# Glue for MDF crown molding?



## Sleeper (Mar 24, 2009)

A while back I cut some crown molding to finish a job that I started but never finished. I have a contractor from my home insurance co that’s fixing some water damage and he said he would install the molding after he painted, but now it doesn’t look like that’s going to happen because the workers don’t know anything about that an I’m not even sure if that contractor has this job.

So anyway, I’m going to have to finish it myself and I have a couple of splices to make. I bought some CA glue but it was bad so I took it back to Home depot and the whole lot is bad and they don’t have anything else. My wife has to go to Walmart and I was going to see if I can buy it there. 

So just in case they don’t have any CA glue with the activator, what other glue will work for a fast set?


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## danrush (Oct 16, 2017)

I'd apply a liberal amount of Titebond II to both pieces. It sets mdf pretty quickly. 

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## Steve Neul (Sep 2, 2011)

MDF is paper. Just use wood glue on the splice if you wish. How is the seams done? Are they just butted together or is it cut on a 45? If it's cut on a 45 glue would bond to it alright. Most of the rest of us would just nail the molding up with nothing in the seam and paint it. Rarely is there enough movement in a house a seam will move and show.


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## NoThankyou (Mar 21, 2018)

I spliced it at 45°, used TB-III and shot nails through both pieces into the top of the wall. TB-II should work as well. after the glue hardens and dries a bit of sanding with 120 grit wrapped around your finger does wonders. 

Just remember that crown molding is CONSTRUCTION and not woodworking.

For filling the nail holes, use some soft wood filler and make the nail holes slightly concave. No sanding necessary if you wipe the excess filler off and they will disappear after painting.


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## Sleeper (Mar 24, 2009)

Steve Neul said:


> MDF is paper. Just use wood glue on the splice if you wish. How is the seams done? Are they just butted together or is it cut on a 45? If it's cut on a 45 glue would bond to it alright. Most of the rest of us would just nail the molding up with nothing in the seam and paint it. Rarely is there enough movement in a house a seam will move and show.


I cut them at a 45 to give me the most surface area. My problem with wood glue is that I can't wait until it dries. I need to bond immediately.
My walls and ceilings are not flat so I want the joint solid before nailing and then I'll fill in space between the wall and the molding with caulking


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## Steve Neul (Sep 2, 2011)

Sleeper said:


> I cut them at a 45 to give me the most surface area. My problem with wood glue is that I can't wait until it dries. I need to bond immediately.
> My walls and ceilings are not flat so I want the joint solid before nailing and then I'll fill in space between the wall and the molding with caulking


You can glue the molding together with wood glue before you put it up. It will hold nearly as strong as if it were one piece of molding.


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## shoot summ (Feb 21, 2014)

Steve Neul said:


> You can glue the molding together with wood glue before you put it up. It will hold nearly as strong as if it were one piece of molding.


Depends on the length, there is a lot of stress on longer pieces, I tend to use a 1/4" scab plate to help if for some reason I need to glue it prior to install.

I prefer to glue it in place if I can instead.


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## Steve Neul (Sep 2, 2011)

shoot summ said:


> Depends on the length, there is a lot of stress on longer pieces, I tend to use a 1/4" scab plate to help if for some reason I need to glue it prior to install.
> 
> I prefer to glue it in place if I can instead.


Yes, something to re-enforce the back would help however I've broken 12' pieces of crown trying to put it up by myself even without any seams. If it's very long it's really a two or three person job to get long pieces in place.


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## shoot summ (Feb 21, 2014)

Steve Neul said:


> Yes, something to re-enforce the back would help however I've broken 12' pieces of crown trying to put it up by myself even without any seams. If it's very long it's really a two or three person job to get long pieces in place.


I've been using these, they work OK...

https://www.amazon.com/gp/product/B001V9KFVI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


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## Sleeper (Mar 24, 2009)

shoot summ said:


> I've been using these, they work OK...
> 
> https://www.amazon.com/gp/product/B001V9KFVI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1


Oh I forgot about those. I was going to order them and just forgot. :wallbash:


Anyway, I bought some DAP RapidFuse All-Purpose Adhesive and I hope it works for my glue joint.


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## TimPa (Jan 27, 2010)

I have installed much crown moulding, and these are my tips for mdf.


I go around and place a small piece of painters tape over each stud, so you know where to nail. smaller crowns can be nailed into the top plate, but that tales a long nail.


45 deg bevel on the splices for sure. 


I cut the joint such that the piece overlapping the other is right over a stud about 1" before from the joint. that way you can nail the "top" piece well, and down hard over the joint. I don't nail through both, can split them.


dry fit before nailing. I place the flat against the wall a couple inches below the ceiling - then (keeping it flat against the wall) slide it up to touch the ceiling then nail.


you can pin up with pneumatic, but hand drive 8d finish will hold in place so much better.


I use painters putty for nail holes and any open joints, placed in with small screwdriver.


I like to install primed and painted crown. then a top coat over the nail putty.


coping - another discussion.
SORRY more than a glue answer - ignore at will!


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## Pineknot_86 (Feb 19, 2016)

I put up synthetic trim in the big bathroom. I used finish nails. If it is glued and needs to be removed, it will leave big holes in the sheetrock. The wife and I put up the trim. Easy to hold and nail in place. Don't have to hold it while glue sets.


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## 13579 (Jun 23, 2018)

Pineknot_86 said:


> I put up synthetic trim in the big bathroom. I used finish nails. If it is glued and needs to be removed, it will leave big holes in the sheetrock. The wife and I put up the trim. Easy to hold and nail in place. Don't have to hold it while glue sets.


I cut the joints for lengthing molding at compound 45 degree angle apply glass reinforced packing tape to the joint on the back after using tight bond like glue. Works well for me and never had a joint break or separate. Tom

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## Sleeper (Mar 24, 2009)

The glue I bought worked great however I'm probably going to have to remove it all because I don't have much to fasten it to. There doesn't seem to be any backing for the drywall except for the studs and nothing over the door ways. The drywall is so warped without being properly fastened down that there are huge gaps between the studs and the ceiling. I just don't know what its going to look like all that caulking filling in the gaps. There is one outside corner that has nothing to nail to almost like it was just a ceiling and someone set up partition walls without fastening them to anything except possibly the floor. 

I don't know who built this house but it is obvious they just wanted to get in and out to collect their money. One of the neighbors who was here since these places were built seems to think the used day workers because they heard instructions in Spanish to the workers like they had no idea of what they were doing.

Any I just don't have the time to deal with this because I got to get out of this house as soon as possible because it's costing me for utilities, insurance and taxes that I could use for something else.


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## Steve Neul (Sep 2, 2011)

Sleeper said:


> The glue I bought worked great however I'm probably going to have to remove it all because I don't have much to fasten it to. There doesn't seem to be any backing for the drywall except for the studs and nothing over the door ways. The drywall is so warped without being properly fastened down that there are huge gaps between the studs and the ceiling. I just don't know what its going to look like all that caulking filling in the gaps. There is one outside corner that has nothing to nail to almost like it was just a ceiling and someone set up partition walls without fastening them to anything except possibly the floor.
> 
> I don't know who built this house but it is obvious they just wanted to get in and out to collect their money. One of the neighbors who was here since these places were built seems to think the used day workers because they heard instructions in Spanish to the workers like they had no idea of what they were doing.
> 
> Any I just don't have the time to deal with this because I got to get out of this house as soon as possible because it's costing me for utilities, insurance and taxes that I could use for something else.


It sounds like at some time or another there has been a great deal of water in the house for the drywall to warp that much. 

Anyway try mashing the molding down and shoot your nails on a 45 or greater angle. Sometimes that will close up most of a gap. The angle sometimes will hold when there is nothing there but drywall.


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## Sleeper (Mar 24, 2009)

Steve Neul said:


> It sounds like at some time or another there has been a great deal of water in the house for the drywall to warp that much.
> 
> Anyway try mashing the molding down and shoot your nails on a 45 or greater angle. Sometimes that will close up most of a gap. The angle sometimes will hold when there is nothing there but drywall.


I don't know what happened, but its like some of the studs are bowed inward and others outward and they aren't exactly 16" OC, Plus the ceiling is not perpendicular to the walls. I removed some of the studs to put in a door and they looked really bad almost like they were used to drive a tract vehicle over them. They were cracked and split with a lot of bent over drywall nails.
My wife is determined to keep the crown molding and spent a good deal of time filling in with caulking and shes going to work on it again tomorrow. I told her if she can blend it all in with paint then we will keep it otherwise I'm pulling it out. There is one wall where the ceiling joist runs parallel and tight with the wall and I don't have anything to fasten to on top. I may have to run a 2x2 along the top of the wall fastened to the top plate for nailing to, but I'm going to wait to see if she can do anything with the other walls


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