Has anyone ever used self-made, eco-friendly sealing compound for outdoors?

  • What recipe?
  • How long does the recipe you used last?

I intend to use this sealing compound to stop wasps from getting in and out of my walls and removing styrofoam insulation (damn wasps) to build their nest.


  • The gaps are no more than 2 centimeters wide;
  • Environment is central Europe, not too warm, not too moist climate;
  • It is to fill the gaps between wood planks and concrete.

3 Answers 3


Indians, and later voyageurs used a mix of wood ash, spruce resin and lard.

Spruce resin is just collected off of trees. Melt. Once it flows well, filter the sticks and bugs out.

Add wood ash to the point where it is less sticky -- about the same volume as the spruce.

Add a bit of lard to keep it from cracking.

I don't think that spruce per se was requried. Pine, fir or larch probably would work just as well. Note that the the voyageurs carried a pot with them, along with spruce roots and rolls of bark for larger repairs. Birch bark canoes required frequent maintenance. This suggest to me that getting the right consistency to not be brittle in cold water, and not be to soft in hot weather was tricky. Mind you, a canoe has a lot more flexing than a house.

I don't have a recipe off hand. The drier (harder) the pitch is, the more lard you will need. Too little, and it cracks. Too much then on a warm day it flows out of the seam.

For a stationary application like this, I wouldn't worry about the lard.

I would try other fillers too. drywall powder should work. If the cracks are large, try adding a measure of unground wheat bran, or oat husks.

Another alternative is builder's lime. There is a long tradition of lime plasters. While lime is a high energy product, it's not as energy intensive as concrete (by about a factor of 4) Lime/sand plasters take a LOT longer to dry (weeks) but they are slightly flexible -- much more so than concrete.

  • Cracks are not large. I may try that one, but it will take a lot of time for me to gather enough spruce.
    – J. Chomel
    Apr 3, 2018 at 14:16
  • 2
    Pine resin should work. It's available on Amazon. Lard will go rancid. If you do need to soften the mix use a stiff grease or soft wax, it won't go rancid. Apr 3, 2018 at 15:01
  • This worked great, thanks! Easily found spruce resin here in the mountains. Don't by stuff on Amazon, they don't pay there taxes as they should.
    – J. Chomel
    May 13, 2020 at 8:07

To stop wasps, use metal window screen. (The plastic eventually decomposes.) Use a staple gun and simply cover gaps and holes. If you want a neater look, you can trip with some moulding or rough-sawn wood strips to match your decor.

  • Hi Jan, thank you for the idea. That's not exactly an answer to my question. And I cannot use stapling on the concrete wall (I should have been more accurate, apologizes)
    – J. Chomel
    Apr 3, 2018 at 14:18

Salt Dough

Another solution I used was to cover and fill the cracks with salt dough.

  • 2 cups all-purpose flour
  • 1 cup salt
  • apply and let it dry on a sunny day

Easier to implement than spruce resin with ashes, but could not live through the second winter (since it received too much rain this time).

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