how much weight can I expect seam-sealing adds to a shelter’s weight?

Unless you really slop it on, it should add no more than an ounce to the weight. What does add weight is painting "non-skid" stripes on the silnylon floor. I added nearly 2 oz doing this to my SMD Luna Solo. I may have overdone the non-skid part though.

My first silnylon tent was a Tarptent Squall II. I went a bit overboard and put 2 oz. of seam sealer on it.

Since then I've seam sealed a Tarptent Rainshadow II, a SMD Lunar Solo, a GG/Tarptent Squall Classic and a ZPacks Hexamid Twin. 1 oz. added for each, including floor spots (instead of stripes) on all but the last. Hint: on the floor stuff, to keep pad from sliding you don't need to paint the floor at the bottom end, the top end or right next to the sides. Only put the sealant where your pad will hit! Spots are easier to clean around than stripes. Especially don't paint too close to the door, because that's where the most dirt will stick to the sealant!

When I sealed my TT Rainbow and added floor strips it added 1.2 oz. – but with floor dots that could be less (I also do all the seam lines 2 times)

Evidently, I slopped sealant onto my Tarptent Notch– between the seam sealing and anti-slippage stripes, I added 2.1 oz.

I do most TTs with under 1oz of silicone.
My preference is for a very diluted version so that it soaks into the stitches.
A bit of a fine line between thin and too thin but essentially you don't want blobs nor drips running off the stitch line..
I used to stripe/dot the floor with a fairly heavy mix now I dilute that well also because it appears that a thin layer does a good enough job.

BTW, when seam sealing make sure you do the base of these Velcro/ribbon/elastic bits that stick out from the fly :

I had an unfinished DR set up when it started to rain. The next morning the floor had several drops , at first they appeared random then realised they corresponded to those four not yet sealed loops on the canopy.
(the wind had spread the spray around…)

I think I went wrong with not diluting the scilicone sealant :(…now I have to look elsewhere to find a bit more weight savings.

This is a random section of a sealed seam of my Notch :

I know many don't dilute but this may give you an idea of why I do.

measure the weight of the tube of seam seal before and after … that will tell you

but the real answer … not enough for you to notice in any way, shape or form … except through a digital scale …. in other words it wont matter ;)

You have to weigh tent before and after because some of it evaporates

Except, you're right it won't really matter

@franco – that is some GOOD LOOKING seam seal – kudos!

btw – if i am using seam GRIP (eg on eVent, Pertex Sheild etc) what would you dilute it with?
Mike

When I was doing the BD and Bibler shelters I used the provided Seam Grip squirting it onto the seam with a syringe.
It is possible that I diluted some with Shellite (white spirit/Coleman fuel) but maybe that is what I was using then to dilute silicone, not sure.
The last time I used Seam Grip I think was about 7-8 years ago…

Franco that is some sick seam sealing man….you've been practising haven't you? :)

…..mine doesn't look like that at all.

Anyway of removing seam sealing???…and starting again?

Not worth it in my oppinion.
I have seen comments about the sealing peeling off, I just think that the wrong sealant was used , if that happens you can try scraping it off but it is a messy job.
A mate of mine (sells tent in a local shop…) did a tarp with the wrong sealant and that started to peel not long after, I scraped some off with a toothbrush and a blade and then did the other side for him.

I use Henry's approach and use a small foam brush. 3 or 4:1 ratio of mixture. The only way I can tell I have any sealer on is by touch.

Added 1.2 oz to the Notch and that is with painting the floor with slip stripes as well.

zero

I never seal the seams on my silnylon tents and never noticed any leakage

In Oregon I get a lot of testing

I have pyramid tent that has seams at steep angle so that helps

you might want to try your tent and not seal it until you notice it leaking

I sew on these velcro strips to keep door open, and I've noticed them to leak, so I seal them.

Oh why did I not dilute?????? Or just paid TarpTent to seam seal for me(probably you Franco would have done the job then for them)??????

Lesson learned. Though wish I would have learned on a sh1tty tent and not on the Rainbow I got….I absolutely love this home away from home :)!!

I dilute silicone with odorless mineral spirits as per the video below.  I found it at an art supply store.  I know you’re not seam sealing but for that, I do it the Tarptent way.  I can barely see it on the seams when done.  In the video, he also paints some stripes on the floor of the tent.

Jer said

Zero … I never seal the seams on my silnylon tents and never noticed any leakage

In Oregon I get a lot of testing

I have pyramid tent that has seams at steep angle so that helps

Glad this thread was resurrected.  I’ve gotten ahold of a sil-nylon mid and nesting inner tent, so looking at ways to minimize the seal sealing.

warning, I may be in the minority on this.  Probably most people seal their seams?

I have still never sealed my seams and never seen any leaks

I’ve seam sealed them, but looking to lightly reapply (put a light second coat) after taking off my first hack … er, field expedient job by careful peeling and with some mineral spirits.

Just looking to keep the next application minimal.

does it ever leak when it’s rainy?