Hi all

Got plenty of caulking and filling coming up... I'd not heard of backer rod until recently, and having read up a bit on it it seems there's many others who are unaware of it. The big name stores don't seem to sell it either, which made me wonder how commonly it's used...

So, any fans of backer rod here for use in channels, chases, etc prior to caulking?

On a more technical note, there's a fair bit of online chat RE open vs closed cell. Apparently, open cell is more pliable/flexible and better for squeezing into gaps but not good if it gets wet. Also, they say closed sell off gases when cut or torn which can cause problems and even cause the caulk to bubble. But that's mainly from US sites/forums. Here in the UK, there's not much talk of it and the shops that do sell it seem to just sell "standard" stuff (which is closed cell). Does anyone know anything about this open/closed cell business?

Cheers

I've never heard of "backer rod" until I read your post. Looks useful stuff and when I think back it would have been very useful for some jobs!

Sorry therefore that I cannot shed any light on the different performances of open vs closed cell. However I would be surprised if the amount of released gas from closed cell would cause caulking to bubble, especially silicone, as this is very tough stuff when cured (which happens pretty rapidly).

I have used it but don't recall what type it was. Ended up with a load of different sizes worked really well to ensure I had a good seal and meant that the caulk had something to support it. It is quite cheap to buy.

Many thanks for all the replies. Much appreciated.

Funnily enough, I have found bits of newspaper as described from old repairs by previous occupants and wondered what that was all about! I thought it was the sign of some short-cutting bodges, but perhaps it was a more common technique than I gave it credit for!

FYI, having spoken to the manufacturer he says to allow time for it to off gas if being cut or punctured before adding any sealant, but doesn't state why.

Very interesting that so many people have never heard of this stuff and yet for those that have they seem to think it quite indispensable. So much so that some of the suppliers only sell the smaller diameter stuff in reels over a kilometre long!!

You may find this article informative.

https://sealnoseal.org/PDF/BackerRod/TechRevBackRods.pdf

Thanks for the replies and also for the pdf link which was an interesting read :)