Asphalt repair for timber bridge decks

What is the existing wearing surface made of - lumber? Or an existing asphaltic course? I haven't done one, so I have no experience to draw on. But I'd be concerned about trapping moisture beneath the asphalt, resulting in an acceleration of rot. And my concern isn't reduced by the wood's exposure on the underside of the bridge...

I think the geotextile idea itself is good - it should reduce cracking of the asphalt and increase the life of the wearing surface.

Let us know what you decide to do.

Don't forget to check the weight of all that AC
I'd use 140 lb/CF.

The rotting previously suggested is a true concern.

Is the timber deck a single layer? Often that top surface is in 2 layers.

Is the deck going to drain OK?

Ussually the deck is two layers, creosote impregnated timbers.. We tore down a timber bridge in Mpls that was 80 years old. It had 4" of asphalt on it. The timbers were recycled into 'swamp pads' for excavators. No rot.

I worked on a township bridge, mail ordered from the Milwuakee Bridge & Iron Co. in 1864 (No, I wasn't around then)that had a wood deck with many layers of asphalt paveing. Back then the bridges were sent out "tinker toy" style on a train or horse drawn wagons and erected on the site.

The township wanted to preserve the wrought iron truss, but was concerned about the weight limit. So, we ended up putting a new steel grid deck on the bridge, it was half the weight of the timber and ashpalt. That might be a solution for you to think about.

One thing to keep in mind, steel grid decks can be pretty slippery in the rain or snow, so post a low speed limit for the bridge.