Sill seal or no?

[juddspaintballs]

I'm about to start building my house. It's on a slab and I'm using 2x6 exterior walls. The retired builder helping me will want to use pressure treated sill plates without sill seal because that's what he's always done and it's allowed. I've considered putting sill seal under the PT sill plate anyways because it definitely won't hurt anything. I understand that I could even use non-PT for the sill plate in that case if I wanted. Here's my question, though: I'll be doing porcelain tile on the entire first floor (including garage)...won't that make contact with the sill plates still and wick moisture from the concrete through the mortar into the sill plate regardless of sill seal?

 

[Firebrick43]

I can not believe someone doesn't use sill seal this day and age. That is insane?

Your tile should not touch the sill plate. There should be a good gap around the perimeter of the tile that is covered with base board. You should never **** the tile directly against the wall regardless of the type of construction.

 

[juddspaintballs]

Ah, good point. I had forgotten about the order of construction. Even if I took it tight to the drywall, there would still be a 1/2" gap between tile and sill plate. That answers my question entirely!

And yes, I'm going to use a sill seal and PT anyways. The few dollars extra is costs is worth it.

 

[Zeke]

Drywall is 1/2" off floor. Possible to let thinset run to the bottom plate. Maybe avoid that.

 

[billconner]

I'm not positive but if this is a house as you say, I think code requires the sill sealer for energy.

 

[beemerphile]

And, sill sealers don't seal. At least the foam ones don't. I use it, but I use Prosoco or Zip LiquidFlash to seal it to the concrete and the sheathing on the outside. Helps immeasurably as a bug sealer. On my recent home build, I let the ants show me where I had a path in from the outside. I let them work for a week and where they made it through I re-sealed. It is amazing that when you thing you have it sealed they find a void tunnel to crawl through. When the ants finally had to go over the top plate to get in, I knew I had it.

Not using sill seal is senseless, but in my view, relying on it to do what it says is senseless as well. Belts 'n' suspenders. My house blew under 2 ACH50 on the blower door. The tech thought something was wrong with his fan.

 

[juddspaintballs]

I intend on using an asphalt based window tape or such to seal from the slab up and over the bottom of the sheathing. Since I'm on a slab, there's a fair amount of places where the sill plate will only be a few inches off the ground. I figure the window tape will help keep the bottom of the sheathing from getting wet from splash back.

 

[nadogail]

When my house was built in 1988, the plates were not sealed to the slab, the cost of pulling back the carpet and caulking the plates was hard to swallow.

We had been bothered by the exterior dust infiltrating under the plates and being trapped in the carpet.

 

[rayra]

Ah, good point. I had forgotten about the order of construction. Even if I took it tight to the drywall, there would still be a 1/2" gap between tile and sill plate. That answers my question entirely!

And yes, I'm going to use a sill seal and PT anyways. The few dollars extra is costs is worth it.

weird. Why would you think the drywall would stop moisture transmission, if that is your chief concern?

Besides which, the drywall usually is not in contact with the slab, for the selfsame wicking concern.

You should seal with something, just to keep the bugs out. if you have a moisture problem at the sill plate / slab level, you've done one or more of several other things wrong, anyway. Your exterior layers should be shedding any water past / below that join. And your slab surface should be well above grade or any likely water pooling / runoff issue.
Concern about an interior tile floor being affected by moisture at the sill is something that should be so far down the probability list that it shouldn't even be of any concern. And would reflect several design and construction errors.

Lastly, your experienced helper is not building or paying for HIS house build, it is YOURS. Ask him for inputs, reasons, explanations, get informed and make YOUR decisions and they are his to implement or quit.

 

[tjpavlov]

I use sill seal with a bead of acoustical sealant above and below it.

 

[beemerphile]

I use sill seal with a bead of acoustical sealant above and below it.

That stuff works but damn it's messy. I spec'ed it overhead to seal the ceiling drywall at the exterior perimeter. The sheet rockers were ready to lynch me. Not sure what you are using for an air seal layer, but bugs can still find a way in through gaps between the sill plate and the sheathing. @juddspaintballs it is hard to get good adhesion of tape to the edge of a slab but you can use a primer to help. I find one of the good liquid flashes to work better. This is what I did on the home I just finished. I did the air barrier at the ceiling differently (and I think better). I applied a bead of Zip LiquidFlash at the sill/slab interface. Then because of the overhang of my insulated sheathing, I used backer rod in the gap with Prosoco Gap and Joint filler over the top of it. Only above the air seal line (attic and roof decking) was I willing to use tape. You cannot pay too much attention to this detail at this stage of construction. There is no reasonable way to go back and improve it later. This house blew a 1.5 ACH50 with the blower door.

 

[gunguy]

"because that's what he's always done ...."

That type of answer always bugs me. To me, it is an indicator of someone who hasen't learned about newer materials and techniques and refuses to educate himself to stay current.

While some things may not change or are done/not done due to various reasons, he should be able to explain the "why" and back it up.

In this case while sill seal may not be required by code, remember code usually reflects minimum requirements.

He may be a heck of a builder but that type of answer would be a signal to me to ask a few more questions.

Am I over-thinking this?

Jim

 

[Mainiac Mat]

How much is a roll of sill seal? There's your answer.

 

[juddspaintballs]

@rayra - don't get so worked up. I know drywall sits up off of the floor and it will be. I was just saying, if I took the tile as far as to the same vertical plane as the drywall, it would still be 1/2" off of the sill plate. It won't be that tight to the sill plate anyways because there will still be a gap to cover with baseboard as well.

I said I was going to use a sill seal. The way @beemerphile showed looks like a solid option. My slab will be at 3" off of grade at the lowest point near the garage, which is close enough to the ground I'd like to better protect it from splash back.




@gunguy - he's retired. He actually had to go take the test again to get his license back just to help me with this house. We spoke this morning and we're going to do a sill seal and something like beemerphile suggested. Apparently, he did normally use sill seal on houses but not on commercial. I've only helped him with commercial.

 

[mike93lx]

A couple thick beads of sealant works well too. You can get special caulking nozzles from sashco that will lay a 2" bead. Makes it really easy to get great coverage

 

[juddspaintballs]

A couple thick beads of sealant works well too. You can get special caulking nozzles from sashco that will lay a 2" bead. Makes it really easy to get great coverage

Are you saying to use it as the sill sealer or as the seal between concrete and sheathing?

 

[mike93lx]

Are you saying to use it as the sill sealer or as the seal between concrete and sheathing?

At the sill. Are you overlapping sheathing into the concrete?

 

[juddspaintballs]

Unless my builder friend has any other ideas about it, no. It should be a little higher than the bottom of the sill plate. The concrete will be too close to the ground at the lowest point to want to get the sheathing any closer than it already will be.

 

[dcg9381]

This is what I used, it's a gasket.

 

[Zeke]

Unless my builder friend has any other ideas about it, no. It should be a little higher than the bottom of the sill plate. The concrete will be too close to the ground at the lowest point to want to get the sheathing any closer than it already will be.

Something wrong there. Sheathing should fully lap the plate for nailing. Used to be 6" min above grade but I have read the IRC changed that to 8.

 

[bb29510]

use the seal to keep bugs out, ants love little crawl holes

 

[Pexto]

I pray that acoustical sealant and antiseize never have a baby. Because if they do, it's going to be all over my forehead. And yours too.

 

[pcmeiners]

Considering air infiltration causes the highest heat loss in a home, foolish not to seal the plate.

 

[ludakris04]

I like the idea of that gasket rather than the foam.
Current home was built in 2012. stick on concrete basement. One day I was replacing the outside hose bib, in an unfinished part of the basement, got up on a ladder and I could see light coming in.... right between the concrete foundation, the foam strip, and the sill plate.

I have since been working my way around the outside of the house, removing/replacing the trim and using Zip Liquid Flashing to seal everything up. Its ridiculous the gaps I have found.

 

[NUTTSGT]

I used sill seal on the garage and they caulked the interior edge/corner where the sill plate sat on the block. It helped fill in any little imperfections from I block laying....no mason here.

Heck, I even went as far to seal up the top core of every block with spray foam before the sill seal and sill plate. There's the exception of the core filled block though.

 

[Monza Harry]

I didn't hear anyone mention vapour barrier, shouldn't the interior vapour barrier be continued around to the Tyvek? I would think it should be plate, sill plate gasket, then v. barrier, then accoustic seal, then concrete. [From top down.] Even PT on concrete will rot! I need to fix this on my garage presently. Harry

 

[beemerphile]

I didn't hear anyone mention vapour barrier, shouldn't the interior vapour barrier be continued around to the Tyvek? I would think it should be plate, sill plate gasket, then v. barrier, then accoustic seal, then concrete. [From top down.] Even PT on concrete will rot! I need to fix this on my garage presently. Harry

The reason PT on concrete rots is that people make saw cuts and then don't treat the raw edges with preservative.

 

[Monza Harry]

I routinely use endgrain preservative. Buy I had to move the building over as it was "legal non conforming" ok when built but my addition required it to be conforming so I have ledge that is near impossible to water proof and any wood near the ground will get wet just a matter of time to rot with wet wood, vapour barrier should help for an extended period of time, as well as air/insect sealing. Harry