Hello there, i have a building company in cyprus and I am using mgo boards for the interior walls. We are very pleased with the characteristics of the material, however we have experience the formation of some cracks along the connection points of boards.We believe it is due to the hot(temperature :10 to 45 C) and humid climate and perhaps the unsuitability of the materials used.

Does anyone else experience the same problem?What is the most suitable material to be used for the joins of boards?

Thanks in advance.
Chris Kagias

Sorry to hear you are having any kind of problem. Can you tell us what method and materials you used for your joints. Most manufacturers I have worked with in the design of joint compounds and joint systems have a very good record of NO problems with joints. MGO board has almost zero thermal movement so is probably not the cause of this issue.

Thank you for your response I built houses using MgO boards [partition walls].I used metal frames the same are used for gypsum wallboards.
I leave 3mm spase between the boards
We putt elastic putty in the seam.
c. We leave to dry.
d. We use self-adhesive net tape to cover the line of the
seam.
e. We coat the tape 15 cm left and right from the line of
the seam using elastic putty.
f. We leave it to dry enough and i make an other coat using more smooth plasterig putty the finish
g. Then we paint the wall.
Some times we made all the wall plastering using acrylic
coat .
At the end we had the same result cracks along the connection points of the boards.
NOTE: we use many materials to give solution without result.[I used polymer waterproofing plaster glue.these matterials are used forICF plastering.I used all the kinds of compounds where we are used for gypsum boards, i used many elastic adhesives:KIMIA BETNFIX RS,MAPEITHERM AR1,MAPEI PLANITOP100,PCI NANOLIGHT,JUPITOL,GOLD BOND JOINT COMPOUND etc.
I made one wall 9 m x3metres and i test all these materials without result i belive that i tested about 50 materials
I am very disappointed.

Thanks in advance

Chris Kagias

Were the screws countersunk?

What happens if you use no space between boards?

Seems like a very odd problem. Can't imagine what would be the cause. I think to confirm that the problem is related to the MgO board you may need to do tests with both MgO and regular sheetrock (gypsum). If you experience problems on both test subjects then it is either a problem with the joint products, installation, or environmental or some combination of all three. If the problem only occurs on the MgO test subject then I think you can conclude that one or all of the above are incompatible with MgO board.

Does your supplier of the board have no suggestions? Would think they would be anxious to help you in order to promote the product in your area.

Instead of the mesh tape joint reinforcing, I would adhesively bond a continuous 2" strip of light guage corrosion resistant sheet metal over the joint and then apply plaster over that. You need heavy duty joint reinforcement to control the thermal expansion.

I think a 'Urethane' based glue would do the trick. In the US a brand of glue readily available in the hardware store would be 'Gorilla Glue', but a generic brand would probably work too. Make sure the surface is flush/smooth, and the fastener heads are not sticking up.

Dear All

Thank you for your advice. I would like to confirm that we have tried a range of screws, we have connected the boards together but in both cases the problem persists. We have tried gypsum boards successful so we believe the issue only appears on MgO boards.

From what we see cracks appear only when the temperature increases beyond 93F (34 C°), humidity seems to make things worse. When the temperature goes down (early morning hours) magically the cracks disappear!

Recently we have tried glass-tape over the joints and it worked well. The house where we tested the glass-tape presented no cracks while others closely located had cracks. I am not exactly sure as to why this worked and whether is going to be persistent in the future.

Has anyone seen this before? Any ideas what will be the root of our problem? Any other materials which will be suitable to use?

We will also experiment with urethane based glue per SimonD’s advice and revert.

Thanks for the help

We use non-recessed MGO Board and DAP ElastoPatch Flexible patching compound to patch the joints between the boards. Most MGO board is pre-sanded so cleaning the dust from the surface of the board at the joint is important to ensure a good bond. Wipe the MGO board with a clean damp cloth to remove any dust. Allow to dry. We use fiberglass self stick tap. Then spread the first coat of compound very thin, just enough to cover the tape. We only spread the compound about 1/2" wider than the tape. Sand and coat again with another coat of compound. You should be good to sand and paint without the need for a third coat.

Posted By Innova on 01 Jul 2014 02:35 PM
We use non-recessed MGO Board and DAP ElastoPatch Flexible patching compound to patch the joints between the boards. Most MGO board is pre-sanded so cleaning the dust from the surface of the board at the joint is important to ensure a good bond. Wipe the MGO board with a clean damp cloth to remove any dust. Allow to dry. We use fiberglass self stick tap. Then spread the first coat of compound very thin, just enough to cover the tape. We only spread the compound about 1/2" wider than the tape. Sand and coat again with another coat of compound. You should be good to sand and paint without the need for a third coat.

That all sounds great in a perfect world, however the least little variation at the joint will force you to "feather" the joint
By the way .............DAP Elasto Patch is an elastomeric product (similar to trowel-able caulk) it is not sandable?

Innova supplied 6 buckets of this elastic patch material for my 1700 ft2 project, for which they helped themselves to $500 of my money. This was sufficient for one room. The material they provided was the wrong type ("textured" not smooth) and the tape they provided was very fine non-stick tape that blew around like toilet paper. The roof panels bowed badly leaving steps between the panel joints requiring feathering as Kavala states. Finally, there is a conflict between the instructions provided by Innova (ie to sand the patch) and the label on the product which states it's not sandable.

what kind of edge do you have for mgo board? square edge? tapered edge?

Hello, I am located on the coast of Ecuador, and have build a building with 4 townhomes, using MGO boards, the building is nearly finished, however the outside wall keeps having problems at the seams, Interior is fine, we used a something called, Muro Seco in the gap between the panels, then a sealing paint, then a flexible paint. Two month later all the material in the seams are bulging out! So we used a disk sander to remove all the material. So we started at square one! Now we are applying a mixture of Resin and a Powder, (sorry don't know the English word for it), it makes a paste, however it hardens very fast, so can only apply a little at the time. After that we sanded the area to make it smooth, and applied flexible paint. The results have been good sofar! Fingers crossed!