Best glue to attach walls with a dado joint to the floor?

[Esteban]

I'm almost ready to attach the sandwich walls to the floor. The walls have Dado Joints as illustrated above. I'm wondering what would be the best "glue" to use? Glue, adhesive, or epoxy? The outside plywood wall skins are fiberglassed (fiberglass cloth and epoxy) and will be painted.

I'm considering using thickened epoxy for it's bonding strength and waterproofing characteristics. A caulk gun with a good construction adhesive might do as well and be easier to use.

Ron Dickey and I recently test fitted the walls to the floor. They fit too snugly. One wall leaned outward and was very hard to pull up straight. I sanded the dadoes and floor so they both should fit better now.

This weekend I'll make "dead men" to hold the walls up straight. After months and months of work to get here this is a (nervous) step I want to be sure to get right.

[starleen2]

I'm thinking something like PL adhesive or exterior liquid nail - I may give you more open time than epoxy?

[planovet]

I used epoxy when I glued my walls to the floor. I wanted to make sure it held very well.

[Esteban]

Is it helpful to use fasteners (screws, nails, staples) too? Or just adhesive, or epoxy, and clamps.

If I use epoxy I'm considering first brushing the dado and floor edges with epoxy mixed with a slow hardener to let it soak into the wood. After that I'd use epoxy thickened to a mayonnaise consistency with fumed silica (cabosil or aerosil) to ensure a good, void filling, "glue" bond between the walls and the floor.

[doug hodder]

Steve...I'd think that if you have done all this other glass work and used epoxy, why not use it to attach the walls with. It'll give you plenty of working time. I put them up by myself and have plenty of time to adjust and secure them. Just get your jigs, clamps, rests etc....all set before you butter it up with epoxy. The thickened stuff will work fine, I usually secure the wall bottom in place with screws. I don't see a real need to pre-coat it with the epoxy prior to the thickened stuff. Doug

[bbarry]

After that I'd use epoxy thickened to a mayonnaise consistency with fumed silica (cabosil or aerosil) to ensure a good, void filling, "glue" bond between the walls and the floor.

It works well to brush on a light coat of straight epoxy onto the pieces and then follow up with a thickened batch. This ensures that epoxy penetrates into the wood and you don't end up with a "dry" joint.

From what I've read (and my very limited experience), wood flour is what you want to use to thicken your epoxy when bonding two pieces together. It cures hard as nails (and is a real $%$!@ to sand). Silica or phenolic agents appear to result in a much weaker bond, but they sand up nicely.

Also from my limited experience (so take with a grain of salt), I had better luck when I thickened to peanut butter consistancy. It was much less of a mess, didn't squeeze everywhere quite so bad.

Brad

[Esteban]

Thanks for the ideas. I'm feeling more confidant. Have decided to use epoxy to attach the walls to the floor. With reinforcing screws, too.

Here are the steps Raka suggests for gluing with epoxy. I bolded for emphasis.:

GLUING

Because of Epoxies strength and tremendous adhesive
power, users will often do quick and sloppy work and
maybe get away with it. I'll explain the correct method; if
you want to leave out some recommended steps, it’s your
project. The surface quality of your job may look fine, but
the ultimate bonding strength will not always be
immediately apparent. Murphy's law is ever present.

1. The surface to be bonded must be clean, dry and
free of contaminants.

2. Sand the surface with medium sandpaper to provide
tooth for the epoxy to grab on to.

3. Brush your mixed epoxy onto the bonding
surfaces. If you have time, allow it to soak in for a few
minutes and recoat.

4. Add your filler to the leftover mixed resin in your pot.
Silica is a good choice. Mix very thoroughly, making sure
all the stuck together balls of silica are completely
broken up. The past does not have to be very thick.
Apply the paste to your two pre-coated bonding surfaces.
When the two bonding pieces are pressed together the
paste just needs to be able to squish around and fill all the
voids. Adding too much filler may make the paste dry with
less sticking ability and less flexibility. If you try to glue
using only unthickened resin, it could all soak into the
wood or sun off, leaving a dry bong with a possible later
failure.

5. Very lightly press the parts to be bonded together, and
clamp loosely. It's to the epoxy's advantage not to all
pressed out of the bond.

6. Cleanup or use the epoxy squeezed out of the bond.
Remember, how you clean yup and do your final shaping
will save you a lot of sanding later.

7. When the curing epoxy can't be dented with your
thumbnail you may start to sand. Please be aware that the
final cure may only be 70% complete at this stage.

8. Be careful of the type of wood your are gluing as some
hardwoods that are dense or oily may require special
preparation. A clean surface, very course sanding and
having the epoxy warm or as thin as possible may be
required. Test and experiment before committing to a
large project.

I intend to follow Raka's steps 1 - 6 for attaching the walls to the floor. Yes, I've decided to use epoxy. I have a snug fit between the wall dadoes and the floor overhang. Don't think I want to try adding sawdust to the epoxy mixture because it might thicken it too much. A epoxy mixture thickened with silica should be strong and filling enough.

I'm going to add additional strength with screws from below thru the skirt into the floor overhang, and angled from above. It might be overkill to use screws too. It makes me more confident it'll hold well in the future.

Yesterday I made several deadman braces to hold the walls straight up as the epoxy sets.

I also used a Kreg pocket hole tool tool to drill pilot holes for reinforcing screws to secure the walls to the floor. Have 10 pilot holes coming straight up on roughly 1' centers through the 2" high skirt board to screw into the floor overhang. Inside the cabin doorway(s) and the galley I drilled 6 angled pilot holes to screw downward into the floor - both are areas that will later be covered with trim.

Almost ready to put the walls up permanently. Need to call on a friend or two to help me put the walls up sometime in the next few days. Off to the hardware store for supplies. When I go to the store maybe I should get some fizzy pop to thank (bribe) them for helping?

[Arne]

mine is kind of a combination. The inner wall hits the floor, the outer wall extends down to the bottom of the floor. The 'key' is glued/bolted through the floor....

if you go to the link below and look near the bottom of the home page, you can see the 'key' bolted to the floor, and how the wall fits over it. quite simple to do.