An Airtight Home: How to Choose and Install Sill Sealer Gasket
**Our honesty policy: This post may contain affiliate links and I may be compensated if you make a purchase at no extra cost to you. Some are, some aren't--I do some comparison shopping. The important thing is you will know exactly what we are talking about. Drop a note/comment if you have any questions on the products as these are materials and tools we use on our own projects.
Plain polyethylene foam sill sealer on a new construction neighborhood jobsite.
Normally homes are built with a familiar pink polyethylene foam type sill sealer. However, there are definitely new products on the market vastly improving the effectiveness of a sill seal.
Just in case you are unfamiliar with the reason why this is so important when framing/reframing some portion of your house here is a quick lesson. Framing is more than just the base plate, studs, and top plate. There has to be some kind of barrier between the sill plate and the concrete below, otherwise, the the wooden sill plate is in contact with the concrete slab foundation. We know concrete is porous and has the property of wicking water. For instance, the edge of the foundation soaks up some water when it rains or if there is sprinkler overspray. A sill sealer is a capillary break between concrete and the bottom plate, keeping the wood from getting wet and rotting away. If the sill sealer product is good enough, such as the structural gasket mentioned below, it also acts as an air break, preventing air, moisture, dust, and insects from entering. The goal is to improve the air quality inside your home.
As you can see there was more than a little rot in the base plate as well as the studs. This was all hidden between the exterior siding and the interior drywall. There is no doubt any sill seal at all, including polyethylene foam, would have slowed the rotting process down. A structural gasket would have been even better.
My husband is currently reframing parts of my aunt’s home as well as her garage. With these fixes we had the opportunity to use one of the best sill sealer gaskets on the market: a structural gasket from Conservation Technology.
As you can see from this end, the integrated triangle design and rubberized material are the beauty behind using this product.
As much as a slab of concrete looks flat, it is not. There are little disparities: unnoticeable dips and bumps over the long distances as well as little nicks and chunks from when the slab was poured. Likewise, the base plate wood is not 100% flat. It also has little variances from the growth circles as well as if it is true. Both of these together can cause little gaps in your home at the base plate.
Profile of plain, polyethylene sill sealer with no ridges used on a new construction job site.
The triangles on either side of the structural gasket are what really seal off any space between the concrete from the wood. The triangular design on both sides fill in any gaps or holes. Compare this design against the regular flat polyethylene sill seal. Yes, the pink polyethylene foam has small ridges running lengthwise. Some do not have any ridges, as pictured (this is the product used in the new neighborhood under construction next to my neighborhood). However, in comparison, the soft rubber gasket triangle really seals off everything with the size of the triangular design and long lasting give of the EPDM rubber material.
These gaps can allow uninvited guests as well as weather into to your home. Walls flex with weather and gaps allow outside air as well as dust and difference in temperature into your walls and possibly into the interior. The give of the EPDM flexes with the changes in temperature, pressure, and keeps these elements from making their way inside.
As for my aunt’s home–the old 2” x 4” garage framing is now constructed with very solid 2” x 6” framing. This framing is protected by this structural sill seal gasket along the base plate.
How to install sill sealer gasket
It goes on just as any other kind of sill sealer. First you clean off the surface where the old framing went: both the residue and any other loose debris.
A picture of the concrete before cleaning off the residue and debris under the last base plate.
Here is a picture of the clean concrete taken the opposite direct of the previous photo.
Sweeping and scraping off the area gives the structural gasket a perfectly clean surface. It will also keep the sill sealer flat against the surface on the ground, properly sealing off the base plate.
Next, lay the base plate upside down. Lay out the structural gasket with the flat part against the wood and the triangular pieces of the structural gasket facing up.
Once in place, staple the gasket to the base plate.
Then flip it over and continue framing.
Once the framing goes into place, then it is bolted into the flooring tightening down the seal against the floor.
Here we’re looking at the inside of the wall before it is has supporting studs on top and bolted down to the cement.
Now we’re looking at the exterior vantage point with the studs and bolts (the little red piece on the upper right) in place.
As you can see even though it’s tight against the floor there still a little bit of gap between the concrete and base plate from the seal. You still finish off the sill seal with caulking on the interior side and some kind of glue and stick or peel and stick tape on the outside.
Difference in price
Despite the fact this kind of sill seal has been around for quite some time in Europe, structural gaskets of any sort are not readily available at your local big box store…yet. Here is where you can call and order it.
A 50 foot length of 5 inch wide polyethylene foam type sill seal runs about $9.50. A 75 foot roll of 5 inch wide EPDM structural gasket runs $60 plus shipping.*
It is more expensive, but the quality of product is much higher. You are not just paying for a capillary break. You are paying for air quality, less heat transfer, and protecting your walls literally from the ground up. As building codes become stricter these small changes will become more common as well.
The sill sealer structural gasket offered by Conservation Technology is just another example of how building science is making advances. Our homes are getting better sealed against outside elements and air quality inside is improving. Installing sill sealer gasket is certainly worth considering for your next framing project.
We ran a set of tests to test the durability of EPDM and polyethylene sill seal gaskets. Check this post for the results!
*Please don’t shoot the messenger if prices change. These are current prices as of 5/27/2018.
Oh MY. Harvey. The gift that just keeps on giving. On a happy note, that garage is going to be sturdier than many 3rd world mansions. Well, SOME of that discovery was because of Harvey.
Yes, Harvey–a six letter curse word around these parts.
It certainly is one of the best garages around. A couple more garages and homes down the street and in the greater Houston area will soon have this product too!