Mortar not sticking

[blacknoir]

I hate to ask this but here goes. Some of my bricks have a tendency to come undone after a day.. an example is my arch.. it looked good but I bumped it while working and it shifted. I looked closer and there were a few connections that weren't sticking. It's an arch so it stays up but I'd prefer it stick together more.. I've also had bricks come loose on me... Do I just need to be patient and wait a few more days for them to firm up or are the ruined now that they've come loose? I've slabbed on more mortar where I've seen some come loose but I worry about that arch.

I've worked with thinset before and that stuff stays stuck.. but that's inside where the temp and moisture is fairly even.

The first time this happened was the day after I had setup my soldiers. I bumped one while setting up to do the next row and a whole section of soldiers moved. The section seemed rock solid but it still came away cleanly between 2 bricks. I checked the rest of the soldiers and there were a few breaks like this. That time I shaved off the old mortar and put new mortar on. I really don't want to have to rebuild the arch since I've already started putting chains against it.

[dmun]

Re: Mortar not sticking

Mortar doesn't reach anything like full strength for a week or so. Keep all new masonry moist, and avoid shocks and stress for a week, and you should be all right.

You wet your brick before laying them, right? Dry bricks can cause the non-adhesion you're talking about.

[blacknoir]

Re: Mortar not sticking

Oh yeah, my bricks sit in water for at least over night.. I also wet any dry areas before adding bricks to them. I'll just leave them and hope for the best.

[timo]

Re: Mortar not sticking

I am working with the home brew mortar and can say that it takes about 4 days to get hard.

On the other hand, between the sun and air, it sets in a few minutes. I am constantly soaking bricks and spraying the next course for the next brick.

What mortar are you using?

[pizza_bob]

Re: Mortar not sticking

I called the manufacturer of Heatstop 50, which is what I am using for my oven. I asked them if the firebricks should be soaked in water prior to mortaring. They said absolutely not! I have heard so many people say they soak the bricks but is this really the correct method? I have been going somewhere down the middle...I keep a spray bottle on hand and lightly mist the brick surfaces that will be getting mortared. The bricks seem to set quickly so I have to hurry to get them properly aligned.

Will mortar stick to a brick that has a thin coat of mortar on it? My soldiers have a 20 degree angle cut on them and when I mortared them together I left a very thin coat of mortar on the 20 degre face. Now I'm concerned the second course will not adhere properly to this...

~Bob

[Les]

Re: Mortar not sticking

If the mortar has a good bond - absolutly. BTW, I never soaked any of my bricks either and have had zero problems.

Les...

[dmun]

Re: Mortar not sticking

Firebricks are pretty porous: if they are bone dry, they will suck the water out of the mortar, and endanger the bond: mortars need to keep wet to set properly.

My experience with heat stop leads me to believe it will stick to anything. I don't think an existing layer of mortar will be a problem at all.

[diy]

Re: Mortar not sticking

For application with Fire bricks you must use proper refractory cement. For outdoor application Heatproof Screed is the correct material to use.

[enasfournos]

Re: Mortar not sticking

Hello.....
Have the same problem using fire clay,does any one know the correct ratio to mix cement and fire clay?
Have mixed 1:1 no luck, can't get it to stick to fire bricks,also tryed 2:1 no luck.if anyone knows the receipe please reply.
Thanks
gd

[FIREANDFLAMES]

Re: Mortar not sticking

When i build my oven i had a bucket of water and soaked the bricks for mabye 5 min. And a year later no cracks or nothin!

[jmhepworth]

Re: Mortar not sticking

I'm by no means a brick mason, but this is my experience. The mortar needs to be the consistency of peanut butter. If it's too wet, the bricks slide all over. If it's too dry, it doesn't adhere well. The Heatstop manufacturer made three recommendations to me. (1) Make sure the bricks are wet. I soak them and have had good success. If the brick is dry it sucks the moisture out of the mortar, as David pointed out. (2) Mix only what you can use in a few minutes. You cannot reconstitute refractory mortar like regular mortar by adding water to it. When it begins to set, it's not any good anymore. (3) mix with cold water. Warm water apparently starts the chemical reaction too quickly.

I make sure I press the brick into place so that mortar oozes out. For goo measure, I tap (sometimes it takes more of a smack than a tap) the brick with the butt of my trowel to set it into the mortar. I have no idea if that helps, but it seems to get the brick to stay in place a bit better.

I have 8 courses in plus the soldier course and have not had to use any support. Heatstop is very sticky.

Joe

[ThisOldGarageNJ]

Re: Mortar not sticking

I called the manufacturer of Heatstop 50, which is what I am using for my oven. I asked them if the firebricks should be soaked in water prior to mortaring. They said absolutely not!

The Heatstop manufacturer made three recommendations to me. (1) Make sure the bricks are wet. I soak them and have had good success. If the brick is dry it sucks the moisture out of the mortar, as David pointed out

I'm a little conused here, Or is the Heat Stop company a little conused ?

Any Comments

[pizza_bob]

Re: Mortar not sticking

Ugh!
I spoke to the manufacturer last week and they said the bricks should not be soaked. I'm just as confused too now!
I find it difficult to believe that there is not a professional mason on this site that knows how to use Heatstop 50 the correct way. It seems like it would be a balancing act of sorts...If you soak the brick then you can go with a slightly less water-downed Heatstop 50 mix. But a less water-downed mix then would suck moisture from the soaked brick and then have too much water in the joint. If you don't soak the brick then the water will go from mortar mix to the brick.

[ThisOldGarageNJ]

Re: Mortar not sticking

Hi Bob,
If this helps you at all, I briefly dipped my bricks in water before I laid them on heat stop that was mixed to a consistency of peanut butter. It has been three months now and i've have many fires and bakings and havent developed a single crack yet, And I have looked in the dome with a flashlight ater the oven has cooled down.

I just find it kinda strange that heat stop is giving out different information, Does anyone have a bag they can read and tell us if it says anything on the bag ?
Mark

[pizza_bob]

Re: Mortar not sticking

Hi Bob,
If this helps you at all, I briefly dipped my bricks in water before I laid them on heat stop that was mixed to a consistency of peanut butter. It has been three months now and i've have many fires and bakings and havent developed a single crack yet, And I have looked in the dome with a flashlight ater the oven has cooled down.

I just find it kinda strange that heat stop is giving out different information, Does anyone have a bag they can read and tell us if it says anything on the bag ?
Mark

Mark,
Yes that is reassuring to hear you have no cracks!
I went to the manufacturer's website and found the follwoing information and attached PDF. No mention of soaking bricks though...

Heat Stop - High Temperature Resistent Refractory Mortar