Waterproofing Corrugated Decking Before Concrete
We are working on a build right now where the owners have a vault that sits below their rear patio. The engineered plans call for several beams, corrugated metal decking on that, studs welded through to connect the decking to the studs, then 7″ of concrete.
We want to waterproof this thing, but not of my subs have given me a viable solution. The issue here are all the studs that sit on the decking. Normally I’d look at something like 60mil EPDM, but the studs make this impossible. Old school visqueen will tear under the weight against the studs I would assume.
Is there a liquid applied roll on or any other materials that might work that I should look at? The engineer didn’t spec anything for this and is not helpful.
Thanks in advance.
Replies
So you have a roof/ceiling slab over a vault or storage area that will be exposed on its top to exterior conditions. I'm assuming this is in a area where Winter conditions will exist. Is there any attempt to insulation this space?
Waterproofing under the slab makes no sense as it actually will exacerbate the eventual deterioration of the concrete slab over time due to freeze-thaw cycles.
The engineer probably assumed the concrete slab to be waterproof. It could be if using the appropriate admixtures. This could be addressed by the concrete producer IF they have experience with this kind of application.
It would be best to waterproof above the slab. Concrete, no matter how well placed and consolidated, is still porous. The metal deck used to support the fresh somewhat fluid concrete is simply a form and does not contribute to the slab's strength. It will likely corrode over time anyway due to the inherent condensation that will form below the slab.
The slab needs a waterproof membrane on top, below whatever finish surface is applied for the patio. The finished slab and patio surface should be sloped to insure water will not pool anywhere on the top of either the slab or the patio finishes.
You can utilize ordinary concrete or you can enhance it with admixtures that will decrease its permeability to water. In either case, it will be better served by waterproofing above the slab and providing positive drainage.
Sounds like a question for an envelope consultant or a lawsuit waiting to happen.
try a waterproofing membrane like BASF MasterSeal 583 or Sika Liquid Applied Membrane. They adjust to irregular surfaces and penetrate around studs without tearing
Sika's product is designed for application to the top of the slab.
BASF's product is intended to be applied to the concrete in liquid form and not to the steel decking in advance of placing concrete
If the decking specified is intended to provide composite action with the concrete slab, installing any waterproofing between the two defeats the purpose resulting in a weaker structure, particularly when the steel deck provide flexural strength to the composite concrete-steel structure.
When waterproofing corrugated decking before pouring concrete, consider liquid-applied membranes. These membranes seal irregular surfaces and protect against water penetration. Be sure to verify compatibility with your deck's design and structural integrity before application. Proper preparation is key to ensuring waterproofing effectiveness and deck longevity.