# caulk for Hardy siding



## painterdude

just looked at an ext. job with Hardy Plank siding. After 6 years some of the butt joints that were caulked are cracking, probably just as a result of sun etc. Is there any specific type of caulking that would help in this situation, or just the typical silicon acrylic SW type? thanks for any suggestions. Pd


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## Paintuh4Life

I use DAP Sidewinder. You'll need to use a rag dipped in paint thinner to smooth it, but it's high performance. :thumbsup:


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## ewingpainting.net

Check this thread
www.painttalk.com/f6/butt-joints-sideing-14462/


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## WisePainter

duo-sil, used it in fla. on hardie board.

i made a thread way back about it, search it, worth it.


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## NACE

Hardi has an expansion rate of 1/8" per 18' I think. So any elastomeric sealent with 99% memory and at least 60+% elongation should suffice. Am I wrong on this? Caulk is flexible but does not have elongation and memory, sealant has the properties that are required for disimilar surfaces and joints that move in most surface types.


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## ewingpainting.net

I think there are plenty of caulks that can handle the elongation, the problem is finding a coating that can handle it.


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## Builtmany

OSI Quad because it's available in the exact Hardi Colors.


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## StripandCaulk

if the hardie siding was installed properly you should not have any caulk in your buttjoints at all. there should be flashing installed behind the joints, and that is on top of your tyvek/ house wrap backing. i would gut the caulk out and not recaulk with anything. this might help you out though

http://www.jameshardie.com/pdf/install/hardieplank-hz5.pdf


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## Builtmany

StripandCaulk said:


> if the hardie siding was installed properly you should not have any caulk in your buttjoints at all.
> 
> http://www.jameshardie.com/pdf/install/hardieplank-hz5.pdf


That is correct but it sounded like someone already did the job wrong. I have seen many Hadri jobs installed improperly. Butt joints should be 2 factory painted ends together, no cuts and no caulk.


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## StripandCaulk

Builtmany said:


> That is correct but it sounded like someone already did the job wrong. I have seen many Hadri jobs installed improperly. Butt joints should be 2 factory painted ends together, no cuts and no caulk.


not surprised, everyone thinks they can be a contractor. i dont know how big the gap is, but hardie expands and contracts less than wood. I would use something like GE Groove, its has more silicone than any SW caulk ive ever tried. hopefully they at least sized the boards right. key is to get rid of the caulk thats already on there, its probably crap if its done after 6 years.


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## danpaints

check out "big stretch"


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## finishesbykevyn

danpaints said:


> check out "big stretch"


 I'm gonna have to agree with the no caulking thing. The joins should be strategically placed over the flat section of the next board under it. There is house wrap, and flashing designed for any water that does get trapped. Any caulking you put on there will eventually split or crack and look plain ugly. Mind you, every situation is different...:thumbup: And whatever you do, don't caulk around the flashing and drip edges, they were designed for a reason..


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## Builtmany

Certain Teed makes the same type of siding as Hardi they just call it fiber cement. They sell the caulk to go with it and it happens to be OSI Quad asj the place that sells the siding. The only other alternative would be Dap Sidewinder as its based on the same properties, a mineral spirits base (does not clean with water). Now, why not use the OSI in the exact color that matches? Much better IMO Anyone that has used OSI Ouad knows just how durable it can be in extreme weather outdoors. The only drawback is cleanup and tooling it with paint thinner vs. water.


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## Dschadt

Stripandcaulk seems to be right on. Wish it had been done right the 1st time. Ive seen many people use the colored hardy caulk on prefinish.


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