Painting exterior tongue and groove - stringy paint problem

[Mike in Kettering]

Hi,

I make garden furniture and a few months back I painted some exterior tongue and groove boards using Cuprinol paint. As the timber has contracted over the summer and the boards have moved apart, in places there are thin strands of paint straddling every pair of boards which isn't particularly sightly.

I am wondering whether this is because the paint is too thick and I should dilute it before spraying it on, three thin coats rather than two thick coats. Would like to know what you guys think.

Regards,

Mike

 

[KenGMac]

Mike in Kettering, good evening.

I see this is your first post on the board, if no one else does Welcome to the board.

When you painted the T&G, had you fabricated the item?

If so, given the present unusual weather conditions, prolonged very warm, dry Etc. will cause the timber, if not kiln dried at the time of fabrication to shrink.

I assume that you can now see areas of "Bare Wood" where the tongues have shrunk back.

I do not think the paint was too thick, the paint is probably performing as intended, that being it is trying very hard to adhere to itself, but cannot bridge the gap occasioned by the shrinking timber, the paint film is not capable of bridging such large gaps so the paint splits and thin strips of paint occur.

One way around the problem is to paint all the individual timbers prior assembly of the piece, meaning paint all surfaces prior to assembly, but after fabrication of the piece, tends to be messy, painting all 4 surfaces of the components, but advantages are that even if water gets in to untreated areas rot will be delayed, and if shrinkage occurs in the substrate timber, the visual effect of untreated timber is reduced.

one last point, allow the paint to dry completely prior to assembling the various components of the piece.

Ken

 

[Mike in Kettering]

Hi Ken,

Thank you for your reply. Your solution does make sense, painting prior to assembly would be a solution but it would take up more space and be much more time consuming. However it seems that to get the best finish I don't have much choice.

Mike

 

[opps]

I concur with KenGmac's assessment of "failure" being the result of expansion.

Although time consuming, you could start by running a thin bead of an MS polymer "caulk" to provide an expansion bridge. They have the flexibility of silicone and the advantage of being paintable.

They are however more expensive than silicone or caulk.

Examples include CT1 and Sikaflex. There are loads of other brands.

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