Seam sealing a tent

The newly arrived Lightheart Gear Solong 6 that I wrote about recently, needed some seam sealing. So I took the opportunity of doing that one sunny Sunday. Seam sealing is really pretty easy, once you know how.

By Jörgen Johansson

First some basics. Most tents for outdoor use these days have their rain fly made from siliconized nylon. Popularly called silnylon. Lightweight tents usually also have their floors made from silnylon, while some sturdier and not extremely lightweight tents use polyurethan (PU) treated floors. What I am writing about here goes for silnylon, not PU.

First, let me say that for the first 30 years or so of my outdoor life I happily used tents without seam sealing them. And they never leaked in the seams. Truly. Seam sealing in my book has arrived with American lightweight tents and probably also with really lightweight silnylon materials. So nowadays I habitually seam seal my tents, it is easy to do and a leakage could be potentially uncomfortable.

There are number of commercial seam sealants that I have used, but I see no real reason not to use something simpler and cheaper. I use ordinary bathroom silicone that you can pick up at any builders store. Unless you plan to use it for actually sealing things in a bathroom there are much smaller containers to be bought than the one in the photo.

Brush, empty yoghurt container, white spirits and silicone.

This silicone (as well as the commercial varieties aimed at seam sealing tents) need to be mixed with a solvent to approximately the consistency of olive oil or slightly thicker. Otherwise the penetration into the seams will not be as good and it will leave unnecessarily thick trails on the seams.

I have used both white spirits and petroleum ether as solvent. White spririts is not so volatile/quick drying and thus easier to work with, especially on bigger surfaces. That is what I recommend. The petroleum ether dries in seconds.

For the Solong 6 tent I put a strand of silicone, about equal to the amount of mustard you would put on a sausage. I mixed this with a bit of white spirits and then a little bit more until I had the consistency that I wanted. That was enough for the seams on the Solong 6.

After that it is just a matter of applying this solution to the seams with the stiff, shortened brush. I try to work the goey stuff into the seam as I go along. Places with loops for hanging inner tents or fly doors or whatever get some special care. They are always week spots, that is were I have had some dripping on rainy days and nights.

Work the olive oil thick solution into the seams with a stiff, short brush.

After finishing one seam I take a piece of cloth or some paper tissue and wipe off the excess silicone. Then I leave the tent to dry outside for a couple of hours. I do not think it really matters if it rains a bit on the tent during this time. Often I leave the tent hanging freely inside for a couple of days.

All this to ensure that excess silicone somewhere will not stick to the walls if you roll the tent into its stuff bag. That is NOT fun and could cause a lot of damage if done too soon. Sometimes I use some talcum powder on the seams to ensure that this does not happen. This is an alternative if you do not have a garage or some other spacious area.

You can use the same method for waterproofing worn silicone tent floors or the entire fly for that matter. Then you have to have a good size, soft painters brush to cover a big area uniformly.