Closing a 200mm cavity with ply.

ando2891 · 21-05-2015 10:57am #1

Hoping someone can help me out here, I'm in the process of building a house with a 200mm cavity full filled with kingspan platinum board, 100mm block internal and external leaf. The reveals have been stepped back 75mm including the heads (which seems to be a bit too much, 50mm might have been better). if I now use 18mm ply to box off the cavity, how is this fixed where it butts against the outer leaf and vertical damp course??
Obviously I don't want to make a hole in this as that defeats the purpose of it being there! The plan is to then strap my windows to this ply and tape them for airtightness.

Has anyone used this method, or anyone able to give me any pointers?? Thanks.

galwaytt · 21-05-2015 4:21pm

Ply ? Just plain no. How long do you think that's going to last ??

ando2891 · 21-05-2015 4:52pm

What makes you think it won't last? It would be WBP. It seems to be an accepted construction detail now to prevent cold bridging at the reveals. Because the inner leaf is stepped back 75mm the plywood isn't exposed to the outside instead it butts against the vertical damp course,it's the fixing detail here that I'm not sure about and was wondering how others delt with it here.

JimmyMW · 21-05-2015 5:09pm

ando2891 wrote: »

What makes you think it won't last? It would be WBP. It seems to be an accepted construction detail now to prevent cold bridging at the reveals. Because the inner leaf is stepped back 75mm the plywood isn't exposed to the outside instead it butts against the vertical damp course,it's the fixing detail here that I'm not sure about and was wondering how others delt with it here.

WBP is used everywhere in buildings including roof parapets etc and there should be no issue with it in this location, I am planning on doing a similar detail and the plan is to put steel brackets on 18mm ply in the corners and fix it to the inside leaf, put a treated timber into the cavity sitting on the rising wall for support at the cill. then pump the cavity

893bet · 21-05-2015 5:56pm

JimmyMW wrote: »

WBP is used everywhere in buildings including roof parapets etc and there should be no issue with it in this location, I am planning on doing a similar detail and the plan is to put steel brackets on 18mm ply in the corners and fix it to the inside leaf, put a treated timber into the cavity sitting on the rising wall for support at the cill. then pump the cavity

Close with PIR. Then plaster board.

hexosan · 21-05-2015 6:02pm

be careful with the ply make sure it's certified marine ply

The_Bullman · 21-05-2015 9:10pm

893bet wrote: »

Close with PIR. Then plaster board.

What are the windows fixed to if you do this?

cork2 · 21-05-2015 9:16pm

893bet wrote: »

Close with PIR. Then plaster board.

+1 on this!! PIR is the way to go. Personally I'd never put ply in the cavity any dampness or moisture that reaches the outer leaf of block work will destroy the ply including WBP. WBP isn't what it was, the stuff around now is rubbish, delaminates with the first sign of moisture.

Rabbo · 21-05-2015 9:52pm

cork2 wrote: »

+1 on this!! PIR is the way to go. Personally I'd never put ply in the cavity any dampness or moisture that reaches the outer leaf of block work will destroy the ply including WBP. WBP isn't what it was, the stuff around now is rubbish, delaminates with the first sign of moisture.

How do you fix the windows to the reveal if the cavity is full filled with PIR? The dpc will stop the vast majority of moisture travelling from outer lead to ply. Marine ply should be able to deal with anything that would get through. You can also cut the ply 25mm short of the dpc and fit PIR strip in between. This will also help with thermal bridging

ando2891 · 21-05-2015 10:09pm

I assume you fix the window to the outer leaf if your closing with PIR? In reality this might be a better option for me as the full fill board is already flush with the inner leaf so what I'm really looking for is airtightness, where as the ply is a robust stop for if blown bead is being used. Has anyone personally used either of these details?

cork2 · 21-05-2015 10:24pm

Rabbo wrote: »

How do you fix the windows to the reveal if the cavity is full filled with PIR? The dpc will stop the vast majority of moisture travelling from outer lead to ply. Marine ply should be able to deal with anything that would get through. You can also cut the ply 25mm short of the dpc and fit PIR strip in between. This will also help with thermal bridging

If you cut your ply 25 mm slack of the dpc what holds it in place? The ply will move during construction, you'll never wedge it tight enough and in turn the window will move. I wouldn't fix windows to that detail for you at all! Windows get fixed to the block work, the window companies I've dealt with in the last twelve months have special extra long straps to account for the wide cavity. You fix the strap to the block work on the inner leaf with pins or screws. After that if you're not satisfied get a can minimal expansion foam when everything is done and foam the windows after they've been strapped to take away any bounce that's in them. Also it's almost standard at this stage to use an insulated cavity closer, these are plastic and therefor suitable to be put in the cavity, although in my opinion PIR does the same thing. Also for airtightness make sure you cover the whole window strap with tape!!

cork2 · 21-05-2015 10:33pm

ando2891 wrote: »

I assume you fix the window to the outer leaf if your closing with PIR? In reality this might be a better option for me as the full fill board is already flush with the inner leaf so what I'm really looking for is airtightness, where as the ply is a robust stop for if blown bead is being used. Has anyone personally used either of these details?

Nope you get long straps and fix to the inside leaf of the block work. If you're blowing bead in to the cavity get the plastic insulated reveal liners, you put them around the reveal, they sit over the block and you can glue the lip on to the block to keep them in place or if the block work isn't built they come with clips that you use to build them in, strap in your windows and tape onto the plastic liner.

cork2 · 21-05-2015 10:35pm

Also before using ANY detail on the construction consult you're engineer, it's his call. Nothing worse then taking out windows!!

galwaytt · 22-05-2015 10:35am

ando2891 wrote: »

What makes you think it won't last? It would be WBP. It seems to be an accepted construction detail now to prevent cold bridging at the reveals. Because the inner leaf is stepped back 75mm the plywood isn't exposed to the outside instead it butts against the vertical damp course,it's the fixing detail here that I'm not sure about and was wondering how others delt with it here.

I KNOW it won't last. We consume big qty's of plywood where I work on a weekly basis, and we are very careful about what we buy & use.

JimmyMW wrote: »

WBP is used everywhere in buildings including roof parapets etc and there should be no issue with it in this location, I am planning on doing a similar detail and the plan is to put steel brackets on 18mm ply in the corners and fix it to the inside leaf, put a treated timber into the cavity sitting on the rising wall for support at the cill. then pump the cavity

Sorry, but WPB as you know it, and as you think it would be, right now, is nothing of the sort. There is a huge problem with millions of m3 of cheap rubbish dumped in Europe from China, and nearly every provider has been caught out at some stage - it's not the providers fault btw.
I've seen entire roof's having to be removed and re-done inside the last 2 years on this issues alone.

hexosan wrote: »

be careful with the ply make sure it's certified marine ply

Marine ply is better than WPB, but still delaminates from the edge if damp. Quality of build essential here: in it's 'marine' application it would be finished as per quality joinery, furniture quality, and so it works well - where we're talking about is first-fix stuff on a building - not the same at all.

cork2 wrote: »

+1 on this!! PIR is the way to go. Personally I'd never put ply in the cavity any dampness or moisture that reaches the outer leaf of block work will destroy the ply including WBP. WBP isn't what it was, the stuff around now is rubbish, delaminates with the first sign of moisture.

Amen: this ^^^^^^

A non wood alternative such as Duripanel is one good alternative: http://www.tegral.com/uploads/docs/facades-and-building-boards/duripanel.pdf

Here's why a lot "WPB" in the market is rubbish: 'hand made' :rolleyes:

ht9zni1gs28crp · 22-05-2015 10:38am

Or if you have the time put a bit of pre thought into it.... prefix angles to the blocks and lintels. Your builder then builds in these specials around the jambs. Close the cavity with marine ply, solid detail. Proven.

The long straps back to the inner leaf are a cold bridge and ultimately defeating the object of all your insulation efforts....detail below. The straps for the windows are fixed to the ply rather than the inner leaf as shown. From this jamb detail the Galv angles were changed to 40x40x6mm. By using 200mm lengths of glav angles it makes it buildable and reduces further any cold bridging details.

ando2891 · 22-05-2015 11:39am

That detail looks good! Though is the vertical damp course pierced by the fixings holding the angle brackets to the wall?

dfader · 22-05-2015 1:00pm

Detail looks good but why the need for plywood when the window is not fixed to the plywood but is instead strapped to the inner leaf using long straps. Could you not have used PIR there instead? is it that the straps are also fixed to the plywood to stop them flexing?

ht9zni1gs28crp · 22-05-2015 2:20pm

dfader wrote: »

Detail looks good but why the need for plywood when the window is not fixed to the plywood but is instead strapped to the inner leaf using long straps. Could you not have used PIR there instead? is it that the straps are also fixed to the plywood to stop them flexing?

Re read my into sentence. We changed the strap to fix to the ply board rather than the blockwork in this instance. As out inner leaf around the windows is a Quinlite block. As most know they aren't the easiest to guarantee a fixing to.

ht9zni1gs28crp · 22-05-2015 2:42pm

ando2891 wrote: »

That detail looks good! Though is the vertical damp course pierced by the fixings holding the angle brackets to the wall?

The Damp course goes in after the brackets (attached to the block) The Damp course will then protect the edge of the Marine Ply as it will be tight up to the face of the Galv angle. Another positive for the 75mm step back. This equates to 90mm plus of coverage for the DPM.

cork2 · 22-05-2015 6:55pm

Ares Proud Production wrote: »

Or if you have the time put a bit of pre thought into it.... prefix angles to the blocks and lintels. Your builder then builds in these specials around the jambs. Close the cavity with marine ply, solid detail. Proven.

The long straps back to the inner leaf are a cold bridge and ultimately defeating the object of all your insulation efforts....detail below. The straps for the windows are fixed to the ply rather than the inner leaf as shown. From this jamb detail the Galv angles were changed to 40x40x6mm. By using 200mm lengths of glav angles it makes it buildable and reduces further any cold bridging details.

[IMG]http://i22.photobucket.com/albums/b319/Ares Proud Production/Housebuild/Jamb%20detail%20snipped_zps1dyztp4i.jpg[/IMG]

[IMG]http://i22.photobucket.com/albums/b319/Ares Proud Production/Housebuild/2015-02-12%2014.39.22_zps1qo9b5pv.jpg[/IMG]

I'll probably be given out to for this post but ye aren't listening to myself and galwaytt. When it comes to WBP or marine ply just STOP!! Do NOT put it in the cavity end of! Marine is ply and will still delaminate, I've been there and I've seen it! There are purpose made plastic insulated reveal liners. There not much more expensive than marine ply and if ye were that worried about cold bridging ye'll get them. Also it's my belief that WBP or Marine ply even if it doesn't get wet as such will be damp and will never dry out, therefore it will grow mould!!

As for long straps cold bridging, you're right ...........IN THEORY. But they won't actually affect it. The amount they'll cold bridge in minuscule. Plus if you use a 27mm insulated reveal liner inside you have no worries.

Also out of curiosity OP how experienced in these details is you builder and what was the detail that your engineer came up with? To be honest don't waste you money on plywood until you have cleared it with him, because not being smart but honestly any of the engineers I come into contact with day to day would make you remove it.

fatty pang · 22-05-2015 10:41pm

miller_63 wrote: »

Re read my into sentence. We changed the strap to fix to the ply board rather than the blockwork in this instance. As out inner leaf around the windows is a Quinlite block. As most know they aren't the easiest to guarantee a fixing to.

Indeed. The Quinnlite product guide recommendations for fixings states “a minimum penetration of 50mm into the blockwork and should be no closer to any edge of the blockwork then the length of the fixing”. This being the case any fixing into the face of a block on edge is not acceptable. Your angle cleats appear to be even closer.

Big windows - and even bigger doors - will result in high pulling loads on these fixings.
Never mind though… all these wide cavity details look great in THERM !

dfader · 22-05-2015 10:53pm

I haven't any calculations to prove it or THERM analysis images but would ask are quinnlites needed at the reveals in this case as the blocks are not returned to close the reveal like the old way of doing it and the 250mm gap is maintained, so if closed with either plywood or cavity closer they would still appear to be overkill. I understand and agree where quinnlites are used at other junctions where cold bridges occur such as ground floor and wall.

sydthebeat · 22-05-2015 10:56pm

dfader wrote: »

I haven't any calculations to prove it or THERM analysis images but would ask are quinnlites needed at the reveals in this case as the blocks are not returned to close the reveal like the old way of doing it and the 250mm gap is maintained, so if closed with either plywood or cavity closer they would still appear to be overkill. I understand and agree where quinnlites are used at other junctions where cold bridges occur such as ground floor and wall.

i was just about to post this.

the quinnlites on the internal leaf appear to be servicing no purpose (other than providing a plumb line and an easy cut block)

ht9zni1gs28crp · 22-05-2015 11:25pm

Lots of opinions which are good for debate. Proof and evidence surpass heresay all day long.

Jamb detail has been proven thermally with ease for passive certification and approved in general.

Overkill? Maybe in your book.....

Expensive fixings approved and specified for quinlite blocks. Overkill? Windows and doors main loading is off head and cill. Cill board sits on inner leaf for extra stability.

DPM....if its going to get SO damp in there why bother? Again evidence surpasses heresay. I would suspect poorly built and maintained details resulted in 'damp' cavity closers. Again proof and evidence will bolster your argument. I have encountered ten times more plus points to the negative ones regarding this detail.

So far the boards have survived damp free in an un rendered and unfilled cavity since January. Bone dry might I add.

And on that point....the amount of 'experts' that appear on a site is unreal. These same 'experts' are nowhere to be seen when the "cows come home"

cork2 · 23-05-2015 12:57am

miller_63 wrote: »

Lots of opinions which are good for debate. Proof and evidence surpass heresay all day long.

Jamb detail has been proven thermally with ease for passive certification and approved in general.

Overkill? Maybe in your book.....

Expensive fixings approved and specified for quinlite blocks. Overkill? Windows and doors main loading is off head and cill. Cill board sits on inner leaf for extra stability.

DPM....if its going to get SO damp in there why bother? Again evidence surpasses heresay. I would suspect poorly built and maintained details resulted in 'damp' cavity closers. Again proof and evidence will bolster your argument. I have encountered ten times more plus points to the negative ones regarding this detail.

So far the boards have survived damp free in an un rendered and unfilled cavity since January. Bone dry might I add.

And on that point....the amount of 'experts' that appear on a site is unreal. These same 'experts' are nowhere to be seen when the "cows come home"

After that cocky, smart assed comment I'm beginning to wonder why you'd bother asking for advice. Out of general curiosity on my own part are you doing a self build?

ht9zni1gs28crp · 23-05-2015 7:13am

cork2 wrote: »

After that cocky, smart assed comment I'm beginning to wonder why you'd bother asking for advice. Out of general curiosity on my own part are you doing a self build?

First off I didn't ask for your advise. I offered first hand real world evidence for a solution the OP asked for help with. I have already been advised by some of this countries top consultants so if that offends you and makes it read for 'smart assed' I'm not really going to lose any sleep over it.

Secondly if you can't provide real world evidence to your claims and or theory then its all a moot point is it not? You are adamant and shouting hellfire and brimstone re delaminating ply. All I have asked you to do is provide first hand evidence of this. Show us your detail, the install and the results and then I will take the issue up in more detail.

fatty pang · 23-05-2015 7:55am

Ares Proud Production wrote: »

Jamb detail has been proven thermally with ease for passive certification and approved in general.

The problem with windows & doors in the Passive certification process is that (undue) precedence is given to the thermal performance of the installation to the detriment of the physical robustness.
If 'computer says yeh' (window is in PHPP) then that’s generally all that matters.

Ares Proud Production wrote: »

Overkill? Maybe in your book.....

Rather the opposite...

Ares Proud Production wrote: »

Expensive fixings approved and specified for quinlite blocks. Overkill?

I had major difficulties getting anybody to stand over fixings less than 100mm from the edge of aerated blocks. You did very well to get somebody to approve fixings at less then 50mm.
If your cavity lining boards are physically robust then the straps are superfluous- you should have direct fixed through the frames into the lining boards. This is the optimum fixing method. Long straps are not good for anything that moves – particularly heavy triple-glazed doors.

Ares Proud Production wrote: »

Windows and doors main loading is off head and cill.

Oh dear....

fatty pang · 23-05-2015 7:56am

cork2 wrote: »

After that cocky, smart assed comment I'm beginning to wonder why you'd bother asking for advice. Out of general curiosity on my own part are you doing a self build?

Tired and emotional I think

BryanF · 23-05-2015 8:43am

.the amount of 'experts' that appear on a site is unreal. These same 'experts' are nowhere to be seen when the "cows come home"

fatty pang wrote: »

Tired and emotional I think

and we'll leave the personal comments for a different forum, thank you.

galwaytt · 23-05-2015 12:01pm

miller_63 wrote: »

Lots of opinions which are good for debate. Proof and evidence surpass heresay all day long.

Jamb detail has been proven thermally with ease for passive certification and approved in general.
Overkill? Maybe in your book.....

Expensive fixings approved and specified for quinlite blocks. Overkill? Windows and doors main loading is off head and cill. Cill board sits on inner leaf for extra stability.

DPM....if its going to get SO damp in there why bother? Again evidence surpasses heresay. I would suspect poorly built and maintained details resulted in 'damp' cavity closers. Again proof and evidence will bolster your argument. I have encountered ten times more plus points to the negative ones regarding this detail.

So far the boards have survived damp free in an un rendered and unfilled cavity since January. Bone dry might I add.

And on that point....the amount of 'experts' that appear on a site is unreal. These same 'experts' are nowhere to be seen when the "cows come home"

Not commenting on your detail generally, but your ply is dry because it's open to the air and masses of ventilation. Consider a fence post out in the open. It lasts for years despite constant cycles of hot/cold, wet/dry. But it's "ventilated". Where it rots is where it meets the ground: no ventilation.

It's when things get closed up that issues arise generally. Applies to all manner of things in a build.

hexosan · 23-05-2015 1:15pm

I think one of the issues Miller has is that on this site if you look for an opinion your slated for not engaging a professional, then when you do engage one your still slated

cork2 · 23-05-2015 7:18pm

miller_63 wrote: »

First off I didn't ask for your advise. I offered first hand real world evidence for a solution the OP asked for help with. I have already been advised by some of this countries top consultants so if that offends you and makes it read for 'smart assed' I'm not really going to lose any sleep over it.

Secondly if you can't provide real world evidence to your claims and or theory then its all a moot point is it not? You are adamant and shouting hellfire and brimstone re delaminating ply. All I have asked you to do is provide first hand evidence of this. Show us your detail, the install and the results and then I will take the issue up in more detail.

If you have competent consultants advice then ok, brilliant I'll stop arguing. Just make sure you have it on paper.

As for plywood, I am shouting and I'll keep shouting. Plywood is rubbish FACT. I have no intention of going to the trouble of getting pictures from the computers at work to show you delaminating ply wood. If you're currently involved in construction is this country you'll know only too well that this is a major issue as pointed out also by other posters. I'm not against you're whole detail just the Plywood. If you could use cement board or PIR or something I wouldn't have much against. It's logical Cavities are are damp and not ventilated please tell me why you think this is a good combination for wood?? Manmade wood product at that!!

Now I admit last night I shouldn't have called you smart assed or cocky. The OP asked a question and you gave your opinion. I've also given mine, we don't agree on the subject and I don't believe we will therefore I've argued long enough. Timber does not belong in cavities and putting it there is an unnecessary risk, we cover the roof timber to keep it dry and paint paint the front door for the same reason. This is my opinion and nothing else. As far as I'm concerned I won't be posting on this thread again or we'll start going around in circles. Best of luck whatever way you decide to go OP!!

cork2 · 23-05-2015 7:20pm

hexosan wrote: »

I think one of the issues Miller has is that on this site if you look for an opinion your slated for not engaging a professional, then when you do engage one your still slated

There's no harm in discussion and debate but once you have the options and the info a professional opinion is key!!! You don't know any of us are, don't take the risk!!

dfader · 23-05-2015 8:13pm

miller_63 wrote: »

Overkill? Maybe in your book.....

Yes, in my book....if you interested here is one of the books I read, which lead me to make that comment; http://www.greenbuildingstore.co.uk/page--denby-dale-passivhaus-technical-film.html
Theres a technical briefing you can get for this house - you have to apply and they will send you a copy.

The attached detail with which also has an image of the Isotherms through the junction also influenced my comment.

Interesting debate hearing the comments from those with experience about the quality of plywood products these days and the possible delaminating.

lownhard · 24-05-2015 4:52pm

Hi

My builder has used this plywood onsite. It is supposed to be marine ply. Is this marine ply? Seems rubbish.

http://www.img.ie/image/Zu2

http://www.img.ie/image/ZuM

http://www.img.ie/image/Zu6

cork2 · 24-05-2015 5:48pm

It would worry me that the writing on the tag is Chinese or something along those lines. From a picture to me that doesn't look like marine it looks like the stuff they're calling WBP these days. I can't say for sure whether it's high quality or low quality but it has a CE stamp on it. What is it being used for?

galwaytt · 25-05-2015 9:35am

lownhard wrote: »

Hi

My builder has used this plywood onsite. It is supposed to be marine ply. Is this marine ply? Seems rubbish.

http://www.img.ie/image/Zu2

http://www.img.ie/image/ZuM

http://www.img.ie/image/Zu6

cork2 wrote: »

It would worry me that the writing on the tag is Chinese or something along those lines. From a picture to me that doesn't look like marine it looks like the stuff they're calling WBP these days. I can't say for sure whether it's high quality or low quality but it has a CE stamp on it. What is it being used for?

Hard to say for sure: the label, frankly, could be printed by anyone - you'd actually have to see the certificate and see who was the notified body - there is nothing on that label about who certified it........ A brother of mine has worked for several notified bodies (UK, Netherlands, Germany), including visits to China, and tbh what he described would scare the bejasus out of you (and not in a wood industry capacity) - he actually refused to CE pass the factory in question..........

What worries me about your sample is the cross section. If you bear in mind you should have a single piece middle layer, why are there pieces or a void............see my photo from China for a possible reason. If your ply is just a good top & bottom veneer, but junk in the middle (offcuts, bark, bulked up with glue/sawdust), then it's only good for firewood.........

Nothing to stop you taking that piece of ply and taking it apart - now is the time to do it, not after it's up on the house.....

Btw, please tell me that the expanded corner bead in the pic is NOT because your plastering the ply.................

P.S. I've heard anecdotally certain people referring to CE in this context meaning 'China Export'..............

rampantbunny · 26-05-2015 4:00pm

Interesting thread. Moreso because I've a 200mm cavity, and have used marine ply to close the window and door reveals, behind which I friction fitted 100mm thick PIR board.

Before installing the ply I left some exposed to bad weather conditions at the start of the year. Some snow, frost, rain, drying out. Not just a week, but over 2 months.
Before fitting of windows, ply was in place (uncovered) for probably another month. It got wet, dry, wet again.
I could see no delamination.

Windows went in, and 2 months later, ply is uncovered internally in an unpumped cavity, therefore I imagine it is pretty dry. After windows were fitted, on outside I used good quality sealant to stick the vertical DPC to window frame where it overlapped. Subsequently plastered over this. Next task will be to clean where the plaster meets the window and apply another bead of sealant.

Will the ply deteriorate in the cavity - my understanding from the above posts is that it will because there is no ventilation.
I didn't think cavities were airtight...there is some air albeit maybe not enough to call ventilation. But don't I have to worry about the ply getting wet again and being unventilated before it becomes a concern.

ht9zni1gs28crp · 27-05-2015 10:18am

The pictures posted above are of stock Ply above are not Marine Grade Plywood AFAIK.

I have gone to the expense of Marine Grade Ply and not anything ordinary or cheap. I have since spoken with our plasterer, between us all we can see is one place for 'potential' water ingress. Now the water ingress level required to delaminate Marine Grade ply is an awful lot and in my instance will not happen bar a catastrophic event. All down to detailing and best practice install.

(a catastrophic event would harm all jamb details let alone a ply reveal)

Our only view on water/damp ingress into the cavity is between the Render seal to the frame. In our case we have quite a bit of frame hidden here so made sense to put in a waterproof mastic sealant here between the Unit and the rear of the DPM. On top of this the Render (which has its own waterproofer mixed in) provides the preliminary barrier to prevent water penetration as it is tight up against the window. Beyond this the mastic sealant provides a secondary barrier.

Beyond this there are no other areas for water ingress.

@cork2 Thank you for the clarity and the retraction of those comments. Debate is good and maybe we all get a bit heated, i know I do as im under pressure with the whole job etc etc. Anyways reiterating the comments earlier when I asked for evidence of Plywood delaminating in cavity in this detail, reading back this still hasn't been produced. Its okay to talk about stock ply delaminating when left exposed. We all know that happens and we agree with you that stock ply doesn't belong anywhere near the cavity, especially any cheap grade ply like you have shown. But in this instance is decent marine grade ply really going to suffer like you say? I would be interested to know which project you pulled the delaminated marine grade ply out of the cavities, and if possible id like a chat with the owner to see what he/she would have done different? Pictures of before and after would be interesting of this install you refer to.

galwaytt · 27-05-2015 8:33pm

miller_63 wrote: »

The pictures posted above are of stock Ply above are not Marine Grade Plywood AFAIK.

I have gone to the expense of Marine Grade Ply and not anything ordinary or cheap. .

May I ask how you know that the ply you used is actually marine spec? (genuinely curious)

The issue that the industry has atmo is that a no of the markings and supporting paperwork is of dubious origin. Traceably certified ply is fine if that's what you actually get, but it is in the minority in supply.

ht9zni1gs28crp · 28-05-2015 8:18am

galwaytt wrote: »

May I ask how you know that the ply you used is actually marine spec? (genuinely curious)

The issue that the industry has atmo is that a no of the markings and supporting paperwork is of dubious origin. Traceably certified ply is fine if that's what you actually get, but it is in the minority in supply.

Its stamped, its traceable and the assurance of one of the leading suppliers in the country.

This is not a 'done deal' or 'adverts' built house BTW

Do you want me to video a boil test on it?

cork2 · 28-05-2015 6:38pm

miller_63 wrote: »

Its stamped, its traceable and the assurance of one of the leading suppliers in the country.

This is not a 'done deal' or 'adverts' built house BTW

Do you want me to video a boil test on it?

You're not grasping the seriousness of the plywood issue. The leading suppliers in the country are stocking the rubbish!! One nationwide timber importer is selling it and the largest builders providers in munster, they're selling it as marine and as WBP!! You don't need to be doing a "donedeal house" to get caught.
I don't need to see a boil test it makes no difference to me either way. I'm not try prove anything I'm simply pointing out that a major issue exists if you're happy you managed to get the real deal then you are one of the lucky ones.

ht9zni1gs28crp · 29-05-2015 9:14am

cork2 wrote: »

You're not grasping the seriousness of the plywood issue. The leading suppliers in the country are stocking the rubbish!! One nationwide timber importer is selling it and the largest builders providers in munster, they're selling it as marine and as WBP!! You don't need to be doing a "donedeal house" to get caught.
I don't need to see a boil test it makes no difference to me either way. I'm not try prove anything I'm simply pointing out that a major issue exists if you're happy you managed to get the real deal then you are one of the lucky ones.

You're not reading the responses or considering the detail in greater depth, all you can see is the word 'ply' and immediately start the same spiel again and again..

That's fine, I do grasp the seriousness but the more I tell you the Marine Ply I have on site is fine the more you keep coming back 'stocking rubbish' and delamination within cavities. Its not a general comment its become specific and personally directed. So the more I want to see proof to back up your claims.

I do agree with the major issue and that it needs highlighting as I guess so many other people would be unaware on how to check/tell. One sure fire way to tell how genuine a ply board is the price. I know I could have bought a cheaper alternative and therein lies the problem.

The problem here is you are swinging the tar brush at everyone and dismissing everything else as wrong.

rampantbunny · 29-05-2015 9:34am

miller_63 wrote: »

One sure fire way to tell how genuine a ply board is the price. I know I could have bought a cheaper alternative and therein lies the problem.

To be fair Miller_63, that won't qualify as a sure fire way in this fair country of ours. It would suggest that paying a high price always guarantees the best product.

Cork2...on the other side, and I'm not mediating here, how damp is the cavity going to get in reality if the detail miller has described is executed correctly?

galwaytt · 29-05-2015 3:41pm

miller_63 wrote: »

... One sure fire way to tell how genuine a ply board is the price. I know I could have bought a cheaper alternative and therein lies the problem..

...you were doing OK until you said ^^^^

There is no warranted correlation between price and the quality.

There is price, and there is quality. Two different subjects. One is variable, one is objective.

As cork2 says, you can buy the ply wherever you want, but many reputable suppliers have been caught out too.

There is a very large qty of so-so plywood sitting in the likes of Rotterdam looking for a 'home', and so caveat emptor. I had a seller in to me yesterday offering me ply, WPB and OSB in any quality and size including (and I quote) "shyte from China". When I asked if people are still buying it he told me that there's a market for resale for those who are only interested in the price.

So, you can do a boil test if it makes you feel better- at least you know what that is: think of all the others who don't, or shouldn't need to tbh.

cork2 · 30-05-2015 1:09pm

Ares Proud Production wrote: »

You're not reading the responses or considering the detail in greater depth, all you can see is the word 'ply' and immediately start the same spiel again and again..

That's fine, I do grasp the seriousness but the more I tell you the Marine Ply I have on site is fine the more you keep coming back 'stocking rubbish' and delamination within cavities. Its not a general comment its become specific and personally directed. So the more I want to see proof to back up your claims.

I do agree with the major issue and that it needs highlighting as I guess so many other people would be unaware on how to check/tell. One sure fire way to tell how genuine a ply board is the price. I know I could have bought a cheaper alternative and therein lies the problem.

The problem here is you are swinging the tar brush at everyone and dismissing everything else as wrong.

You're 110% right, all I'm seeing is the word "ply" and instantly I think "problem". It's a problem with may never arise but why risk it when your detail is perfect using a purpose made insulated cavity closer. As for swinging the tar brush you're right again, simply because I'm at the point where I don't trust ply. Get it from any stockist you like at two hundred euro a sheet and I wouldn't put it anywhere in a house that it can't be easily removed. Also this isn't personally directed. Look we're not getting anywhere, this argument is ridiculous. We don't agree and we won't.

893bet · 30-05-2015 1:26pm

What are the insulated cavity closers you mention?

The only one I could find was Kingspan and when I handled the product I found them to be flimsy and very expensive. I have 150mm cavity and closed with PIR cut to fit tightly.

cork2 · 30-05-2015 2:53pm

893bet wrote: »

What are the insulated cavity closers you mention?

The only one I could find was Kingspan and when I handled the product I found them to be flimsy and very expensive. I have 150mm cavity and closed with PIR cut to fit tightly.

I too would use PIR, but yes it's the expensive kingspan and other brands are what I was talking about. They seem to be what the majority of Architects and Engineers I'm dealing with are specifying. A plastic profile with a strip of 25mm PIR slipped into them and you build them into the blockwork and them tape the windows onto them. They're only flimsy until they're in place.

sydthebeat · 30-05-2015 3:04pm

havent seen those cavity closers in anything over 150mm cavity widths.

in this whole thread, has anyone asked what the function of the ply box system is?
if its just to close the cavity, the PIR would be a much better choice.
if its to provide structural stability to the windows, have engineers passed this?

rampantbunny · 02-06-2015 3:57pm

sydthebeat wrote: »

havent seen those cavity closers in anything over 150mm cavity widths.

in this whole thread, has anyone asked what the function of the ply box system is?
if its just to close the cavity, the PIR would be a much better choice.
if its to provide structural stability to the windows, have engineers passed this?

Marine ply in mine is to close the cavity (with PIR directly behind), but to also support the windows. They are 3G inward opening and tilt (tilt/turn) so pretty heavy.
I have alu angle within the cavity to support the ply. The ply can also be used as part of the airtightness fabric provided the windows are properly taped to it and holes sealed etc. probably easier to run membrane the whole way around the reveal though.

My engineer was happy for me to build a wall that supported itself in mid air. He saw the detail around the window and wasn't interested either way.
I'm still looking for floating blocks syd so if you come across any, let me know.

Strolling Bones · 02-06-2015 4:06pm

rampantbunny wrote: »

I'm still looking for floating blocks syd so if you come across any, let me know.

I see what you did there

Closing a 200mm cavity with ply.

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