Filling/repainting basics for a much-slammed front door

[TryingHard24]

I'm a bit new to DIY exterior painting, so I'd appreciate some advice.

I'm repainting a timber exterior door and frame.
1) The door gets slammed a lot, so I want a filler/paint system that will withstand the vibrations as much as possible.
2) I say 'exterior', but it is under an open awning roof, so doesn't get much/any actual rain on it

I have limited time, so I'd like to save effort as much as possible on scraping the old paint off.

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so far:

I've had to take the _joints_ (e.g. between door panels) back to bare wood, due to the cracking of the paint and filler.

The _plain faces_ are old gloss on an acrylic primer. The primer is sound and I'd like to avoid removing it, if possible. I've had to chip off _some_ areas of the gloss topcoat as it was very cracked (20% of the total area). The rest of it is less cracked and could probably survive with just keying and repainting.

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So my questions are:

-For those areas where I stripped it back to bare wood:
1) With what do I fill the gaps between wood panels?
Woodfiller? Caulk? Woodfiller THEN Caulk on top? (The gaps are typically 2mm wide and 5mm deep). (I'm thinking that a layer of caulk would help absorb the vibrations from door-slamming).
2a) Do I prime the bare wood before filling it? Before I apply caulk?
2b) Generally, what is the correct order for applying Primer-Filler-Caulk-Undercoat.
3) I have a tin of water-based exterior primer-undercoat. Is that OK or do I need an acrylic undercoat?
4) Is standard oil-based gloss topcoat ok?
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For those areas where I have chipped-off the gloss topcoap and exposed the old acrylic primer :
5) Do I need to key/scratch the old primer before applying (water based) undercoat to it ?
6) what KIND of filler do I need to bring the thickness up to meet the areas where I kept the existing gloss (0.7mm)?

I imagine that the textbook answer is 'take everything back to bare wood', but would like to avoid doing that if possible

tia

 

[sparkwright]

-For those areas where I stripped it back to bare wood:
1) With what do I fill the gaps between wood panels?
Woodfiller? Caulk? Woodfiller THEN Caulk on top? (The gaps are typically 2mm wide and 5mm deep). (I'm thinking that a layer of caulk would help absorb the vibrations from door-slamming).
2a) Do I prime the bare wood before filling it? Before I apply caulk?
2b) Generally, what is the correct order for applying Primer-Filler-Caulk-Undercoat.
3) I have a tin of water-based exterior primer-undercoat. Is that OK or do I need an acrylic undercoat?
4) Is standard oil-based gloss topcoat ok?
---

For those areas where I have chipped-off the gloss topcoap and exposed the old acrylic primer :
5) Do I need to key/scratch the old primer before applying (water based) undercoat to it ?
6) what KIND of filler do I need to bring the thickness up to meet the areas where I kept the existing gloss (0.7mm)?

1) Exterior caulk or Decorators Mate for the gaps, as you say it is flexible for door slamming.

2) Prime bare wood first, then filler, then primer where you have sanded filler and scratched the wood, then caulk, then undercoat - generally speaking.

3) If you want oil-based gloss as a finish, oil-based undercoat is best IMO.

4) Standard oil-based gloss topcoat should be fine, though exterior gloss will always be recommended.

5) Always key or sand all old paintwork when painting wood to ensure good adhesion and long life.

6) A two part wood filler is always best for wood, it dries quickly, and sands well without crumbling too much. Again, old paintwork should be sanded before applying filler, otherwise it may not adhere well.

 

[opps]

Epoxy resin filler is more flexible than 2 pack but it much more expensive and harder to sand. d

Most epoxy fillers need very thorough mixing and most need a special caulking gun (approx £30+). This filler however can be dispensed with a standard caulking gun.

With regards to the cracks where the panels meet the rails and styles, standard caulk might work but if the panels are prone to expanding/contracting, you may find that regular caulk will crack. If that is the case then use a MS polymer, eg Sikaflex, CT1 or Puraflex 40. They are as flexible as silicone sealant and have the added benefit of being paintable (nb. you will need to coat them with waterbased primer first- oil based paints will not dry if you don't use the WB paint first).

Apropos the rest of the process, follow Sparkwrights sound advice.