seam sealing

**hangNyak** · 03-31-2012, 21:45

I set up my new diy cat tarp in the yard today. I used the Permatex flowable seam sealer that was recommended in another thread. I only sealed the outside, though. After about six hous of drying, we had a rain storm come through. I went out and got under the tarp. I noticed at one end, it was seeping inside. So, after the storm passed and the tarp dried, I seam sealed the underside of the seam. Is this ok? Are both sides normally supposed to be sealed or just one?

**angrysparrow** · 03-31-2012, 21:51

Sealing both is fine. No harm at all.

It is typical to seal the inside only, in most cases. That keeps the sealant hidden. If it weeps, it usually just means a pin-spot was missed.

**rip waverly** · 03-31-2012, 21:51

we haven't dried out for days,,, and my WL tadpole was put through its paces after sealing with SilNet, ---only on the underside of the ridge, & only on the outside on the wall pullouts. 26 hours of steady abuse.

no leaks.

i've heard of folks doing both, but when vendors like JRB and OES have done it for me, it was only done on 1 side.

**hangNyak** · 04-01-2012, 13:51

It seems I may have a new problem. The seam sealer is dry, but it appears that I'm able to flake it off. I going to take a wild guess that this is not normal. Im not sure what the fabric I got from Scott is coated with. The only reason I bought it, was because he was out of the black silnylon. This is what I wound up with.
http://www.diygearsupply.com/cgi-bin/shelf.cgi?numb=16

**DemostiX** · 04-01-2012, 17:23

Flaking is why you want something flowable, very thin, just to fill pinholes and cracks while NOT leaving a film strong enough to pull the fillings out if that redundant film on the surface does not adhere and gets pulled off.

Silicone being what it is, cohesion is lousy once it has cured. It is not a property of the new stuff that it etches the old layer to improve cohesion.

**sweetmusic** · 04-01-2012, 17:36

You seem to have purchased a fabric waterproofed with polyurethane, not silicone. The two materials need different types of sealants. The Permatex is good for silnylon, for PU fabrics try one of the McNett products for polyurethane, such as Seam Grip or Seam Sure Water Based Seam Sealer.

**hangNyak** · 04-01-2012, 18:07

Can I just peel off the silicone based sealer and apply the polyurethane?

**MAD777** · 04-01-2012, 17:35

This fabric is not silicone coated nylon (silnyon), it is polyurethane coated nylon (PU coated). Polyurethane takes a different seam sealer than does silnylon. The stuff you used is a silicone based product and is therefore not adhering to the polyurethane.

Here is what you need: http://www.mcnett.com/Aquaseal-Ureth...lant-P193.aspx