Gap Filling - Do's and Dont's?

From prep to final coat. Discuss it here

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PDT Armour Coatings
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Joined: Sat Nov 23, 2013 8:13 pm

Gap Filling - Do's and Dont's?

Post by PDT Armour Coatings » Fri Dec 13, 2013 8:23 pm

Hi, Just a question to see what other people on here think about the role of gapfilling on exterior repaints?

I recently had an external repaint on a chamfer board house, on one of the final days, I had another tradesman there helping me do touch ups around the house and he asked me about my no gapping.

I said that as a general rule, I don't gap fill the chamfer or weatherboard overlaps. He asked why and said that where he usually works, they gap everything before they start with S20 and leave it for at least 24 hours before over-painting. I said that I don't gap the overlaps because that is just what I was taught, I then said that I was told that it is to do with moisture, breathing, and cracking of the gaps at a later stage.
The amount of water that gets into wall cavities is amazing, just look at a weep hole that a renderer has not cut out, and the amount of efflorescence that comes from it and bubbles away your paint. To protect the timer as much as possible, and allow it to not rot, we don't do overlaps.

However, I do see the other side of the coin, and am not sure which is the best way of doing things. Obviously, if you had a decent chippy, then it is not so much of an issue, however I have seen 1/4" gaps between the lengths of new cladding that the chippys have just simply not butted up correctly.

What is the thoughts and opinions of this of people on this forum

P.S. /i have noticed on the tubes of S20 and Original that it states quite clearly on the tube to not gap fill under weather and chamfer boards on the overlaps.

James Thompson
PDT Armour Coatings

tassie painter
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Re: Gap Filling - Do's and Dont's?

Post by tassie painter » Tue Jan 28, 2014 8:56 am


the way i was taught was not to gap under weatherboards because it eventually cracks out from movement in the boards, you have to allow the boards to breath. alot of the gaps i see are way to big for no more gaps anyway you really need something way more flexible if you decide to do it. i gap everywhere else except underneath the boards.

the amount of times i have had to scrape out gaps that have cracked out everywhere on repaints is ridiculous.
but i do know some tradesman that do gap underneath weatherboards it looks good but not for long.

i also have seen alot of messy jobs where so called tradesman gap under the boards and leave a fat edge with the gaps on the face of the board and then paint over it instead of feathering it out with a damp brush, looks so bad especially if you are using gloss.

if i were you i would stick to what you were taught because its the right method.

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Re: Gap Filling - Do's and Dont's?

Post by Pacificpainters » Wed Feb 26, 2014 10:27 am

I always believed that I should caulk, but I really got attacked on another forum because they said I was totally wrong.

In the states they sell wedges to maintain a crack in between the boards. I will try and find the site that advertises these wedges and post it.

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