fiberglassing residential deck - waterbased epoxy? wtf?

[cam 0]

I am replacing our exterior wooden deck with a membrane deck (plywood with waterproof walk-on membrane on top). Mainly so I can use the underneath as a carport/workshop area for parking and building boats etc...

 

I see there are many proprietary membranes such as nuradeck, dexx and trafficguard.... Most seem to be chopped strand mat and water based epoxy of some kind, and about $70-80/ square meter plus. As the deck is quite large, 80 sqm, this is quite a big bag of money I would rather spend on something else.

 

Also the advice from the companies makes me worried how tuff they really are: such as "do not use a waterblaster to clean as this may damage the deck membrane... do not allow water to pond as this will damage the deck membrane...."

 

I am pretty sure a epoxy/cloth deck would stand up to a fair bit of water blasting and water ponding.

 

I am thinking of using 300gm chopped strand mat and epoxy. Seems to be a much tougher and cheaper solution on the face of it. Also I can apply this myself, as the proprietary coatings require using their applicators (fair enough I suppose to protect their reputation from dodgy installs).

 

Just wondering if epoxy will adhere to tanalised ply ok or if anyone knows about any issues with this?

 

Also are those water based epoxies used in boatbuilding these days, or purely a 'non-marine' product for domestic use that is just designed to be safer and easier to handle for application? ie Why would one use a water based product given epoxy is well proven, well understood and tough?

 

Cheers for any info/opinions on this. I have done a reasonable amount of fiberglassing with woven cloth (altho nothing as large as this in area) but not familiar with water based epoxy at all.

[Guest]

I effing hate enclosed (waterproof) decks they are a leak waiting to happen. I realise in your case that may not be the end of the world but if they leak into the deck framing space and the water cant get out you are going to end up with deterioration of the framing guaranteed.

 

If you must have a waterproof deck I would recommend a flexible rubber membrane (Butynol or similar) rather that inflexible fibreglass one. The glass ones all seem to crack at the edge upstands. Remember your timber deck is flexible. Nothing you can do about that.

 

In your case why not fix profiled metal roofing (I would recommend corrugated) to the underside of the deck. Put some packers between the deck framing and the roofing to create some fall on it and a gutter at the low end. Eazy Pezy and way cheaper. You can flash the high end and sides to the deck for additional weathertighness if you want.

[cam 0]

thanks for this B, yes agree your suggestion has some nice advantages, and we might end up doing just that. The existing deck has this in part actually.

 

However we have to rebuild much of the deck anyway, as it is at the end of its life (25 years), and needs a new balustrade, and we want to make it all one level (currently split).

 

So while doing this work I am looking into how viable it is to use a waterproof deck membrane of some kind so the waterproofing is integrated.

 

It is a totally exterior deck, attached to the house for structural purposes only. Under deck is exposed so plenty of ventilation and visibility of any water penetration issues.

 

thanks for the information they usually crack at the edge upstands in your experience. Is this the house side upstand, where the membrane is installed behind the cladding, which seems to be the 'standard' aproach? I was planning on keeping the deck surface 12mm off the cladding, so the council consider it an external deck and don't care too much what I put on it (otherwise I really need to use an 'approved solution' ie Branz approved, to be consentable). I was going to waterproof this house to deck joint using a timber weather strip of some kind (eg quad or coving), surface mounted in sealant to keep some flexibility there.

 

but cost wise have accepted this will be many times your suggestion, just trying to get some info on how much more before deciding...

 

Cheers.

[Guest]

thanks for the information they usually crack at the edge upstands in your experience. Is this the house side upstand, where the membrane is installed behind the cladding, which seems to be the 'standard' aproach? I was planning on keeping the deck surface 12mm off the cladding, so the council consider it an external deck and don't care too much what I put on it (otherwise I really need to use an 'approved solution' ie Branz approved, to be consentable). I was going to waterproof this house to deck joint using a timber weather strip of some kind (eg quad or coving), surface mounted in sealant to keep some flexibility there.

 

All true Cam and if you really want a waterproof deck in your case with the deck separate from the dwelling there is no real danger. I would still recommend a rubber membrane tho. The rigid glass ones just seem incompatible with the flexible deck structure. Remember if the framing is exposed from the underside you will get movement in the structure as the weather changes from dry to wet. Moisture in the air is enough. What will this do to the ply substrate and the rigid glass on top? This is the primary cause of failure of these types of decks. However if its only a carport anyway is there any real advantage in having a fully waterproof roof?

 

If it where me I would be designing the new deck around a metal roof under it. You can make a nice job of it and you get the same result.

[w44vi 17]

Just keep in mind that you must be an approved applicator to comply to your councils building code

[cam 0]

cheers w44vi, yes so I have discovered, altho if i keep the deck external from the building envelope, they don't care too much what I or anyone else put on it.

 

If it was an internal deck (ie. over a habitable part of the house) different story and I need to use an 'approved solution' which in general means BRANZ have approved the solution and it is applied by an approved applicator.

 

Mostly I am curious if water based epoxy have properties, that solvent based ones don't, and why all the approved solutions are water based epoxy.

 

I have read on one forum that the water based epoxies are thinner and more permeable in general (not sure how accurate this information is).

 

Wondering if perhaps they are more flexible as well?

[too_tall 15]

In your case why not fix profiled metal roofing (I would recommend corrugated) to the underside of the deck. Put some packers between the deck framing and the roofing to create some fall on it and a gutter at the low end. Eazy Pezy and way cheaper. You can flash the high end and sides to the deck for additional weathertighness if you want.

 

While I don't disagree with your comments about decks leaking and being a pita, this suggestion will be just as bad, I am afraid. Why do I know? I have about 140m2 of decking with a leaking roof underneath it. And a quote of $50K to fix the problem. The steel has rusted because leaves fell through the timber deck, and then rotted on the steel, releasing acidic compounds, which have made the steel roofing a sieve as opposed to a waterproof barrier.

 

I am not sure what is a better method, but steel right under the deck is not a great system unless your able to make sure nothing will sit on it and rot.

[TimW 1]

A couple of things I know.

 

If you are wetting Out CSM with Normal Epoxy it needs to be Powder Bound CSM.

 

Most CSM is Emulsion Bound and requires the Styrene in Polyester or Vinylester resin to break it down.

 

Normal Epoxy is not very good over top of Tanalised Ply.

If you Prime the Surface of Untreated ply before applying Your Cloth you get a decent amount of Epoxy soaking into the surface of the wood. If you have time you can even slightly thin the Epoxy with 5% Epoxy Thinners to get better penetration. (If you put the thinned coat on first let it dry, denib it with a quick sand, before wetting out your Cloth)

 

The Tanalising kind of stops this penetration and the two things (Epoxy and Tanalising) don't stick together very well.

[cam 0]

...

Why do I know? I have about 140m2 of decking with a leaking roof underneath it. And a quote of $50K to fix the problem. The steel has rusted because leaves fell through the timber deck, and then rotted on the steel, releasing acidic compounds, which have made the steel roofing a sieve as opposed to a waterproof barrier.

 

I am not sure what is a better method, but steel right under the deck is not a great system unless your able to make sure nothing will sit on it and rot.

 

Gosh that sounds expensive, thanks for that tt. I assume your roofing is built into the deck somehow that makes it an expensive fix. Where we have roofing under the deck at present, it is covered in crap actually, but it is just nailed up from below so should be easy to replace if and when it corrodes.

 

However if I did take this 'roofing underclad' approach again, I was planning on using clear corrugated polycarbonate to keep some light coming through the decking, and so I can see when it needs a hose out.

[cam 0]

A couple of things I know.

 

If you are wetting Out CSM with Normal Epoxy it needs to be Powder Bound CSM.

 

Most CSM is Emulsion Bound and requires the Styrene in Polyester or Vinylester resin to break it down.

 

Normal Epoxy is not very good over top of Tanalised Ply.

If you Prime the Surface of Untreated ply before applying Your Cloth you get a decent amount of Epoxy soaking into the surface of the wood. If you have time you can even slightly thin the Epoxy with 5% Epoxy Thinners to get better penetration. (If you put the thinned coat on first let it dry, denib it with a quick sand, before wetting out your Cloth)

 

The Tanalising kind of stops this penetration and the two things (Epoxy and Tanalising) don't stick together very well.

 

excellent thanks Tim. hmmmmm, that is what I was afraid of.

I did have one manufacturer claim tanalised ply is no problem for their product to stick to, but I wondered in practice if it can be tricky (or success can be a bit 'mixed' depending on how much penetration you can get with a primer coat).

 

Thanks for the info.

 

Some of the water based ('approved solution') products go straight on the tanalised ply and some seem to prime with paint before their product goes on. These can't provide terribly good penetration either I would have thought. esp compared to trad epoxy on marine ply.

[Guest]

Just keep in mind that you must be an approved applicator to comply to your councils building code

 

 

B*lls*it there is no such thing as a council approved building code. It is a national building code. All Building Consent Authorites (Councils) must approve consent applications against the New Zealand Building Code. This has been the case since 1992.

[Guest]

While I don't disagree with your comments about decks leaking and being a pita, this suggestion will be just as bad, I am afraid. Why do I know? I have about 140m2 of decking with a leaking roof underneath it. And a quote of $50K to fix the problem. The steel has rusted because leaves fell through the timber deck, and then rotted on the steel, releasing acidic compounds, which have made the steel roofing a sieve as opposed to a waterproof barrier.

 

I am not sure what is a better method, but steel right under the deck is not a great system unless your able to make sure nothing will sit on it and rot.

 

How old is the roofing? If you use prepainted profiled metal I would expect 15/20 years unless it was an extremly corrosive envrionment. Realistly you probably wont get much more that that out of a waterproof membrane no matter what the manufacturers say.

 

You have a fair bit of roofing there but 50k is a hell of a lot. There is probably only 15k of roofing. Where is the rest going?

[Guest]

cheers w44vi, yes so I have discovered, altho if i keep the deck external from the building envelope, they don't care too much what I or anyone else put on it.

 

Quite frankly thats a big call by the council. Their call of course but the law requires the deck to be built in accordance with the Building Code. Presumably the deck is more than 1.5m above the ground so Council have to isue a Building Consent which means they have to be sitisfied on reasonable grounds compliance with the NZBC Is being met. How can they be satisfied if its just a bunch of products you have put together? I wouldn,t but as I say its up to them.

[wheels 543]

It does depend on the grade of tanalising.

A good ruff sand with 40 or 60 grit will rip the timber enough to get a grab. It's not a boat after all, so it is not as important as adhering to a ply hull. Even if it comes away, it should still be waterproof. But hopefully it never comes away. And as already said, a coat of epoxy resin and solvent and I would go for 10%, will allow the resin to soak in and create a key.

 

Water based epoxies used in waterproof membranes are a different beast to the Resins we use on boats. Chalk and cheese. It'slike Enamel based paint and the enamel you find on a Bath tub.

Water or Turps or Solvent is purely a means of keeping the coating liquid and allowing you to get that liquid from the container to the surface you are coating. After that, it evaporates away and allows the fun to start. But it has nothing to do with what the actual coating becomes or behaves once it had it's party and has gone solid. the only real choice of the type of solvent is in what the base property of the coating is and what it is therefore missible in.

[w44vi 17]

Just keep in mind that you must be an approved applicator to comply to your councils building code

 

 

B*lls*it there is no such thing as a council approved building code. It is a national building code. All Building Consent Authorites (Councils) must approve consent applications against the New Zealand Building Code. This has been the case since 1992.

 

sorry I am not the best writer

 

you are quite correct the councils do not write the NZBC the councils enforce it

 

In this instance we are dealing with E2 External moisture http://www.dbh.govt.nz/UserFiles/File/P ... r-2011.pdf

 

Quote from E2

 

"It is important that product suppliers, manufacturers and NZ agents (for imported products) ensure those handling and applying their products are adequately trained to do so"

 

Porirua city council require a producer statement, a workman ship warranty and the applicators license number for you to get a code of compliance

 

Of course this is all based on the assumption that a permit is being sort

[cam 0]

Quote from E2

 

"It is important that product suppliers, manufacturers and NZ agents (for imported products) ensure those handling and applying their products are adequately trained to do so"

 

Porirua city council require a producer statement, a workman ship warranty and the applicators license number for you to get a code of compliance

 

Of course this is all based on the assumption that a permit is being sort

 

Yep it is consentable and I am planning to get building consent.

 

I think the councils (preliminary) view on the membrane I used came down to the fact it really is an external deck. As long as it truly is an external deck outside the building envelope, with no concealed spaces or cavities where moisture can cause problems, and even if it did get in, the consequences of failure do not affect the building or structure itself. The E2 concerns about "...external moisture entering the building" were addressed.

 

However they may have a different view when I task again who knows. That was the initial view they gave me anyway.

 

They do care how it is structurally attached of course and the e2 compliance there.

 

It does depend on the grade of tanalising.

A good ruff sand with 40 or 60 grit will rip the timber enough to get a grab. It's not a boat after all, so it is not as important as adhering to a ply hull. Even if it comes away, it should still be waterproof. But hopefully it never comes away. And as already said, a coat of epoxy resin and solvent and I would go for 10%, will allow the resin to soak in and create a key.

 

Water based epoxies used in waterproof membranes are a different beast to the Resins we use on boats. Chalk and cheese. It'slike Enamel based paint and the enamel you find on a Bath tub.

Water or Turps or Solvent is purely a means of keeping the coating liquid and allowing you to get that liquid from the container to the surface you are coating. After that, it evaporates away and allows the fun to start. But it has nothing to do with what the actual coating becomes or behaves once it had it's party and has gone solid. the only real choice of the type of solvent is in what the base property of the coating is and what it is therefore missible in.

 

Cheers wheels, interesting. Yes a roughening as you suggest will allow at least a decent mechanical bond if nothing else. So they are similar enough to be called epoxy but really different stuff? I know alot of research has gone into acrylic paints over the last few decades. maybe it has allowed the creation of these epoxies to be more worker/consumer friendly.

 

Mostly I am curious what mechanical properties the cured water-based product has that differs from traditional epoxy. If they claim it should not be waterblasted or have water ponding on it this may be just to cover themselves (unlikely I'd say) or may be it is much softer and more permeable than what 'we' call epoxy.

 

I also wonder why they dont use 'real' epoxy in this area more commonly.

[Guest]

Have you considered ferro cement?

[cam 0]

Have you considered ferro cement?

 

hmmm. no I had not actually.

 

I presume you mean on top of structural ply? or a total rebar and mesh structure? Is this a technique you have seen used in residential decks ? keen to know more about it actually.

 

I really like the maintenance properties of concrete itself and I was keen on a structural steel and concrete deck originally, but this could not join to a timber frame house, and would require steel portals at 90 degrees to the house, taking up alot of useable room underneath for structural steel.

[wheels 543]

Mostly I am curious what mechanical properties the cured water-based product has that differs from traditional epoxy.

It is more about ease of application and cost. It is cheaper to use those membranes and you roll or spray the stuff on and then easy to clean up applicator equipment. Two pot Resins is a different story. You have to mix, have a limited use time frame, have an issue with thickness due to heat biuldup, it's expensive, you have to use solvents to clean equipment and so on and so on. Resin is not UV proof, so you have to topcoat anyway. The membrane coatings are not structural, they have to have a good solid base to be applied to.

[cam 0]

Yes I guess usability rules in a large scale domestic applications where they want to ensure their product is reasonably foolproof to apply.

 

and cheaper I guess (to manufacture anyway), although it was the cost which made me wonder, as I reckon I can do 80m2 of traditional epoxy with 1 payer of chopped strand mat for around $2k.

 

That is allowing for 1.5L of resin per square meter overall. (primer coat, glass cloth coat, 2 top coats). plus a bit for painting.

 

I cant buy the water based product to apply myself so cant compare directly, but the price quoted installed is around $80 sq/meter = $6.4k.

 

If I get what I think is a better product and it is cheaper it is very appealing, but wondering if I have missed something about the membrane products that justifies their use.