Summerhouse knot marks

[Jojoj123]

We have had a new summerhouse put up about 2/3 weeks ago. It was treated x2 with preservative and then x2 coats of cuprinol by the business we used. It looked fine when it arrived but is now covered with sap looking knot marks on all sides

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Is this something that was done incorrectly or is it just one of those things?

 

[JohnD]

sap will come out when the sun first gets on it and it gets hot.

When painting, you can use knotting, or aluminium primer, to seal it it.

I don't know a treatment with water-based stains.

I think I'd leave it till the end of the summer, then, using a heat gun, you can scrape it off and the remaining sap will bubble out. When cold, it hardens like varnish and you can scrape or sand it off. Then dab on some more of the treatment. You new paint will not quite match until it fades.

I use a dark brown shed and fence stain so it does not look as prominent as yours.

 

[Mr Chibs]

You can get clear and brown knotting solution, as I found when the second can is dark brown

 

[Jojoj123]

Can I just sand it down, put knotting solution over and repaint?

Sorry to hear about the brown

 

[JohnD]

it may still be soft, so try a scraper (and heat gun if you have one) first.

I rather think it will continue coming out during the summer.

If your "paint" is water based, I don't know if it will stick.

 

[Mr Chibs]

Can’t speak for exterior paint, but I’ve used it on all interior woodwork, and water based paints are good on top of the knotting solution.

Never heard of the heat gun technique, why not just try in an inconspicuous area sanding back, dab on the knotting (could use a cotton bud) then paint once dry.

 

[opps]

As above, waterbased paints should be fine over knotting solution. That said, if the knots are very resinous, you often need to drill and pull them out and fill with two pack or epoxy resin. John's heat gun method may work by making the resin so thin that drips out.

Knotting solution is not designed to actually hold back the sap. (eg the knot to the right hand side of the window).

 

[JohnD]

The heat gun makes it bubble out. So melted, and expanded, and pushed out by air or steam. Scrape it off to prevent it being reabsorbed as it cools.

I don't think I was told this, but noticed it when stripping old gloss paint. Might even have been in the days of blowlamps.