How to Use Interior and Exterior Wood Filler


You could throw away your old wooden furniture and fixings. Or you could mend it. These days, as the reclaiming, recycling and re-purposing revolution rumbles on and our throw-away culture dies a long-deserved death, more and more people are prepared to make do and mend than throw something perfectly good away just because it’s damaged, old or less than perfect. As a result we’re seeing a significant increase in wood filler sales. But why, when and how do you use them? Here’s our dummies guide…

Applying Wood Filler

Using Wood Fillers – What You Should Know

First, what exactly is a wood filler, AKA ‘wood putty’, ‘grain filler’ or ‘plastic wood’? According to Wikipedia, it is:

“…a substance used to fill imperfections, such as nail holes, in wood prior to finishing. It is often composed of wood dust combined with a binder that dries and a diluent (thinner), and, sometimes, pigment.”

Wood fillers can also be made of synthetic materials that will often accept wood finishing products. Sometimes, these are available in pre-tinted colours which cannot be coloured further, other than by painting over them.

You can completely hide holes and other damage using wood filling products, which is great news if a beloved piece of furniture, expensive wooden floor or exterior wood needs some TLC to bring it back to vibrant life.

About special Oak wood filler, Pine wood filler and more…

You can buy pre-coloured products especially for certain woods. Take Osmo Wood Filler, which comes in a wide variety of attractive colours designed to match woods like antique Oak, Beech, Cherry, Ebony, Pine, Spruce and even exotica like Jatoba wood.

Wood filler in action. Photo credit to: williefog

Four key ways to use wood filling products

The best quality products are incredibly versatile. You can use them in four key ways:

  1. To fill holes and cracks – You need a thick filler to fill cracks and holes in wood. But you have to prepare the inside of the hole or crack first so the filler sticks properly. Sand the inside of the hole of gap if you can and remove every speck of dust – vacuuming is ideal. Then use a putty knife to force the product into the hole. Smooth the top surface and once it’s dry sand it until you get an even finish, flush with the surface of the wood. You can use this method for wood flooring, furniture or anything else prone to cracking. Remember you can paint or stain the finished surface afterwards to make your repair invisible – just wait until it’s 100% dry first.
  2. To fix damaged furniture – Furniture demands some careful thought before you start. Firstly, are you mending the surface – a cosmetic repair – or a load-bearing part? The best product for surface repairs is a combination of thick and thin filler, with larger spots of damage needing thicker filler and smaller areas, a thinner product. To mend essential load bearing elements, a special wood hardener rather than an ordinary filler is probably your best option.
  3. To fill gaps between boards – You can even fill large gaps between your floorboards and skirting boards. There’s a specialist product for this called Bona Gap Master, available in a choice of popular colours including white and black as well as a load of natural-looking wood tones.
  4. Fillers that look like wood – When filling wood you need to ensure that the filler is 100% dry before staining or varnishing it. Filler gels are popular as they tend to keep repairs looking more like wood rather than a piece of white or coloured plastic. Filler gels work by mixing sanding dust, preferably from the wood being sanded and repaired, with a clear gel that binds the dust together. This forms a wood filler, that is partially made from real wood that can be stained, varnished or oiled. The thickness and consistency of the gel can be altered by adding more or less sanding dust, but the normal mixture is usually 50% gel to 50% sanding dust. Two popular filler gels that receive good customer feedback are Bona Mix and Fill and Fiddes Wood Filler Gel.

About Ronseal High Performance Wood Filler

Ronseal High Performance Wood Filler is a unique two-part product that delivers incredibly tough, strong and durable repairs to more or less any kind of interior or exterior wood.

Unlike some wood fillers, it can fill holes to any depth as long as you take it easy, filling half a centimetre at a time and waiting for each layer to dry before adding the next one.

It dries rock hard in just half an hour. You can drive screws into it, sand it, plane it, file it, bang nails into it and drill holes in it. You can paint, stain or varnish it. It kills wet rot and prevents it coming back. And when you use it with Ronseal’s special Wet Rot Wood Hardener, you can even mend rotten wood with it. Awesome! As you can imagine it’s an enormously popular choice with builders, carpenters, DIY-ers and craftspeople alike.

Practice makes perfect

There’s no reason why you shouldn’t do a few test runs on old bits of wood before tackling the real thing. The human brain is an amazing machine and it’ll soon build new neural pathways that make you more confident and competent. That way you stand the best chance of doing a great job.

Can I remove the filler once it’s dry?

Fillers are often harder than the wood itself. But you can remove them, and there’s some top guidance on the UK eHow site about how to do it.

Want to watch a video about how to use wood filler?

YouTube has the perfect video about how to use wood fillers…

Need our help with wood filler?

For more information about wood fillers and their uses, contact our team of resident experts who are always on hand to help with project advice and product recommendations. Alternatively, see our wood filler FAQ page which covers many of the most commonly asked questions about wood filler.

We love to see before, during and after photos of any wood finishing project. If you would like to share your project pictures with us and our followers, you can either send us some photos or share on our Facebook, Twitter, Pinterest or Instagram pages.

Other great blogs that discuss wood restoration

  • Getting Wood Door Renovation and Restoration Right
  • The Ultimate Guide to Wooden Beam Restoration

    1. Hi, by mistake I used interior grade Ronseal wood filler to partially fill a crack in the garden gate. It is exposed to all weathers but hasn’t rained yet so I wondered if I could add a layer of exterior grade filler over the top to seal it from the elements? I don’t really want to dig out the wood filler that I applied and which is now rock hard. Thanks, Tina.

      • Hello Tina,

        I do think this may be your best option if you can not get the interior filler out. It will be vital to completely cover the interior filler with exterior to ensure a better chance of adhesion and longevity. There will be not guarantees, but I can not see why it would not work. Perhaps just keep a regular check to ensure there are no issues or failures allowing moisture to get in. If you need any further help or advice please do not hesitate to get in touch via our contact us page.

        Kind regards Samantha.

    2. Hi

      I wish to paint my stairs. Having removed the carpet , I have gaps between my treads and risers, and also holes and small dents where the carpet was nailed and stapled in. Are the wood fillers and gap sealers on your site paintable ? Which would you recommend? Thanks

      • Good Afternoon Nageena,

        Thank you for getting in touch, we are seeing so many stair projects this year already, and we are loving seeing all our customers projects.

        I would say if you have long thin gaps to fill then you could have a look at the Bona Gap Master with a wide range of colours this product has the flexibility to deal with the natural movement of the stairs. And for any small holes that need filling the Ronseal High Performance Filler is another good option and can be painted, oiled or varnished over.

        I hope that helps and if you have any further questions please do get in touch via our contact us page.

        Kind regards Samantha.

    3. Hi

      I have unfinished newly installed mild oak stairs. I would like to fill small gaps & cracks prior to applying Fiddes hard wax oil. Any fillers that would work well with hard wax oil? Thanks, Denish

      • Hi Denish,

        There are a whole range of interior wood fillers that would be suitable for this. If you’re looking for a ready-to-use filler that can be used straight from the container, consider something like Osmo Interior Wood Filler. This comes in a range of colours so you can pick the one that best matches your staircase. Alternatively, fillers such as Fiddes Wood Filler Gel can be mixed with sanding dust to give you a more wood-like filler that can be stained if required, and finished as normal.

        I hope the above helps but if you have any further questions regarding you project or the products to use, please feel free to contact us at any time.

    4. Hi, we had our floorboards crewed down to stop the creaking before we lay our new carpet. I noticed there are some damaged floorboards with cracks and bit of wood missing, just wanted to ask which woodfiller will be best to take care of this for me?

      • Good Afternoon Mr Malik,

        It would really depend on the size of the crack and gap you have, if quite large the best option is sometimes to fill with a sliver of wood, which may or may not require gluing, and then use a filler to finish off.

        Often for projects like this I would recommend a Mix and Fill type product such as the Manns Trade Mix and Fill however sanding dust is required for this and I suspect as you are laying carpet that this is not an option.

        So as an alternative you could have a look at the Ronseal High Performance Wood Filler which is fairly versatile.

        For further advice please do not hesitate to get in touch with our friendly team via our contact us page.

        Kind regards Samantha.

    5. I have sanded and filled parts of my landing floor ready for painting. As the filler is white, and the floor paint will be yellow, how do i ensure that I get an even finish and that the filled areas don’t show look different to the sanded bare wood?

      • Good Afternoon Steve,

        Is the filler you have used one that can be over painted? If so the floor paint should cover it without issue a test area will give an indication of any potential issues. If you would like to get in touch via our contact us page with details of which products you are using, and I will be able to advice further.

        Kind regards Samantha.

    6. Hi, Ive just had a new staircase done and there are some fairly large nail holes that need to be covered up. I wasn’t sure what the best filler would be as I want to keep it looking as natural (mid/light oak) as possible after varnishing. Any ideas of which would be best? I was thinking about the fillers that you mic with sawdust?

      • Hello Sal,

        If you have some sanding dust from the stairs themselves this will make it match even better and will give a close finish to that of the wood. Although no filler is every an exact match the Bona Mix and Fill can give a close finish if used correctly.

        If you take a look at the product details and feel free to get back to me if you have any further questions.

        Kind regards Samantha.

    7. Hi,
      We had our wooden front door painted a few months ago. The decorator filled all the cracks quite carefully before painting but now the weather has warmed up (the door faces south) the cracks have opened up again.
      Is there a filler I can use that will fix this? Or will I just have to fill and repaint every year before winter sets in?

      • Hello Simon,

        Thank you for getting in touch, some fillers are more flexible than others but if your door is particularly prone to swelling and shrinking with the seasons then it could be an annual maintenance job that is required.

        You could have a look at the Cuprinol All Purpose Wood Filler this has some flexibility to it and can be over painted. Test areas are recommended.

        But for further advice please feel free to get in touch via our contact us
        page or give us a call on 01303 213 838.

        Kind regards Samantha.

      • Hello Graham,

        I could not recommend this, although you may find that it is okay depending on how exposed the area you are filling is and what you are using. A test area is going to be the best option. You can email me with more information to should you have any further questions.

        Kind regards Samantha.

    8. Hi we are in the process of putting faux beams in our living room/kitchen areas. The main beam or spine had to have about 2 feet attached as the beam itself was not long enough. Where the two meet however finds gaps on three sides and it looks like they are not square with each other…is there a wood filler to put on the three sides so it looks like one cohesive beam??
      Hope you can help
      Thank you!!

    9. Hello,
      I’ve just had a very old door internal dipped which has come up beautifully, but there are now large gaps either side of the lower inset panel, presumably from warping due to the dipping, although remnants of old filler were lurking in the gaps too. I don’t really want to paint it as the grain is so pretty so caulk is out. Any way I can fix it up for varnishing?

    10. Hi, I am trying to give a quote to repair and make good a set of oak doors and frame but where they have not been treated for such a long time all the surface is silver grey which I think I can treat but my main concern is all the fine cracks all over the surface which I would like to fill and sand back to a smooth uniform state so I am looking for a filler that can be applied easily and sanded back the same do you have any recommendations please.

      • Hello Dale,

        There are a few that could be considered. The Osmo Wood Filler is great for small areas and has a good range of colours available to match how you intend to finish the door. It is a ready to use paste like consistency. Osmo Wood Filler will accept wood finishing products such as Osmo Wood Oils. It will inevitably look a little different to the surrounding wood but the difference is minimal.

        Alternatively, for minor scratches and cracks the Wax Filler Sticks from Morrells are a good option and easy to use.

        If you have a read up on those two and feel free to let me know if you have any further questions, I am always happy to help. And if you need help to choose a finishing product for the door, please let me know.

        Kindest Regards Samantha.

    11. Hi

      I was looking a bit of information a 6 to 7 inch layer for laminate wood floor has lifted off and was wanting to know if there is a quick fix solution rather than having to replace the whole floor?


      • Hello Deborah,

        I am sorry but Laminate is not my field and you may be better checking with your supplier to see what they can suggest. We have a variety of Wood Fillers that may be an option. You could find one that is a colour match and suitable for the measurement of the area effected but I can not guarantee that this will work. Sorry that I can not give a more definitive answer.

        Kind regards Sam.

    12. hi, we have been sanding the treads of our stairs, now stained it, we also sanded the risers as we wanted to paint the risers white, after just one coat, on just five of the risers, we noticed how bad the risers looked, prior to painting the risers, against the wood stained tread, we didn’t notice how bad the risers were, until we painted them white, only done one thin coat…….can I put wood filler into some of the areas of the painted riser straight onto the paint? Then sand a little bit to make it smooth? I’m so hoping we don’t have to take off the already painted risers, that would be a nightmare………so is it possible to risk putting wood filler into the grooves, dents etc? I love rustic wood, and now wish I had just stained the whole lot, as dents in stained staircases, to me look great…….please help, and what is best thing to do…thanks Jill

      • Hello Jill,

        Thank you for your inquiry. This is something new to us and having spoken to our flooring expert, I would anticipate that it would be okay to use a filler over the top of the areas that you have already painted. Its definitely worth lightly sanding the area and then doing a test, allowing the filler to dry and then applying paint over the top. This will let you know if the filler will firstly adhere to the undercoat and then if the paint will also adhere over the top. There are a couple of products that you could consider. The first is Fiddes Wood Filler Gel which you mix with a fine wood dust or Osmo Wood Filler. Both of these products take oils and varnish, and so I would suggest that paint should be okay. Hope this helps – Sam


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