LumberJocks

What to do with cracks on recently finished slab table

  • Advertise with us

« back to Wood & Lumber forum

Forum topic by Rando posted 08-10-2015 12:30 PM 772 views 0 times favorited 10 replies Add to Favorites Watch
View Rando's profile

Rando

5 posts in 483 days


08-10-2015 12:30 PM

Hi everyone!
I’m a new member and total woodworking noob from the Philippines. I just finished an 8’ x 43” x 3 3/4” slab table out of Magkono (iron wood), mounted on stainless steel legs—no screws, just two 2 x .3/4” cross-boards of Tugas glued to the underside of the slab, acting as stoppers and heavy-duty “velcro” in 2 places on either side of the bases’ flat bar frame. The slab came with cracks—end-grain cracks, on the top, bottom, sides etc… I successfully filled the top and bottom ones by flooding it with liquid epoxy after “squaring” it off. The dams I created around it to hold the epoxy for the sides, however, failed so I resorted to brushing it on (constantly until it gelled), thinking it would seep into the cracks and set. It’s been about a week since installation and I’m noticing some the cracks on the ends, specifically those that I had simply brushed epoxy on, starting to open up. Some of the underside “fills” appear to be opening up too, albeit, not as severely. The top “fills”, including the edges, with the exception of one or two spots, seem to be holding up pretty well, though.

It’s humid here and it’s the rainy season so I undestand it may be adjusting to the drier inside air. My questions are:

1. Am I set to see more fills giving in and/or further progression of existing cracks?
2. What of the finer ones… are these set to open like the larger ones, pictured?
3. Granted it reaches EMC and I somehow figure out that it has, will it be necessary to stabilize and refill the cracks, deep, with epoxy?
4. in relation to the above question, would building a dam around the ends be sufficient to get epoxy deep into the cracks or do I have to stand it up on one end?
5. Should I be worried that the underside cracks are opening up and the top ones aren’t? I’m concerned there’s sagging going on, although, I can’t imagine how with the way the base is designed. Perhaps cupping?

Any advice you guys can give would be greatly appreciated.

Thanks!
Rando





10 replies so far

View bondogaposis's profile

bondogaposis

4022 posts in 1811 days


#1 posted 08-10-2015 12:52 PM

It looks like the slab wasn’t thoroughly dry before you started. There isn’t much you can do until it gives up all the moisture it is going to, might take a year of being indoors. Your cross boards glued to the under side are a problem as they won’t allow for wood movement, which you are surely experiencing. Cracks are going to form unless the wood can be allowed to shrink as it dries. I suggest you remove them and replace with cross boards that have slotted screw holes that will allow the slab to shrink as it dries.

-- Bondo Gaposis

View JoeinGa's profile

JoeinGa

7475 posts in 1467 days


#2 posted 08-10-2015 01:03 PM

3.75” thick is pretty darn THICK! Was this wood given enough time to fully dry? And did you seal the bottom as well as the top? If not, that may make it more susceptible to splitting and cracking, because the bottom will keep sucking that humidity up into it, causing swelling.

As far as the ends go, I dont see how you would be able to get epoxy deep enough into those cracks to fill unless you stand it on end. Simply using a constant back and forth brushing motion will not force enough epoxy into the cracks, because gravity will take over, pulling it downward.

That said, from the pictures, it look like a really NICE table. Is it a dining table, or a conference table?

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View JoeinGa's profile

JoeinGa

7475 posts in 1467 days


#3 posted 08-10-2015 01:04 PM

Oh, and WELCOME to LJs !!

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View Rando's profile

Rando

5 posts in 483 days


#4 posted 08-10-2015 11:06 PM

Thank you, Bondo. I really appreciate the help. Some follow up questions for you if you don’t mind…
1. Is there a way to tell how much more movement should I expect? Such as observing the filled-pre-existing cracks, by how much more of them are re-occuring or progressing or have stopped doing so?
2. I assume it is recommended that I not attempt to refill until it has settled… In which case, would bringing it out for a couple of days to re-do the epoxy fills be enough time to mess with the moisture content again?
3. On the cross boards, I thought this was might have been a good way to prevent large splits/breaks from occurring. Just to clarify your recommendation… Keep the same length/width/thickness boards, re-glued, with the addition slotted screw holes to allow for a little “flex”? If not, can I replace them with smaller blocks instead, as I would rather not drill and screw on the slab itself.
Thanks again!


It looks like the slab wasn t thoroughly dry before you started. There isn t much you can do until it gives up all the moisture it is going to, might take a year of being indoors. Your cross boards glued to the under side are a problem as they won t allow for wood movement, which you are surely experiencing. Cracks are going to form unless the wood can be allowed to shrink as it dries. I suggest you remove them and replace with cross boards that have slotted screw holes that will allow the slab to shrink as it dries.

- bondogaposis

View Rando's profile

Rando

5 posts in 483 days


#5 posted 08-10-2015 11:29 PM

Hi Joe, thanks for responding and for the compliment. It’s a dining table which is funny because it’s just me and the wife here. —until we start having kids, anyway. LOL!
It was much thicker, about 4 3/8 inches before we started. I cannot confirm it’s moisture content, though. Seemed really old and dry to me when I got it but then again, I had no way to confirm this. —First noob mistake. All I could tell was that it certainly didn’t dry “right” to begin with. I mean, all these cracks I’m showing now were present when I got it. On seal… the entire slab is finished in nothing but oil and wax and simply fine sanded to give it a nice silky smooth surface.
As for eventually filling the ends… How about creating a pocket to hold the epoxy? Would that be sufficient to pull it deep into the cracks? I’m thinking I could keep the pocket there until it gels and simply slice off the excess epoxy.


3.75” thick is pretty darn THICK! Was this wood given enough time to fully dry? And did you seal the bottom as well as the top? If not, that may make it more susceptible to splitting and cracking, because the bottom will keep sucking that humidity up into it, causing swelling.

As far as the ends go, I dont see how you would be able to get epoxy deep enough into those cracks to fill unless you stand it on end. Simply using a constant back and forth brushing motion will not force enough epoxy into the cracks, because gravity will take over, pulling it downward.

That said, from the pictures, it look like a really NICE table. Is it a dining table, or a conference table?

- JoeinGa


View JoeinGa's profile

JoeinGa

7475 posts in 1467 days


#6 posted 08-10-2015 11:35 PM

I think if you just make a pocket to “hold” the epoxy, there wont be anything to draw the epoxy INTO the crack. All the epoxy will do is sit in the pocket and none will go inside the void.

Standing on end will allow gravity to do it’s thing and at least SOME of the epoxy will flow down into the crack.

-- Perform A Random Act Of Kindness Today ... Pay It Forward

View Rando's profile

Rando

5 posts in 483 days


#7 posted 08-10-2015 11:38 PM

Thanks Joe! I’ll go ahead and do that, then. Perhaps I should have the first time around. Would that have held the cracks together or is there no stopping movement until it truly settles?

View jdh122's profile

jdh122

879 posts in 2278 days


#8 posted 08-11-2015 12:09 AM

The cross boards are probably the main reason for the cracks – or else they are going to cause much larger cracks to occur in the future. The top wants to shrink but can’t because of the cross pieces – except that the force of the shrinkage is huge so it shrinks anyway, hence the cracks.
If you decide to put slotted holes and screw the cross boards, don’t glue them on (the screws are used instead of glue). But better still, replace with blocks at each leg. These you can glue on with no worries (especially if you orient them in the same direction as the table top).

-- Jeremy, in the Acadian forests

View Rando's profile

Rando

5 posts in 483 days


#9 posted 08-11-2015 02:46 AM

Thanks JDH, I’ll get on it ASAP.

View mahdee's profile

mahdee

3547 posts in 1228 days


#10 posted 08-11-2015 03:56 PM

The cracks look very much like the ones on my 4” walnut desk slab that was sitting around for over 20 years. I doubt you will see those cracks get any bigger.

-- earthartandfoods.com

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com