Wood filler recommendation for exterior use

[Doug]

Need to fill a split in an exterior board - what brand(s) of wood filler perform well in this application after priming and painting?

Thanks.

Doug

[whit3rd]

If it's under zero stress, maybe you can get away with putty (I like Dap glazing compound). Better, though, to replace the board. You don't have any control of the interior moisture, it's gonna move after you apply any patch.

[krw]

I've used a variety of stuff from rotdoctor.com, with good results.

[DerbyDad03]

DuraGlas

Typically available anywhere Bondo is sold.

I used it to repair a rotted window sill. It's going on ten years which includes 10 rust belt winters. Still holding strong.

[Doug]

Thank you for the DuraGlas recommendation. Did you use Fiberglass backing when repairing the window sill? Was there any shrinkage / reduction in volume after the material was fully cured? What did you topcoat with - primer and paint or the materials recommended in the data sheet?

Thanks again!

DerbyDad03 wrote:

[Doug]

Thanks to all for the recommendations. Replacing the board is certainly the best long term solution. The condition is the result of a defective board being installed by some less than competant remodelers and not being identified by myself before it was painted.

Doug

Doug wrote:

[DerbyDad03]

I did not use fiberglass. I slightly overfilled the voids with the DuraGlas, just like you would with Bondo or dry wall mud and then sanded it smooth. Primed with exterior primer, painted with exterior paint.

Because of the fiberglass in the product it's a lot harder to sand than wood, Bondo, drywall mud, etc.

You also might want to gouge the split or undercut it to give the DuraGlas something to hold onto. Give it some "teeth" to lock it in.

[dadiOH]

Splits can be iffy. I wouldn't use any rigid filler, I'd use a caulk, then prime and paint.

[hubops]

Caulking - that was my first thought also... but don't know the size of the crack. Normal caulk will only work up-to a certain size opening. Perhaps a specialty caulking ? John T.

[dpb]

On 02/14/2017 6:04 AM, DerbyDad03 wrote: ...

What was the form of the voids? I used both Bondo and a fiberglass-enhanced version to repair areas on the barn siding when did the refurb on it. Most did _NOT_ hold up to the temperature cycling and wind-induced movement of the wood substrate more than 5 yr or so(*). I can imagine if were larger, deeper voids it _might_ be more successful, but for surface damage I can't recommend bondo as being very permanent based on the results I've had...not sure _any_ inflexible material will stand up.

(*) Noticed the other day, ring-shank siding nails driven into 100-yo first cut SYP wall studs have worked out where heads may be as much as

1/8" or more proud of surface. The buffeting of KS wind just causes so much movement even they don't hold permanently...

[Markem]

Durham's Rock Hard Water Putty

[woodchucker]

Use dap exterior grade caulk

[DerbyDad03]

I'll wager that barn siding subjected to KS winds moves a lot more than a first floor window sill on a 2 story colonial in the rust belt.

If my window sill moved enough to dislodge DuraGlas I'd move too. ;-)

[Doug]

Thanks again to all for the benefit of their experience.

Max. width of the void is ~1/4 - 3/8 in., and perhaps 10-12 in. OAL, tapering at each end.

Use of filler will be temporary until this board and others are replaced.

Doug

[e-mail] wrote:

[Doug]

dadiOH,

Thank you for the reply. I want to take the opportunioty to Thank You agian for the recommendations, guidance, and confidence you provided regarding refinishing my mahagony front door with Z Spar Flagship varnish. That was the best, most valuable input I have ever recevied for a home improvement project. The door still looks great almost 4 years later although a touch here and there may be beneficial.

Doug

"dadiOH" wrote:

[nailshooter41]

ing my mahagony

e input I have

almost 4 years

Doug -

You will rarely, if ever, see dadiOH give bad advice. I do all manner of re pair and finishing for a living and have to say his advice is usually spot on.

As was his thoughts on splits; wood moves on its own based on temps. Hard fillers aren't the ticket as they have no elasticity, and if the wood moves the patch material separates from the perimeter of the patch from repeated movement.

Epoxies, resins and their cousins are fine for interior use as you are usua lly repairing a piece that is acclimated to inside humidity from AC/furnace controls, so humidity doesn't fluctuate wildly. Nor do the temps. Most o f the time they aren't your optimal choice for exterior use.

Again, as he said, your best bet for splits, cracks wind shake, is a good c aulk. To do all my repair sealing, I use the ALEX 40 year with silicone tha t is available at the home stores. It hold paint very well, has great adhe sion, shrinks only a tiny bit, tools well and has something like 10% elasti city when cured.

Robert

[Leon]

Coming in late here but Butyl, printable, caulk remains very flexible for years on end and fills gaps pretty nicely. It is kinda messy though.

[bnwelch]

I have also found that polyurethane caulks have a tenacious grip, and hold paint well...

[Electric Comet]

wonder why it split

how big a split is it

[Bill]

After reading the rest of the thread, you're "coming to the party" now? Doug already answered this question (at least he gave dimensions).