Wood Filler Recommendations?

[Manalto]

I have a few projects running concurrently, all of which require some wood patching and I'm not confident in which product to use. Any suggestions would be greatly appreciated.

1. Coal shed (exterior) - there were some pieces added to replace rotted wood which I would like to blend in a little better, and a few small knot holes to fill.

2. Rafters in the sleeping porch - a few of the rafters are charred from fire damage. It's my understanding that paint will not adhere to burned wood, so I will scrape it away but in some cases would like to restore the shape of the rafter and fill the more conspicuous nail holes.

3. Stair risers - these have numerous dings and divots from multiple installations of carpet and subsequent nail and staple removal. I'd like to smooth these out; risers will be painted.

4. Stair treads - these are soft pine that have seen a good amount of wear. That's okay, but the holes left from nail removal I would like to fill in a way that will blend in with the rest of the wood.

[mjt]

I've had really good results with Abatron WoodEpox. I've only used it on surfaces that will ultimately be painted.

[phil]

Ive been using epoxy. I got some leftovers from floor finishing products, some is clear and mixed 1:3 with hardener, one is a crack filler , it is beige and mixed 1:1

if it is something like a knot hole you can bury a couple of screws in the area that gives the epoxy something to really hook onto.

sometimes what I do is saturate the piece with epoxy, then I mix in wood dust, I just use whats under my tablesaw, I've tried various proportions , as long as there is enough epoxy in there to saturate the wood dust it hardens up very solid and you can adjust the color by changing the type of wood dust, and you can change how fine the dust is. the stuff I'm using sets up in about a week It goes from something flexible to something quite rigid over the next week but it is dry to the touch and sometimes it is easy to trim it off while it is a bit plastic. or you can let it go hard and shape it with sanding etc.

It hardens up overnight I have an hour or so working time. different types of epoxy will harden at various rates. sometimes I want it to turn a bit like thick putty so it stays where I put it other times I want it runny.
you can solidify joints further by drilling holes and inserting epoxy covered metal pins or wood dowels. You can also combine fiberglass, fabric, cardboard mesh screen and various other substances to reinforce. even cardboard soaked with epoxy becomes a tough substance.

there are different formulations of epoxy, some hardens faster, all of what I have seen seems to act quite similar. whatever type you use refer to the manufacturers info they will tell you about the proportions and the working time.

epoxy unlike wood is non absorbent. it is somewhat flexible but it wont grow and shrink like wood so if you cover large areas you can get a situation where it traps water or where capillary action can pull water in between the epoxy and the wood and cause failure. wood can grow and shrink at a different rate and that can cause it to crack. Its best if you can get down to firm wood and a porous surface helps it hook in so you can drill holes and things to help it impregnate the wood. If you are coating plywood use new plywood. it will not stick to dirt or paint. you can use an angle grinder if you like to roughen the wood up.
indoors, for floors and things I use the water based putty, but dont use that outdoors or on windows. water based putty can turn back to mush if it gets soaked.

you can use the Mohawk blend all powdered pigments , or find similar from other makers and then you can adjust the color even more.

you can try other products. there is one you can get in hardware stores, that comes as two film cans and it comes in white or in wood color and you just mix it 50/50 , there are epoxy putties that you can blend much like Plasticine and the blending of it starts the reaction. If you just need a little then you can get the 5 minute or similar epoxies that come in a syringe with two tubes that dispense even amounts, this is handy. in some cases I use JB weld it is grey , quite similar.
epoxy wont stick at all to some plastics you can use that to your advantage for example you can lay plastic over top of the wet epoxy and rub it to get a nice shiny surface and pull it away after, or make a dam from a piece of plastic from bottles etc and tape it in place to contain the stuff if it's runny.
the temperature will affect the hardening rate. It may not harden in very cold temperatures otherwise the warmer it is the faster it hardens.
If you mix large batches. the reaction generates heat so that can cause even faster hardening times. in some cases dumping out the whole container and spreading it can give you more working time as you aren't concentrating this heat in confinement.
you can get little amounts at a hardware store. you can buy small bottles of A and B there too. If you want more I'd try a fiberglass retailer they will sell quarts, gallons even drums and of course the larger quantities come at much reduced prices.

for rafter tails you may find the water collects there. in some cases patching in a piece of wood may fare better, You can do a dutchman or a tongue and groove joint or dowels , or use various joinery methods to prevent the water getting between your wood and the repair.
often if you need to use a lot of epoxy you can fill the space with chunks of wood to take up the volume so you use less material.
If the rafter tails are rotted on the ends, that presents an issue if you just make them out of epoxy or albatron or whatever, what can happen is that the water runs to that place and it will get between the repair and the actual wood which may also be a bit punky.

you might be able to wrap the ends with something like metal flashing to stop water getting in there or maybe replace more than you first thought so the joint can be made up under the shelter of the roofing. you might opt to trim them all down and put the fascia board a bit closer to the building. If the rafter tails are out in the weather yes you can fill and shape them but think of the water getting between that repair and the wood it attaches to because it may fail there. you need to keep the water out from between the repair and the wood somehow, even painting it with tar might help. you could make a 1 or two foot piece and make your attachment point where it isnt' so vulnerable to the weather. water has a habit of getting between things if it can. it will find any crack and the issues grow down that crack between. If you can encapsulate it somehow this wont happen. you can paint overtop but dont try to stick epoxy over any painted surface or it will fail.

the problem with fixing punky old wood is you really need the repair to go right into where the wood is solid or you need to really saturate it. If water gets between and frost does it's thing it will not hold. It will not hold if it is painted , it will not hold if it is dirty.

bits missing on treads , sure just get it clean and dry and fill any voids. If you think it may fall out you can insert a screw as something for the epoxy to grab. If they are small areas just go for it and paint after.
If you have large voids think of cutting a piece of wood to fit the area and embed that in there even if it doesn't fit perfectly, the epoxy is forgiving that way, it can bridge gaps. If you bridge big gaps you want some fiber in there, that may be wood fiber or fiberglass or many other things. the epoxy is strong when it has the fibers in there. you can mold it and make things just out of epoxy in itself, you can add bright colors and die it to suit what you want. pouring it into molds is a totally different topic but it lends to that very well.

if you need to use plywood outdoors the marine grade is much better, the plys are held with waterproof glue, If water gets into plywood it will come apart but the marine grade stuff lasts a lot longer. if you encase stuff water can get int there somehow. If you put fiberglass or epoxy over the surface, make good drip edges and leave the bottom open then any water can leave through evaporating through the underside.

often this happens in boats, they use wood beams , then encase them in epoxy or fiberlass. the water gets in somehow, through some tiny crack.. and the whole beam rots inside where it is held captive. the only way to fix it is to cut it open and remove the wood member. often this happens to the transom of a boat , where an outboard may mount. or the main beams that run the length of the boat.

I've used epoxy with fiberglass, It will knit with the mat or roving and work just like fiberglass, I coated my front and back porch plywood with fiberglass resin and glass it works like an upside down boat and is impervious to water. It can be repaired by grinding out patches and doing more if you need to.
the cloth may bend sharply, the roving has limits, you canget different weights , differnet sizes of glass fiber. sometimes like around railings or near the house I put "cant strips", they are triangular strips of wood, they ease the curve for the glass and also act as a dam to prevent water running , for example between the house and the porch you dont want water between. I put triangular strips around the post holes on the porch so if water even approaches the post h the water following them down into the structure.
you can combine pre-made fiberglass pieces for example I incorporated a fiberglass drip edge to my porches so any water that runs off doesn't wet the structure. the perimeter is fiberlass the deck is covered in glass, for that i used polyester resin since it takes more.

I cant' speak for the albatron product, some like it , I prefer to just use what I have and I suggest looking at the prices of epoxy and just adding wood dust or whatever you feel like to adjust the texture and content of the solids. Its a bit like concrete, not very strong all on it's own , it gets its strength in the bonding so things like wood fibers or glass fibers or even metal parts can combine , similar to how gravel is a part of strong cement and not just fine sand. The strength is really in the combination of materials. There are a lot of different products on the market.

fiberglass boats are made with polyester resin, it is more stiff , less flexible than epoxy, If you do repairs to a boat epoxy is favored because it sticks better. In some cases you can use either. for example if you are encasing things. If you made a whole boat with epoxy it would be too flexible and too expensive.

if things are very delicate like an old carving you can use vacuum bagging , this utilizes a plastic bag and you put the part in there soaked in epoxy then suck all the air out, any voids release the air under vacuum and the epoxy really penetrates. this technique is often used if you do lamination, for example making a hockey stick or skateboard or something may use that process.

you can totally encase things. for example I fiber glassed my back steps this way and used fiberglass it worked similar to using fiberglass resin. I also mixed it with wood dust and tried painting it on or laying it on using a bondo spreader, both worked fine. you can combine walnut shells if you want a non skid , roughened surface. L eft the bottom bare so it doesnt' trap water.

I came across a place that sold concrete supplies, they were moving and some of this stuff was outdated or had dented cans and such so I got lots. Ive been using it for all sorts of projects.

I inserted a couple of pics so you can see the repairs I did on my chair. normally of wood pieces key together correctly, I use wood glue but in this case it had some previous repairs so I had to work with a gap that was not a perfect fit. You will have to ignore the cosmetics a bit. some of it is going to be covered with upholstery. yes there was a screw in there from a previous repair. some of the cared features were missing so I had to build those up. I'll use fillers and things for cosmetics but I use epoxy for the strength. what you see there isnt a finished repair but the arm of the chair is attached and quite strong.
If I were to fix a chunk of missing carving I'd want most of the repair to be structural so I'd use epoxy but like in this case, Its not acceptable or finished here but you can see how the big gap was filled where the rail meets the back of the chair. It actually had a big wooden dowel in there and that was part of the original joinery. you can just see that protruding out the bottom. I'll fill the screw hole with epoxy , but I will use wood fillers and things to fix up the cosmetics and hide the repairs. If I filled big chunks with wood filler they may just "chunk out" later but the epoxy and wood chips mixture is really strong stuff. I get the lacquer sticks in different colors, they can be heated up and dripped in to recessed areas then they can be polished like the finish of the rest. this isn't suitable to build up a part that maybe knocked but if you had too fill a gouge, like where something was bumped during moving and scarred , it works for that.

other parts of the chair ( not shown ) had chunks missing. what i did was mixed the epoxy and wood , wet the area with clear epoxy , waited until the wood fibers and epoxy mix got a bit like putty then I coud form it into the gaps I wanted to fill by packing i t with a putty knife while it was sort of in a plastic state. that way it doesn't' run all over being too liquid. with a higher concentration of wood dust it really looks like wood and you can sand it and finish it just like wood, when you start sanding it the pores open up if the chips are a bit larger so it is in effect "wood" mostly.

you can see how I used plastic to contain it then it can be sanded flat or else it takes the form of the plastic , Here you can see it is shiny with some wrinkles. I can sand it flat with a sander so it doesn't' look like plastic. the wood parts that do show like the repair near the arm will need more finishing. I will use lacquer sticks or wood fillers and hide in the repairs, its a bit of an art to get the surface and the color just right but I think you get the idea. I made the repair and got the parts lined up fairly closely , then later Ill worry about the cosmetics in a separate step.

for this I soak the parts with clear epoxy then pack any cracks and missing splinters with the wood dust and epoxy mixture, that way the epoxy penetrates better and binds to the rest of the mix all in one go. If I want even more strength I can drill holes, put epoxy in the holes and insert rods of metal or wood or what ever I want and they can be buried in there for added strength.

on the stringers for my stairs, sometimes they have an issue where you can knock off the edges , since they are cut in a zig zag pattern. and I broke one during installation . I found plates of metal that are meant ot me nailed down. I put those on either side of the stringer in there susceptible places and soaked the plates with epoxy and screwed the flat plates down also filled the joint. this adds a lot of strength especially since the flat plates and all the screws provided strength as well.
autobody fillers may have some similar properties, but they aren't really made for strength. with polyester you usually add a small percentage, like with bondo they will say add a 2" strip to a golf ball sized amount. If you do large batches the hardener is called MEC . with epoxy by comparison the mixing ratio may be 1:1 or 1:3 so the amount of hardener is significantly different. epoxy is roughly 3 times as expensive as fiberglass resin ( polyester resin) so if you have a large project where you need a 5 gallon bucket of it the price difference is significant. for the type of repairs you describe I'd lean to epoxy not polyester but its good to understand the difference.

If you want to delve into this more , search for the "wooden boat forum". some of those people restore old wooden boats and it comes into play. In general if you were to coat a whole boat in epoxy or fiberglass you can create a "boat inside a boat" and then see separation and issues. Some of those threads will give details , info and techniques you can transfer pretty directly and use in your attempts to fix rafter tails and such.

I have an old Victorian screen door, it is about 3/4 thick material , it was a bit wiggly. I drilled 6" deep holes at each joint and inserted some epoxy, roughened up the steel pins and soaked them in the epoxy and inserted them. the epoxy has no were to go in the blind hole so when you push the pin in it presses the epoxy into any voids it can find , then I bury the pin in there never to be seen again, encased in epoxy. I made that screen door really strong and you cant' tell the repairs are there since they are buried within. I'm not worried about rust because the metal is encased but you could use wood or brass if you worried about rust. in that case I used 3, 6" pins at every joint so I effectively buried about 6 feet of 1/4" metal dowel rod in the door and if you saw it you wouldn't be able to tell at all. If you tried to break through the door it would be quite strong like that. one would not suspect the pins to be in there. Just an example..

another tip. If you need to do repairs that are structural you can drill little holes through things with a thin drill bit. then use stainless steel wire. I use mig welder wire for this. then you can actually sew the parts together with the wire, and you can combine epoxy right into he repair, and you can hide the wire into he repair, it might look like a weld bead or you could make it below the surface if you needed it really hidden. this makes a really strong joint and it isn't very hard to do. Once the epoxy and the wire and all the holes work together it works very well. Ill do that for example if I have a cracked aluminum casting and I don't want to try welding it.. welding aluminum can be difficult. It will work on certain things but remember epoxy does not stick to flexible plastic. you can for example fix a broken pot metal part this way, for some things like that welding just isn't a valid option. using wire you can pull the parts into place and get them aligned before you involve the epoxy.

I got a bunch of canvas. Ive been considering making something like maybe a wood storage shed out of strips of 2x2 for the supports, then wrapping it in canvas , then painting it with the epoxy filler I have. It will harden and be quite strong and durable. once the canvas soaks up the epoxy it will become really tough and waterproof.

[phil]

another suggestion I thought was applicable was that someone here suggested using sarco putty for filling cracks between boards. sometimes the wood just opens up after it isn't installed on stairs and things and if you fill the gaps up then it helps stop the water getting in and delays further damage. I think I can use my epoxy in crack filler a similar way but maybe the sarco isn't a bad suggestion where you just need to fill a crack that you will paint over. of course this is no good for things like structural damage to the roundover on the edge of stairs but it may be fine on the treads if they dry, crack and open up a little, but not so bad as where you'd want to replace them.

[phil]

I was faced with similar in the way of lots of nail holes in my stairs. they were also painted red then grey then brown and the red was really difficult to get rid of.

I used a variety of sanders, belt sander, pad sander, even one made for tight corners. i put a roundover bit in my laminate trimmer and recut the roundovers on each tread to remove chipping. the trimmer could not reach the ends, so I did the last 3 inches manually by making my own hand scraper with a matching profile so i just scraped the roundover shape in to continue it near the ends where the router ( laminate trimmer) couldn't reach. a laminate trimmer is like router but has a smaller base so I found that could go an inch or so closer than the router could, because a router has a larger baseplate usually.

I found some of the treads a bit wiggly and glued the gaps a bit. on the edges of the steps where the roundover is , I drilled a few holes and drove screws down in to tie the edge into the other boards, I set the screws in deep by drilling holes the size of the heads in about 1/2" or so , then hid the screw heads with the tapered plugs.
here is a link to the plug cutters

https://www.leevalley.com/en-ca/shop/to ... PMEALw_wcB

I attempted to use a plug cutter. the way it works, you find a similar piece of wood, then cut plugs from it with the tool that fits in a drill. the plugs are tapered and you drill holes and insert them, there is a special bit ( a forstner bit) for that. to avoid chipping.

my findings were that although I tried to pick similar wood to make the plugs and lined up the grain pattern, I could still see them.

I then resorted to coloring my putty very carefully. for cracks and things I inserted wood slices. I found it easier to hide the marks with putty and also found that by smearing the putty in places where the red was hard to remove, then sanding I could sort of bury any red left under the putty. this saved a lot of nit picking at the red paint specks.

my suggestion is to use water based putty for that and to get some "blendall powders" or similar and carefully test the colors. the target is to get the putty to look like the wood with the finish applied. so you really need to just do a few , let it dry sand and put some finish on then look at the color and adjust the batch or maybe two or three batches until you get the colors just right. then when you do try to use them , mix them loosely so that the putty you apply isn't just one tone. once the color is just right they will be close to invisible. with fir it alternates between a more yellow color and a more red color. so try to replicate either color rather than trying to find a mid point.

if some of them show after sanding then you can take a thin tool like a needle or a knife and a ruler and scratch lines going with the grain, then refill with putty. that way you can make grain lines. if any putty isn't matching to your liking, just dig a little out and refill that area. you can use masking tape with holes punched in it , drop that over the nail hole, fill and pull the tape leaving the putty a bit proud of the surface that way you can press the putty right into the nail hole without spreading it too much around the hole where you dont need it.

if you put tape either side of a crack you can do similar and press down with a putty knife driving the stuff right into the crack then pull the tape.

since the wet putty is left proud of the surface as it dries and shrinks you wont be left with a hollow that you need to fill a second time. so leave it a bit proud until it dries and you wont be refilling them all to make up for the shrinkage. that little bump you leave will sand off really easily when dry.

if you wanted you could use the kind of putty that smells and hardens by evaporating the solvents. its a bit more stable and dries faster but the issue is that you need to protect your main batch from drying up. The water based stuff is much easier to control. just keep it in a zip lock bag with a damp towel and it wont dry up on you if it does you can re saturate it with water.
just dont be tempted to use water based putty on stuff that gets wet or goes outside. Its fine on the stairs, you'll put a finish over-top of some sort anyway.

a quick and dirty way is to putty the whole surface and then sand. the problem then is that you cover more than needed with putty and you need to sand a lot to remove it also it is hard to really drive the putty down into cracks and nail holes that way. It may work on surfaces where you can really do a heavy sanding. Its faster to trowel putty over the whole floor and that may be good in some instances but not my preferred method. I'd rather take a bit more time mixing and applying the putty carefully, I think the result is better. If you go with your batches of color you will notice some boards are darker , some lighter and adjust as you see fit. Just make yourself a little palette of about three colors and apply them artfully. monotone putty can look really horrible as it wont mimic wood as well because wood is usually not a very consistent tone throughout it's surface. once you hit the colors spot on you will hide those nail holes so well they cant' be easily noticed and they will dissapear.
Like with a lot of things when you do a perfect job of it , no one will ever notice your fine workmanship

another way to fill nail holes is with little sticks. I just did thousands of them in that chair I'm working on. what I did was cut some tapered slices of wood and then chiseled little tooth pick sized pieces of them. once I had a pile of "tooth picks" I dipped each one in glue and drove it in with a hammer. wit the chair I just didn't want issues with nailing because it was riddled with holes and I knew that may cause some to not grab so In that case I wasn't worried about the cosmetics, just making it stable again to nail to . you can do that but then you will see the end grain. I do this when removing hardware, easier to plug the holes then my screws grab better. sometimes if you want to move something over just a tad and there is already a screw hole it helps to plug the hole and start fresh. same if the hole is sort of stripped out. you can just use tooth picks but I like making my own , that way the larger end is a little larger than a tooth pick. the grain needs to be in the end to end direction of course.

[Gothichome]

James, the standard for filling and shaping is Albatron, for the nail holes I would just use a good quality air dry filler.
A proper fix for your burnt wood be a of a scarf if it just a surface repair. Not hard to do, a little more thought needs to be put in to scarfing if any of those beams are load bearing.

[1918ColonialRevival]

Another recommendation for the two-part epoxy filler from Abatron for use on any surface that is going to be primed and painted. It's not cheap, but as the saying goes, you get what you pay for. I can attest to its durability. I have a few areas outside where I applied it 10 years ago and it's held up fine in all the Mid Atlantic weather.