# To caulk or not to caulk, that is the question.



## Brian C (Oct 8, 2011)

Hi gang, 

in Australia we refer to exterior timber siding on a house as weatherboards. I was wondering if you caulk the bottom edge of the boards ?

Some homeowners are quite adamant for all gaps to be caulked. I must agree that a nice slick looking job with no gaps in the boards looks professional, but what about the long term durability of the caulk ?

The extremes in temperate causes expansion and compression of the timber and the caulk could fail in some instances. I find that old timber homes seem to have acclimatised over the years and tend to be more stable than new timber clad houses. I haven't had any issues with caulking the underneath edge of timber siding on old homes. 

What ya think ? Appreciate you chiming in.


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## Delta Painting (Apr 27, 2010)

Where the siding meets the trim yes the bottom of the weatherboards I would not caulk.


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## DeanV (Apr 18, 2007)

Caulking the bottom of horizontal siding is never recommended. That joint is supposed to stay open.


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## stelzerpaintinginc. (May 9, 2012)

The underneath side should never be caulked. Even accumulated paint on the underneath edge should be scored to insure those weatherboards can vent heat & moisture. 

Stuff like this comes up all the time, especially on older homes...people choosing form over function, then the next owner and next painter pay the price. 


Stelzer Painting Inc.


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## CApainter (Jun 29, 2007)

Look at the siding as gills on a shark.


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## Krittterkare (Jul 12, 2013)

Never!


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## mudbone (Dec 26, 2011)

Needs to breathe!


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## Rbriggs82 (Jul 9, 2012)

Don't do it!!!! I agree it looks nicer but you're asking for trouble down the road.


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## Red dog (Jul 20, 2014)

I never caulk underneath lap siding of any kind.It needs to breath.


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## epretot (Dec 17, 2011)

I have to go with the others.

In fact, I will probably be opening the gap on my current project because the paint has filled in the gap.


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## Brian C (Oct 8, 2011)

I agree with all the comments above, but I have had a few requests from ignorant builders to caulk everything.


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## Damon T (Nov 22, 2008)

Even if a builder or ho asked me to caulk the bottom I would refuse. 


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## Delta Painting (Apr 27, 2010)

Brian C said:


> I agree with all the comments above, but I have had a few requests from ignorant builders to caulk everything.



ignorant builders...:thumbsup:


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## capn26 (Aug 17, 2014)

Okay, I agree with never caulking wood siding. The wood itself needs to breathe. But if it's a cement based siding with a vapor barrier behind it, what is there to breath? I know that products like tyvek and typar are supposed to breath but with it flat against the plywood and the siding tight on the other side that's a joke. Guys around here have chalked the bottom of hardy board for years. I've removed it up to ten years later and seen no adverse affects.


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## journeymanPainter (Feb 26, 2014)

capn26 said:


> Okay, I agree with never caulking wood siding. The wood itself needs to breathe. But if it's a cement based siding with a vapor barrier behind it, what is there to breath? I know that products like tyvek and typar are supposed to breath but with it flat against the plywood and the siding tight on the other side that's a joke. Guys around here have chalked the bottom of hardy board for years. I've removed it up to ten years later and seen no adverse affects.


There should be a rain screen between the tyvex, and the siding, that allows air flow, and expansion/retraction. There should be a little bit of play in the siding for all of that

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## capn26 (Aug 17, 2014)

True. That's exactly how it should be done. However it's not actually required by code in north carolina. We actually have a contractor in town that is enormous who puts vinyl directly on plywood. They are mega rich, control the land, so they keep building away. And they have created a whole market for fixing their homes behind them.


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## Hissing Cobra (Feb 24, 2014)

I never caulk the bottom of the clapboards. It'll only cause problems further on down the road. I do caulk the sides where they butt up against the corner boards.


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## mudbone (Dec 26, 2011)

Damon T said:


> Even if a builder or ho asked me to caulk the bottom I would refuse.
> 
> 
> Sent from my iPad using PaintTalk.com


Yes that would be the" bottom" line for me as well!:whistling2:


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## Roamer (Jul 5, 2010)

stelzerpaintinginc. said:


> Stuff like this comes up all the time, especially on older homes...people choosing form over function, then the next owner and next painter pay the price.
> 
> 
> Stelzer Painting Inc.


This is what we encounter in many instances. Weathered siding that has been painted repeatedly and the lines between boards are sometimes filled and other times not. Not very aesthetic if you choose function over form.

You could try the Wedge Vent. 
http://www.wedgevent.com/index.htm


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## ridesarize (Jun 19, 2012)

I agree with everyone, no caulking on bottom, and home needs to allow breathing, venting of siding system. Even tyvek systems and liquid applied moisture barrier systems benefit from it.


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## epretot (Dec 17, 2011)

Do you guys see any pitfalls to caulking all of these joints?

I ask because I painted two pergolas similar to this one with rot problems last season.
The problem areas were where the 2x4 meets the 2x6.


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## stelzerpaintinginc. (May 9, 2012)

epretot said:


> Do you guys see any pitfalls to caulking all of these joints?
> 
> 
> 
> ...



I don't think caulking will hold up for long if you do. Those boards will expand & contract at different rates throughout the day, so I wouldn't advise caulking them. 

It's been my experience that many pergolas start rotting way too soon because of either poor construction or lack of protective coating on top & end grains. 


Stelzer Painting Inc.


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## epretot (Dec 17, 2011)

The carpenter pre-preimed the material with latex. I sanded and re-primed using a long oil. I'm concerned about tanin bleed from the areas under the 2x4's that don't have oil on them. I was thinking they might leach down. I don't suppose the caulk would help with that either.


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## Gough (Nov 24, 2010)

I just cringe when I see exterior projects like that. They're designed to trap water and start failing as soon as the first rain falls.


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## epretot (Dec 17, 2011)

Gough said:


> I just cringe when I see exterior projects like that. They're designed to trap water and start failing as soon as the first rain falls.


The 2x6's should have been flashed. They make a pre-bent piece for it. It might have added 2-4 hrs for the carpenter.

Over-caulking is my concern.


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## Gough (Nov 24, 2010)

epretot said:


> The 2x6's should have been flashed. They make a pre-bent piece for it. It might have added 2-4 hrs for the carpenter.
> 
> Over-caulking is my concern.


I think my main worry would be the caulking trapping water and accelerating the rot process.

You're right on that flashing would have been a better solution. Once again, it's the "leave it for to painter" game.


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## Zman828 (Mar 11, 2013)

I agree, no caulking on the bottom. I've met people who caulk everything and I have met some who caulk nothing...
_________________
Straight Edge Painting
painters in Jacksonville fl


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## PRC (Aug 28, 2014)

Don't caulk. I just finished a job where the previous painters had caulked all the bottoms of 170 yr. old clapboards. It caused massive failure on most of the building because it couldn't breathe. This siding was on studs with no vapor barrier, but even new work shouldn't be sealed up that tight.


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## PRC (Aug 28, 2014)

Here's some of what we ran into.


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## PRC (Aug 28, 2014)

Forgot to turn the pic.


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## Repaintpro (Oct 2, 2012)

epretot said:


> Do you guys see any pitfalls to caulking all of these joints?
> 
> I ask because I painted two pergolas similar to this one with rot problems last season.
> The problem areas were where the 2x4 meets the 2x6.



Like all of you here we have done heaps of these where the builder requires it to be gapped. The builder wants it looking nice for the customer, so how about getting the carpenter who normally has the attitude of "oh the painter will fix it" to make his cuts very neat and tight! 

BTW the ones in your pic looked pretty good for a pergola!


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