# Caulking exterior corner boards



## Damon T (Nov 22, 2008)

So we are on a project doing 20 bump-outs on townhomes. I've noticed that corner boards are rarely caulked, and it's true on these as well. Me inclination is to caulk them, but curious why they're rarely caulked (besides laziness, as all the other joints are typically caulked). Any thoughts? 



Sent from my iPad using PaintTalk.com


----------



## Brian C (Oct 8, 2011)

I always caulk any vertical join in the timber.


----------



## Jmayspaint (Mar 26, 2013)

I've noticed that too. Here in the mountains there are a lot of cedar sided homes. Some of them are caulked at the corner boards, and some aren't. I really don't think the primary reason is laziness or pour workmanship. Some of these houses are very nicely done. Back primed siding, good paint job, etc., but the corners will be left open.

I believe there is a school of thought that if the house is properly built, caulking the corner boards has little value as an insulator. Its similar to caulking butt joints, or even caulking the laps on the siding. If siding is designed not to be air tight anyway, and needs to move with seasonal temperature changes, then caulking the corner boards becomes a purely ascetic decision. 

The value of caulking places like where corners meet siding is debatable I'm sure, but some people and builders, think it serves little purpose on a well built house and just looks tacky.


----------



## Brian C (Oct 8, 2011)

I think that if the end grain of the boards are not primed before fixing to the house, then capillary action from moisture will rot the ends of the timber. Prime and caulk can alleviate this problem.


----------



## stelzerpaintinginc. (May 9, 2012)

Damon T said:


> So we are on a project doing 20 bump-outs on townhomes. I've noticed that corner boards are rarely caulked, and it's true on these as well. Me inclination is to caulk them, but curious why they're rarely caulked (besides laziness, as all the other joints are typically caulked). Any thoughts?
> 
> 
> 
> Sent from my iPad using PaintTalk.com



The funny thing is, if you ask 5 builders that question you'll get 5 different answers. Since many of the tasks of caulking are often relegated to the painter, (due to either an oversight or omission of the sider), it's sometimes hard to know what SHOULD be caulked. 

From my understanding, different siding/corner board variations call for different specs. Sooo, if you're really looking for an answer perhaps a pic might shed some clarity. 


Stelzer Painting Inc.


----------



## vermontpainter (Dec 24, 2007)

Shingle style or clap?


----------



## Epoxy Pro (Oct 7, 2012)

Shingle style no we don't caulk, claps yes. Like Jmays said every one will give a different answer and reason as to why or why not caulk.


----------



## Damon T (Nov 22, 2008)

This one has the vertical cedar 1x4's, next to some type of hardi panel. The panel is caulked to the corner boards, but none of the joint where the corner boards meet each other are caulked. And on lap siding houses I've seen the same thing. The siding is caulked to the corner, but the corners aren't caulked to themselves. That's on both hardi and cedar lap siding. 

Fwiw I typically end up caulked butt joints, even if they weren't caulked before. 




Sent from my iPad using PaintTalk.com


----------



## journeymanPainter (Feb 26, 2014)

I hate it when boards meet in corners, or on posts and they aren't caulked. What also drives me up the wall is when you have 2 our more facia boards, and noon of then are caulked

Sent from my SGH-T989D using PaintTalk.com mobile app


----------



## Hissing Cobra (Feb 24, 2014)

I caulk them on every job that I do and wipe excess off with a wet rag so it doesn't look like a sloppy mess (I like the keep the caulking in the cracks only and not on the face of the board). I then let the caulking dry for a few hours before applying the top coats of paint. They look awesome when I'm done but then I go back weeks later and find that both boards moved by expanding and contracting, forcing some of the caulk out of the opening.


----------



## mudbone (Dec 26, 2011)

Hissing Cobra said:


> I caulk them on every job that I do and wipe excess off with a wet rag so it doesn't look like a sloppy mess (I like the keep the caulking in the cracks only and not on the face of the board). I then let the caulking dry for a few hours before applying the top coats of paint. They look awesome when I'm done but then I go back weeks later and find that both boards moved by expanding and contracting, forcing some of the caulk out of the opening.


Type of caulk using?


----------



## Hissing Cobra (Feb 24, 2014)

Dap Alex Plus. It only seems to do that on corner boards and not on overhangs or rake boards.


----------



## DeanV (Apr 18, 2007)

Code here calls for windows to be caulked on top and sides only leaving bottom open to drain. We have had builders insist on caulking all sides, no sides, three sides, etc. We have had inspectors require the bottom edge and require caulked bottom edge to be cut out. We have had siding installers threaten to void the siding warranty if we caulked window trim to the window.

Interestingly, the PDCA p11-5 caulk requirements excludes caulking on exteriors as a painter's responsibility unless otherwise specified.


----------



## Gough (Nov 24, 2010)

DeanV said:


> Code here calls for windows to be caulked on top and sides only leaving bottom open to drain. We have had builders insist on caulking all sides, no sides, three sides, etc. We have had inspectors require the bottom edge and require caulked bottom edge to be cut out. We have had siding installers threaten to void the siding warranty if we caulked window trim to the window.
> 
> Interestingly, the PDCA p11-5 caulk requirements excludes caulking on exteriors as a painter's responsibility unless otherwise specified.


What's the builders' approach with HardiPlank with the mfg. specs calling for a 1/4" gap above window?

The biggest issue we see is builders using caulk to weatherproof at corners, windows , etc., instead of detailing the flashing and WRB properly. If that's done properly, the caulk is mainly aesthetic.


----------



## DeanV (Apr 18, 2007)

I think that is their view, the tape, flashing, etc weather proof it.

How about battens as well? I believe not caulking those voids warranty as well. It is rare we see battens caulked on new homes.

usually with hardie siding we have Miratec trim around windows with flashing on top.


----------



## Gough (Nov 24, 2010)

DeanV said:


> I think that is their view, the tape, flashing, etc weather proof it.
> 
> How about battens as well? I believe not caulking those voids warranty as well. It is rare we see battens caulked on new homes.
> 
> usually with hardie siding we have Miratec trim around windows with flashing on top.


Maybe in your neck of the woods the contractors do a better job with that detailing than the outfits around here, they'd be hard pressed to do a worse job. Windows, for example. After looking at installations for several decades, I finally saw some done correctly...last year. They generally all use housewrap and flashing, they just don't use them correctly.


----------



## DeanV (Apr 18, 2007)

I am probably not the best judge of if they have done it correctly. All I know for certain is that there is a lot ln siding the rests directly on top of flashing with no gap at all.


----------



## Gough (Nov 24, 2010)

DeanV said:


> I am probably not the best judge of if they have done it correctly. All I know for certain is that there is a lot ln siding the rests directly on top of flashing with no gap at all.


While the air gap as part of a "ventilated rain screen assembly" is probably the best, just making sure that liquid water will drain to the outside makes a big difference. We see flashing tape, drip edge, and housewrap installed in such a manner that it diverts water into the wall, rather than away.


----------



## ridesarize (Jun 19, 2012)

Gough said:


> While the air gap as part of a "ventilated rain screen assembly" is probably the best, just making sure that liquid water will drain to the outside makes a big difference. We see flashing tape, drip edge, and housewrap installed in such a manner that it diverts water into the wall, rather than away.


All exactly correct, we have one builder we with closely and analyze all flashing and gaps that need to be there above flashing, as well as back primed siding, primed cuts, rips. Flashing must divert moisture instead of it puddling.


----------



## finishesbykevyn (Apr 14, 2010)

Gough said:


> While the air gap as part of a "ventilated rain screen assembly" is probably the best, just making sure that liquid water will drain to the outside makes a big difference. We see flashing tape, drip edge, and housewrap installed in such a manner that it diverts water into the wall, rather than away.


Soooo true! I've fixed more rotten trim this summer because of improper flashing and gapping than you can shake a paint brush at! I'm mostly talking about people putting thier bottom trim directly onto the shingles with no gap for breathing. All the junk gets trapped inbetween the roof and trim and rots it out..
what's up with that?! Keeps me busy anyway and let's me work on my carpentry..


----------



## ridesarize (Jun 19, 2012)

So I was reading this thread last night not knowing it would help me troubleshoot wood deterioration (and hardiplank) today.

I told a h.o. yesterday water might be coming in from above corner boards but would be hard to track down. Gave the accurate conclusion today.

Awesomeness


----------



## Gough (Nov 24, 2010)

ridesarize said:


> So I was reading this thread last night not knowing it would help me troubleshoot wood deterioration (and hardiplank) today.
> 
> I told a h.o. yesterday water might be coming in from above corner boards but would be hard to track down. Gave the accurate conclusion today.
> 
> Awesomeness


Nice.... They obviously ignored Hardie's installation instructions.

Is that a wood batten on top of the horizontal trim in the first photo?

The metal window frame in the second photo is nicely detailed to catch the water. I guess it must not rain much where you are ( checks profile ). Oops.

How old is this house? Around here, we're seeing stuff like that in 10-15 year-old houses.


----------



## ridesarize (Jun 19, 2012)

Gough said:


> Nice.... They obviously ignored Hardie's installation instructions.
> 
> Is that a wood batten on top of the horizontal trim in the first photo?
> 
> ...


The first pic is a corner board about 5 feet above the second shot (vinyl window) . I don't believe the second one is done correctly either, it is all soft as well. The header trim in second pic is partially caulked, where there should be a 1/4" gap, and I think the cornerboard should run down and belly bands and header trim should butt up to it.
The corner trim just sucked up water from flashing area.
The previous owner had some areas replaced with horizontal trim butting to corner board, and they primed the new pieces but no paint. Which led to some corner trim dry rotting anyway.

This home is 12 years old approximately.. .


----------



## Gough (Nov 24, 2010)

ridesarize said:


> The first pic is a corner board about 5 feet above the second shot (vinyl window) . I don't believe the second one is done correctly either, it is all soft as well. The header trim in second pic is partially caulked, where there should be a 1/4" gap, and I think the cornerboard should run down and belly bands and header trim should butt up to it.
> The corner trim just sucked up water from flashing area.
> The previous owner had some areas replaced with horizontal trim butting to corner board, and they primed the new pieces but no paint. Which led to some corner trim dry rotting anyway.
> 
> This home is 12 years old approximately.. .


'Zactly.

The drainage gaps with Hardi seems to be one of the more overlooked details. Ignore it at your peril.

In the past few years, we've repaired several houses of that vintage. Average cost: ~$40K. That's a shock for clients living in what they think is a nearly new house. Guys were building McMansions who shouldn't have been building dog houses.


----------



## ridesarize (Jun 19, 2012)

I like that, mcmansions.


----------



## finishesbykevyn (Apr 14, 2010)

Dap caulking is garbage in my books hissing cobra. Ive been using the "Mono" brand for exterior. About twice as expensive but just soo nice. I also use it for my crown mouldings cause they always want to split on ya..Has anyone else used that? Thoughts?

Sent from my SGH-I747M using PaintTalk.com mobile app


----------

