Scarifying Concrete for drainage
Scarifying Concrete for drainage
(OP)
Considering options for placing a timber deck on top of a concrete slab on a single lane, one span bridge. I am concerned that water will collect between the timber and concrete and rot the wood decking too quickly. I am considering scarifying the top of the deck as a way to drain the water from beneath the decking but either need to slope the entire deck or vary the depth of the scarfs to permit drainage to one side.
Sloping the entire deck isn't desireable but I am not sure if it is possible to scarify concrete at a variable depth from one side of the bridge to the other.
Does anyone have experience actually doing this in the field to konw if this is possible?
Sloping the entire deck isn't desireable but I am not sure if it is possible to scarify concrete at a variable depth from one side of the bridge to the other.
Does anyone have experience actually doing this in the field to konw if this is possible?






RE: Scarifying Concrete for drainage
The deck should already have a 2% slope towards one or both sides. If so, it's probably easier to groove the bottoms of the timbers. Any carpenter with a router would be able to do that.
Most decks are grooved or tined to allow water to displace outward or lengthwise out from underneath car tires. NY has switched to longitudinal grooving, since it supposedly works as well and is quieter, but you may be able to find a contractor in your area that can still do transverse grooving.
Grooving a 1/4" or so shouldn't make much difference, but you should probably check the record plans to make sure you'll have enough cover over your rebar after grooving.
"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928
RE: Scarifying Concrete for drainage
One of the problems I've seen with timber decks, particularly thicker sections, is that rot occurs through the center of the member, appearing to leave the exterior intact. That, of course, was not on applications like yours, but does show that timber can deteriorate in different ways.
For your application, you might consider an asphalt coating on the bottom of the timber materials, if you have no other choice and cannot otherwise isolate the timber from the concrete. Keep the kerfs with the kerf bottom sloped to drain.
RE: Scarifying Concrete for drainage
In any case, I think scarifying the deck with a slight slope in addition to using an ashpalt coating on the timber is a decent approach.
I also wonder if using a drainage panel, such as is done with exterior plaza or green roofs might help keep moisture away from the decking. Any thoughts on this approach?
RE: Scarifying Concrete for drainage
It doesn't rot alot and it you get the recycled kind someone may be able to clame it for points towards some enviromental do-good award.
RE: Scarifying Concrete for drainage
The concern would be the type and amount of occasional traffic from vehicles, this type of decking is only 1-1/4" or something similar off the top of my head...
RE: Scarifying Concrete for drainage
Not knowing what the geometry is, couldn't you just build a timber deck from the beginning? Are you worried about tracked vehicles beating it up? You could build your deck, then ledger-lok 3" plank to it for the duration of construction, then remove the plank. Think wetland mats for heavy equipment access.
RE: Scarifying Concrete for drainage
RE: Scarifying Concrete for drainage
I have considered a composite or FRP decking, perhaps even a two-layer deck where the lower layer is the FRP and the upper layer is a heavy timber (timber was a specification from the owner).
Any vehicles on the bridge after the initial construction phase would be an occasional maitenance vehicle or emergency vehicle. For that reason, I am not totally concerned with them damaging the decking with traffic.
VTEIT, that is a great point, thank you for your tip.