Waterproofing Ideas for an Elevated Wooden Waterway Flume 1

[STrctPono]

I'm hoping to get ideas from some of you folks that may have experience with similar situations. We are rebuilding several waterway flumes and utility bridge crossings and there is one small flume in particular that needs to remain constructed out of wood for historic reasons. I think we can convince them to utilize fiberglass reinforced synthetic lumber but the issue is how to waterproof it. They currently are using a thick pond liner but it hasn't faired too well over time and is easily prone to vandalism. I'm looking for some ideas of how to waterproof the inside of the flume, keeping in mind that the flume structure needs to transition to a concrete lined channel at each end. If the pond liner really is the best thing, I suppose we could embed the end of the liner in the concrete bulkheads we will be pouring at the inlet and outlet.

 

[phamENG]

No experience but thought I might throw it out there: what if you lay up a fiberglass liner inside the wooden flume? Sort of like a really long boat in female form.

 

[STrctPono]

PhamENG. I like that idea and thought about it too but then wasn't sure what the reality of having a custom built single piece inverted trapezoidal shaped fiberglass liner installed really was. I do like the idea if I knew there was someone who could make it.

Total flume length is about 22ft.

The more I think about it, I wonder if they could do the fiberglass liner by doing a wet layup system and building the liner by saturating dry fiberglass sheets and laying them in place similar to how we do externally bonded FRP repairs....

 

[phamENG]

Yep. That's what I was thinking. Build the fiberglass in place.

 

[phamENG]

Make sure you spec a good coating on it. I don't believe uncoated fiberglass lasts very long under direct sun exposure.

 

[STrctPono]

Good idea! And yes, you're right, the resin does degrade with UV exposure. I will need a coating that is durable enough to handle long term abrasion.

 

[Wallache]

Stainless steel sheets would also work as a protective layer over the waterproofing.

 

[Compositepro]

Bonding fiberglass to wood can work if the wood is completely encapsulated, but not if the wood will get wet. A rubber liner and a stainless sheet metal flashing to protect the rubber should work.

 

[phamENG]

Compositepro - what if you didn't try to bind it, but just used the wood as a form? Water could get in between, but with the outside of the wood open it can dry again. And the same problem exists with a rubber liner and stainless sheets. Or is there another issue you're worried about?

 

[JedClampett]

My friendly Sika rep was here the other day pushing a waterproofing liner called Sikagard 7600. It goes on 120 mils thick and is somewhat flexible.

 

[STrctPono]

Bonding fiberglass to wood can work if the wood is completely encapsulated, but not if the wood will get wet. A rubber liner and a stainless sheet metal flashing to protect the rubber should work.

That's interesting. The wetting of the wood will debond the fiberglass? I plan on using a synthetic lumber instead of actual wood. Link

It's just that the current design utilizes a rubber liner with metal flashing and it isn't fairing so well.

 

[HTURKAK]

The crows ( they are very big and agresive in my zone ) disturbing the membrane roof gutters , seals of sandwich panels , glass roofs..

If the flume structure transition from concrete lined channel, I would prefer flume structure also with concrete lining say 50 mm on the membrane water proofing ..Other options, GRP lining or galv sheet lining seems viable..