# Board Cracking in House with an Outside Wood Heat Box



## mds120 (Nov 22, 2009)

Wall cracking in home with external wood heat.



We completed a home a little over a year ago. Fourteen months later we fixed 12 wall cracks. Mostly header cracks. Most taking off at an angle similar to what you might find with settling. All were cracked through the drywall, not just the mud. 



We used mesh tape and quick set. Two months later the cracks came back. Right after the heating system was turned on.

I’ve worked for the builder for a long time and he knows his stuff. *This house is unique in that it is heated from a wood burning fire box that sits outside the home. The wood heats liquid that is routed over the furnace. The fan from the furnace circulates the heat throughout the house*.

The builder is convinced an unbalanced heating system is causing drastic humidity and heat differences between rooms. He took readings and found the heat to vary as much as 27 degrees between rooms. The humidity differences vary about 20%. At one point he took heat readings at the vent in the basement which was 121 degrees while the reading upstairs was 112 degrees at the vent. 



We picture cut drywall around doors to avoid header cracks so I was amazed there was a problem. 

Both incidents of cracking occurred, according to the builder, after the heating system was started for the season. There are no other signs that might lead one to think there is settling other than the builder said all the doors in the home required adjusting which he did not do right away. He came back a few months later and all the doors had corrected themselves.

I know I can go along with the builder and agree it is the heating system. However, I am not one to leave a home owner hanging. I know I would not like to be left with permanent cracks in my new home. 

The heating contractor, as you can imagine, is not cooperative. The homeowner hired the contractor and the outside system was installed after the builder finished the home.


Should I fix the cracks again, this time cutting back into the cracks a little? If the actual rock is cracking, I'm not sure that the repaired joints would hold any better if the root cause of the problem is not addressed. 


Does anyone have experience with this type of heating system and if so, did you have issues with cracking. 
Thanks,


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## [email protected] (Dec 23, 2008)

It is less the heating system itself than the lack of a whole house humidifier (mounts directly to the plenum). Has nothing to do with type of fuel, except that direct wood heat would dry out the interior worse than gas or electric. Being a heat exchange system, it would be no worse than a standard furnace. The inside humidity in the winter should be set at 25-28%. I turn mine to 30%, wait for my patio door to frost up, then back it off to 27%. The humidifier should cost about $450 installed by the hvac guy.

I'd fix the cracks, vee groove, mesh tape, etc. And advise the ho that unless hevgets the humidifier, he'll continue to have problems.

But if you have cracks that break rock diagonally, I'd be suspect of the house moving as well. When I see that kind of crack over one header, I look around for a corresponding crack, on an adjoining wall. If the DR window cracked, and the kitchen window around the corner did too, would indicate that corner of the house dropped. The header lumber was also way green, but should have done most of it's shrinking in a full year of hot/cold cycles.


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## rebel20 (Jun 4, 2009)

Here is where you shoud understand whats happening. Basically darren sums it up.
http://www.sbcindustry.com/images/technotes/T-GypsumInstallation09.pdf


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## Custom Drywall Svc. (Oct 31, 2008)

mds120 said:


> Wall cracking in home with external wood heat.
> 
> 
> 
> ...



I was just about to ask if you 'pictured framed' or picture cut the doors / windows until i read you did that as well. With the non-straight, not horizontal / vertical cracking -- its definitely a settling or movement issue.

Yes, you should go back to fix it at least one more time, and like Darren says v-groove it out....however, i would apply Weldcrete deep inside the cracks with a small brush before applying any tape, drywall mud / quickset. It may sound unconventional and a bit odd, but I addressed the use of this product in a thread somewhere in the archives. If you don't know what Weldcrete is, go head and Google it. Its pretty cheap, and for us, has worked.

Let's just say, if the way you would normally repair the settling crack gave you 80% assurance that it might not come back....Weldcrete would simply bump that to a 90%.

...not saying its 100% (because it hasn't been officially tested by the drywall industry specifically for this use), but it surely doesn't hurt.

when you apply the weldcrete however, just make sure you let it sit for at least an hour inside the cracks to dry, allowing it to BOND.

...then do the normal repairs....mesh tape, mud, etc.


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## mds120 (Nov 22, 2009)

Is the Weldcrete the same as plaster-weld? I assume not or the same company would not sell two products.


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## [email protected] (Dec 23, 2008)

What does mds stand for?


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## mds120 (Nov 22, 2009)

Darren - I assume you are Lee's son?


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## [email protected] (Dec 23, 2008)

Nope, Bill's.


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## Custom Drywall Svc. (Oct 31, 2008)

mds120 said:


> Is the Weldcrete the same as plaster-weld? I assume not or the same company would not sell two products.



http://www.larsenproducts.com/weldcrete.htm

http://www.larsenproducts.com/faq.htm


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## Whitey97 (Jan 27, 2009)

Darren, between you and Silver. The three of us could take on any drywall related question there is. I feel so lucky to not be surrounded by idiots all the time!


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