can be as easily undercoated/sealed as gib.
_atomant_,
May 24, 9:16pm
Sparky here, did a house in Thorndon, Wellington recently, owner was an engineer and at least one wall in each room was ply, He did not need to use any braceline and his rational was the structural strength left everything else behind,
johotech,
May 24, 9:29pm
So what do you think you are going to do with the joins?
moltenfire,
May 24, 10:38pm
Glue to studs, screw with gibscrews (or nailgun 40mm flatheads) then fill then gently belt-sand. I guess it depends on what the covering is to be - less critical with wallpapers but at this stage thinking semi-gloss paint.
johotech,
May 24, 10:51pm
Doesn't sound like a successful plan to me, even with wallpaper.
Ply is going to expand and contract with varying humidity. The joints will crack unless taped (like gib) and it will be difficult to tape without the tapered edge.
By "fill" I presume you mean builder bog. That will definitely crack. Sanding with a belt sander then applying semi-gloss paint will certainly show up every defect.
Some people use MDF on walls with arrised edges, but it is extremely hard to make the sheets look flat and even without filling the joints, the paint will still crack at the joints because of expansion & contraction.
You have to keep in mind that the Gib systems have been developed over many years to provide smooth paintable surfaces, so you're not going to be able to just come up with a better system over a cup of coffee and a few posts on the message board.
What are you actually trying to achieve? Lower cost? Stronger finish for student flats? Or something else?
tweake,
May 24, 11:00pm
the use of ply on walls as bracing elements is not uncommon. granted i never saw them after they where painted. however don't they have bracing gib now ?
i think its kinda funny how they do all this sheet bracing and then we come along and put holes in it !
moltenfire,
May 24, 11:02pm
By filler, would use epoxy based filler - gaps will be set at 2mm so edge strength sheet-sheet will be stronger than mid-sheet. Trying to achieve - sheer strength and something that won't disintegrate with a shake. Why do we build houses out of compressed chalk anyway? Actually, looking up the co-efficient of expansion of ply, the biggest factor is moisture content as temperature makes very little difference. That said, I doubt the mc would vary much in a dry house. Some interesting thoughts.
moltenfire,
May 24, 11:05pm
Yea my understanding is that the gib bracing is designed to crumple after the stress so needs replaced. Anyone had experience of this?
iluvmuse,
May 24, 11:19pm
The newer DOC huts are lined with ply and then poly'd. Paint will highlight the rough surface.
johotech,
May 24, 11:21pm
Ok, sounds like you have it all planned then.
Of course Braceline or Aqualine are much stronger than regular gib. They have fibre reinforcing in the core. Higher price for those products though.
Building houses out of compressed chalk? As I said, a lot of research has gone into these products for strength & durability - while aiming for a smooth, crack free (under normal circumstances) paintable finish. Easy to repair as well.
As for cutting holes Tweake, there are specification about where holes are allowed in bracing walls (like electrical outlets for example).
For disintegrating in a shake, not sure what you expect to achieve. Earthquake design needs to be a ground up process. It would be difficult to retrofit to the same standard. For example, if you made your house a rigid box, then your box would damage the foundations if they were the weakest point. Other considerations such as a heavy roof (concrete tiles), or a light flexible roof (steel) are also taken into account with earthquake design.
In Japan for example, older houses were a flexible design - 4x4 post and beam frame with low strength lining. The houses flex in a quake. The problem they had was their very heavy roofs. In a big, long quake, the frame flexed so much that the roof pancaked down and collapsed into the structure (like the CTV building). They still build the houses to the same framing designs now, but put a light weight roof on.
Maybe you'll be able to make a huge amount of money if your system works!
johotech,
May 24, 11:23pm
Usually the ply bracing elements are gibbed over aren't they?
tweake,
May 24, 11:41pm
don't think so. i was running cables at the time so they could have double gib the walls after. the ply was on the outside of the framing like gib, not internal in the wall.
mm12345,
May 24, 11:48pm
Pretty normal in architect designed houses in Chch now to use structural ply sheets over all the external framing. I re-clad our (formerly brick) house and did just that, batts in all external walls, building paper, 9mm structural ply screwed to framing @ 150mm centres on the edges, 300mm on the centre studs. As well as getting rid of about 50 tonnes of brick veneer, the ply adds a massive amount of bracing.
annies3,
May 24, 11:49pm
Any gloss at all will increase the visibility of any imperfections, try some on ply and see the effect before you start.
mm12345,
May 24, 11:51pm
Yes - if it's cracked - it needs to be replaced. Fletcher EQR tried to get away with raking and filling cracks, but were condemned for that practice by their sister company.
We just did a room out with that grooved interior ply painted it all out a whitish colour filled the joins with gap filler looks great we did ceiling and walls had seen it up in a few places and liked it plus we live way out of town and it was becoming a pain to try and get tradesman plasterers to come out here so this was a good option I like the look of it would use it again.
missymoo1000,
May 25, 1:31am
From an aesthetics perspective, I think ply looks very batch like and I don't like the finish.
zoopa,
May 25, 1:49am
I think so too, IF pine ply is used. There are some very nice ply's out there made from other timbers
jonners2013,
May 25, 2:26am
cavity?
moltenfire,
May 25, 2:27am
True but I've experimented a wee bit with two coats (brushed) of Sureseal followed by a light sand then two coats (rolled) of very flat non-gloss topcoat. can't see the grain anywhere.
moltenfire,
May 25, 2:27am
Yeah the blurb says that once it's taken a hit it's shagged.
biddy6,
May 25, 2:28am
x1
We used 7mm ply with the tongue and groove look in the kitchen and bathroom, its painted and still very hard to see any joins, and still looks very good.
moltenfire,
May 25, 2:35am
Not 100% just interested to hear the various angles before making the decision.
[quote=Earthquake design needs to be a ground up process. It would be difficult to retrofit to the same standard. For example, if you made your house a rigid box, then your box would damage the foundations if they were the weakest point. Other considerations such as a heavy roof (concrete tiles), or a light flexible roof (steel) are also taken into account with earthquake design. [/quote]
Yep 100% agree. But as a retrofit, if we get a big enough shake to damage the foundations, I'd rather that they let go but the house stayed up than vice-versa. House has typical long-run iron on roof so no heavy tiles. again why would anyone build an upside pendulum by using concrete tiles?
moltenfire,
May 25, 2:40am
I like it but too much varnish for my liking. shame the Local Body's here wouyldnt allow us to do that sort of build!
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