Choosing the best filler for exterior wood takes a little bit of consideration. There are different types of filler for different types of repair, and dozens of brands available for each type of filler.
You’re asking the filler to do a lot too. It needs to withstand the expansion and contraction of the wood that occurs naturally with the weather. It also needs to withstand moisture and not deteriorate over time. Oh, and sometimes it needs to keep water out and prevent rot.
I’ve been a Decorator for over 20 years, and I spend most of my time during the warmer months working on exterior decorating projects. I thought I’d take a little bit of time to sit down and write a quick blog on the best filler for exterior wood.
I’ll start by listing the different types of filler available, then I’ll go into what I think is the best choice for each type of filler. Follow this advice and your repaired wood should look good and last.
Feel free to skip ahead if you already know which type of filler you need.
The Different Types of Filler for Exterior Wood
- Wood hardener – I know this isn’t really a filler, but it’s often used to treat rotted timber before applying filler.
- Water-based wood fillers – These usually come ready mixed, but you can buy powder versions. You might use them to fill pin holes or to blend into the original colour of the wood.
- 2-pack wood filler – This is most used by Decorators and is great for small to medium size repairs. You mix an activator with the filler to make it set.
- Epoxy wood filler – Genuinely the best filler for exterior wood when making a repair, but this option can be very expensive.
- Decorators caulk – Great for filling the joins and edges of exterior wood before painting.
- Glazing Sealant – Used to seal and hold panes of glass on timber windows.
The Best Wood Hardeners
When making a repair to rotted timber, you should start by removing as much rotted wood as you can. Then you might treat the remaining wood with hardener. This seals the wood, stops water from penetrating, and stops further rot. Also, as the name suggests, it hardens the wood, which gives you a good solid base on which to make your repair.
There are two different types of wood hardener; Epoxy wood hardener is heavy-duty, so you might use it for treating wood on big repairs before applying epoxy wood filler. You mix two components together which causes it to set.
And water-based wood hardener, which is easier to use, more environmentally friendly, and suitable for most situations.
Water-Based Wood Hardener
The water-based wood hardener I use is Toupret. It’s thin, so penetrates deep into the timber. It also sets reasonably quickly, so you can apply your chosen wood filler soon after.
You’ll find this product easy to use, dependable, and reasonably priced. Just get plenty on with a brush or roller, without allowing it to pool. I use Toupret Wood Hardener for most of my exterior repairs.
Epoxy Wood Hardener
If you are in any doubt, and you want something heavier duty, then go for Oxera Easy Mix Stabiliser. This sets so hard that if you leave your paintbrush in it afterwards, after it sets, you could use the bristles as a hammer!
Only mix what you need for the job in hand, otherwise it gets wasted. Oh, and wait a few hours from applying the stabiliser before applying your exterior wood filler.
Best Water-Based Filler for Exterior Wood
Using the wrong water-based filler for exterior wood can lead to problems. If the material contains too much water, then the wood around the hole can swell as it absorbs the moisture. Then you sand and paint, only for the wood to contract afterwards and break the seal of the paint. Your repair fails.
So, even if you don’t go for my recommendation, at least ensure the product you do choose is suitable for use on exterior wood.
Water-based wood filler is quick and easy to use. You might apply it to mitres and pin holes caused by nails in new wood.
It’s also good for timber that you are applying stain or varnish to. You can get water-based fillers in brown as well as white, and it also absorbs some of the stain or varnish and takes on its colour.
The most popular product for this type of filler is Toupret Wood Filler. I use a lot of this product, both inside and out. It’s easy to mix, easy to use, isn’t too expensive, and does the job brilliantly. I think it’s the most popular choice amongst Professional Decorators too (I always see it being talked about online). Toupret never lets you down.
The Best Two Pack Wood Fillers
There are loads of two-pack wood fillers on the market, and they all do a similar job to a point. Some sag when you’re applying them, so they’re harder to work will. Some contain a chemical called styrene, which smells lovely, but isn’t exactly healthy, so wear a mask when sanding.
My favourite is HB42 Ultimate Wood Filler: it doesn’t contain styrene and doesn’t sag. It isn’t the easiest filler to sand down because it sets rock hard, but it’s very fine when you do abrade it, so the finish is much smoother.
HB42 isn’t as cheap as a lot of similar products, but as this blog is about ‘the BEST filler for exterior wood’, then this is the one I recommend.
The Best Epoxy Wood Fillers
This is the most expensive option on the list, but repairs made using epoxy fillers will last decades. The material acts as a strong adhesive as well as a filler, it expands and contracts with the wood, you can even bang a nail into it, or screw a screw.
You should remove paint around the repair before you fill when using epoxy fillers, then prime the bare timber with a stabiliser like Oxera Easy Mix to ensure the best surface on which to work.
There are three main brands of epoxy wood fillers in the UK. Repair Care, Timbabuild, and Oxera, and they’re all similar. I’ve been using Oxera for about two years now because even though they represent very good quality, they’re cheaper than the others because you’re buying direct from the manufacturer. You should use the 1-hour for small repairs and 4-Hour for larger repairs.
You will need to buy the application gun to apply Oxera 1-Hour, but the 4-Hour product is available in pots, so you don’t need expensive tools.
The Best Exterior Decorators Caulk
I’m not going to go on for ages about the best caulk to use for exterior wood, as it isn’t the most riveting of subjects. The one I use is Red Devil One Time from Ciret, which is possibly more out of habit than anything else.
Years ago, I’d just use any exterior caulk, but I found that a lot of them failed over time. I’d drive past jobs and see my paintwork splitting, which as a professional, was hard to take.
Red Devil One Time doesn’t seem to fail, so I stuck with it. I haven’t used any other caulk for exterior work for 4 or 5 years now, and I don’t intend to. There are probably other caulks on the market that do the same job, but I know I can trust this one.
The Best Glazing Sealant or Exterior Windows
There are two different types of glazing sealant available: traditional linseed putty and the more modern hybrid polymer type of product.
Toupret Putty Mastic is the best linseed oil putty I’ve used. It has a good consistency, it’s easy to shape, and isn’t sticky. Click here for more info.
However, I believe modern hybrid polymers are better. They’re quicker to use, adhere better, make a better seal, you don’t need to prime wood before applying them, and you can paint over them after an hour.
I think most of the hybrid polymer glazing sealants are similar to be fair, but I use Oxera. It seems slightly easier to use.
FAQs
How to fill large gaps in exterior wood?
Dig out any rotted wood, remove paint from around the repair, then prime everything with epoxy stabiliser or wood hardener. If the repair is very big, then you can pack it out with off-cuts of timber. Then fill the remainder of the hole with Oxera 4-hour Rebuild Filler.
Can you put wood filler on rotted wood?
All rotted wood needs to be removed before filling the hole ideally. Otherwise, your repair will not last.
What is the difference between wood putty and wood filler?
Putty is often used as a glazing sealant. Wood filler is used to fill holes.
How to stop wood rotting outside?
Dig out the rotted wood, allow the exposed wood to dry, then apply a generous coat of wood hardener.
Will vinegar stop wood rot?
Surprisingly, yes. Or it’ll slow rot down anyway. Vinegar kills the fungus that eats away at the wet wood. However, vinegar isn’t a permanent solution. I’d suggest using wood hardener instead.
How do you test for wood rot with a screwdriver?
Just push the screwdriver into the wood. If there’s rot, the wood will just collapse under the force of the screwdriver.
Final Thoughts
I think I’ve given you all the information you need to choose the best filler for exterior wood. We have a separate blog on how to fill rotted wood, which you can view by clicking here.
I can’t stress how important it is to choose the correct products when carrying out this type of work. If you don’t, or you don’t carry out your prep properly, then all the work you do will fail withing a few months, and you’ll be back to square one.
What Other Decorators Think
Two-part filler if it’s a deep hole or on a corner. Then use Toupret Wood Repair fFller for smaller holes. I use the Toupret Ready Mixed Wood Filler for pin holes or just to fine fill. With the movement cracks on doors, I first fill with Toupret Skim Flex, then over fill with ready mixed wood filler.
I use Repair Care for exterior wood.
I used to use Ronseal 2-part wood filler a lot, but I recently turned to the Toupret Ready Mixed Wood filler and it’s really good. As easy to apply as their TX110, but better as it’s already mixed and in the heat of the last two weeks it dried quick. It sands like any of the Toupret powder fillers, really well, unlike Ronseal, which always seems to leave a small lip somewhere. This is a tennis clubhouse which had quite a lot of filler applied and all in the Toupret Wood Filler.
For small nail or screw holes I opt for Toupret Wood Filler. For something larger or for areas subject to movement, I us and epoxy resin system like Oxera Rebuild Resin. Other good resins are available, but Oxera’s price point is a winner for me. I’d probably say Oxera is the best filler for exterior wood if I’m completely honest.
It depends on depth, but I tend to use Ronseal 2 part or Toupret wood filler.
Ronseal 2-pack filler for me. Easy to rub down, no-cracking, good price compared to quality and just nice stuff to work with.
Any two-part filler, or if I’m feeling flush, I will use the Repair Care Fine Fill 👌
I used this for the first time on job I just finished, and I love it! It’s a game changer, and a lot better than 2-pack wood fillers.
It dried hard, it’s easy to sand, no sink, covers well! Toupret 💙you!
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