Filling screw head holes in MDF and wood

[FrogParty]

I have hundreds of screw head holes in both MDF (skirting boards) and new timber (door sets) to fill and prep before painting. What filler do I use that will give good long lasting results and be easy to use?

The ease of dry wall joint cement is temping, but worried it won't last and tends to dip into deep holes needing a second fill. OTOH 2 part wood filler will last, but I find it difficult to use - short working time, harder to sand etc. What do the pros use? Any tips?

 

[opps]

Two pack filler is great but in time you will see the filler sitting proud of the MDF. Typically this may only be 0.1mm but it can become pretty visible. That it happens less with timber than MDF leads me to conclude that the MDF swells and pushes the filler out (albeit very slightly).

On timber I would stick to the styrene resin (2 part) fillers and on the MDF I would opt for red Devil OneTime. The downside is that the OneTime is quite soft which is a bonus when sanding though. To sand the OneTime, I would recommend 180 grit silicon carbide paper (using a sanding block to prevent cupping

Sanding the 2 pack filler, a random orbital sander or an orbital sander, preferably connected to a dust extractor.

 

[jcb208]

2 pack is proberbly best but next best will be tetrion filler which you mix with water and very easy to sand .The ready mixed like others is hader to rub down

 

[opps]

I really hate the powder fillers and only ever use them on plastered walls.

I have seen so many examples of them blowing on wood work. Additionally when filling MDf I would want a filler with as little water content as possible.

Sorry, just my opinion. However I do agree that the Tetrion premixed types of filler are a pain to sand

 

[FrogParty]

Thanks for the quick rsponses.

Two pack filler is great but in time you will see the filler sitting prouder of the MDF. Typically this may only be 0.1mm but it can become pretty visible. That it happens less with timber than MDF leads me to conclude that the MDF swells and pushes the filler out (albeit very slightly).

In my situation it is more likely that the MDF dries out and contracts leaving the filler sticking out. I have had that happen with holes in MDF window ledges that I filled with joint cement. MDF does seem to suck in any damp, and my new build is still drying. Going to stick a moisture meter on the MDF before I paint.

So it is 2 part then in the holes followed by orbital sander where it can reach, not looking forward to that job.

 

[opps]

You could 2 pack, leaving the filler just below the surface and then Red Devil to finish.

That way you get the strength of the 2 pack (plus the rapid setting) and then the ease of use of the softer Red Devil.

 

[jcb208]

We use the tetrion on woodwork on new build all the time due to ease and quickness,Going back after 6 months for maintanence yes the filler does pop a touch but have found this is the case of 2 pack as well.My reasoning is the MDF gets damp and then shrinks. have known MDF skirting mitres to shrink up to 10 mm as 9 times out of 10 theres no heating when there decorated.If its is your own place I would use 2 pack not wood filler which is really hard to rub down but Isoponp38 easysand which rubs down easy

 

[FrogParty]

So many holes to do that a slower drying filler would be fine, I'm not going to be back with paint until the next day at least. Easy to sand and less likely to blow/pop are priorities. Sounds like 2 part and ready mixed wood filler are both hard to rub down, yet car body filler is easier? The idea of finishing with something softer also attracts even if it complicates the task a little. Thanks for the tips.

Would it be good to get a primer coat on there and down the holes before filling? The skirting boards came primed, but the holes will be raw MDF, and the door sets are bare new timber of course.

The window ledges are raw MDF that got soaked during the wet plastering (bad choice of materials, but too late now). Keep changing my mind over what to paint them with. Want to get them dry and then seal, but every time I think they are finally dry they seem to shrink (hence dry) a bit more. Some say avoid water based paint, yet the purpose made MDF primer paints are water based. Some say only oil based paint will seal properly, but others say that the "microporous" nature of acrylic paint will allow any water out rather than trap it in. Now I have the filler popping too (only thing I have already filled, stuffed joint compound in the hole while fitting coving - idle fingers!!). Do I just sand it off (again), or dig it out and refill with something else non water based?