Waterproof sewing fabric

[Idaboy]

If sewing a non PU,membrane fabric (something like 500d or 1000d cordura) but want to add some water resistance, has anyone put polyurethane ( like you would to a tent floor or seem), just a thin layer? The fabric is just going to be knee patches and a seat patch, the intent is not to make the pants all waterproof but rather these reinforced pressure points less likely to soak through if sitting/kneeling on damp ground.

 

[Bachto]

This may work for awhile. I would be worried it would wear away since those are high wear spots. You may be having to reapply every so often.

 

[Thinkingman]

Your idea is pretty interesting.
I would coat the inside of the Cordura (the face that will be against the pants and away from ground contact) and your only wear would be from friction between the patch and the pants fabric.
Let us know if you pursue this.
Further thought....You will probably eliminate any breathability in those areas....Not that the tradeoff isn't worth it.....

 

[nodakian]

Is adding a layer of XPac rather than a coating an option?

 

[roosterdown]

Because I don't sew very well I often coat my seams with seamgrip. I would think your idea is fine, but you'd want to work the sealer into the fabric well...