MDF siding

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I’m currently working on the RGT Beach Bungalow. Exterior is milled “siding” with the clapboards already prepared in MDF. My first DH was the Greenleaf Arthur, so the MDF was a new situation for me.

I carefully sanded the milled clapboards/ siding with fine grit paper (working from 220 to a finer grade) before the first coat, after the first coat and I’m sitting here looking at the second coat and not liking what I see. Is there any way to get a smoother finish? It still looks rough. The paint finish is thin coats of good quality latex paint from Home Depot.

If I have to sand it all off and try something else, I’ll do that!

I really appreciate the help on this forum. I’ve learned a lot from reading other people’s posts, as well as the responses to my posts.

Edited by Lita

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MDF does not sand smooth.  Spread spackle/ drywall mud/ joint compound over your surfaces and when it's thoroughly dry sand it smooth, wipe the residual dust off with a damp rag and let it dry thoroughly again, and you will have a nice, smooth surface to paint or wallpaper.  (I dislike working with MDF intensely)

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I am opposite to Holly - I like MDF. You should be able to get a good smooth surface. My suggestion is a good quality undercoat, sand with fine grit sandpaper, second undercoat if needed, another sand then two topcoats. Oh and use a matt finish paint.

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5 hours ago, shannonc60 said:

I am opposite to Holly - I like MDF. You should be able to get a good smooth surface. My suggestion is a good quality undercoat, sand with fine grit sandpaper, second undercoat if needed, another sand then two topcoats. Oh and use a matt finish paint.

Perhaps it's more accurate to say MDF doesn't like me.

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You may not like my solution:

paint stripper, thin coat of drywall compound, a sponge sander, coat of primer, two coats of latex.

Latex doesn’t sand well. It’s basically a plastic ballon on top of pitted wood. You have to fill the pits with the drywall compound before painting.

Maybe call RGT and ask them for advice.

 

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Hi Lita…….. I used MDF siding on my house.  I used a latex semi gloss.  Thinned it out some. Put on about five or six coats with fine sanding in-between each coat.  I made a set of sanding sticks. Take a popscickel  stick and cut it on a 45 angle, glue fine sandpaper to it and than trim off excess after it is dry. Was just perfect for the sanding.  came out perfect

Have patience.

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31 minutes ago, Bob Hood said:

Hi Lita…….. I used MDF siding on my house.  I used a latex semi gloss.  Thinned it out some. Put on about five or six coats with fine sanding in-between each coat.  I made a set of sanding sticks. Take a popscickel  stick and cut it on a 45 angle, glue fine sandpaper to it and than trim off excess after it is dry. Was just perfect for the sanding.  came out perfect

Have patience.

I trust Bob.

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22 hours ago, havanaholly said:

MDF does not sand smooth.  Spread spackle/ drywall mud/ joint compound over your surfaces and when it's thoroughly dry sand it smooth, wipe the residual dust off with a damp rag and let it dry thoroughly again, and you will have a nice, smooth surface to paint or wallpaper.  (I dislike working with MDF intensely)

Thanks so much for all the advice. I’m going to try Bob’s advice since I’m so far down this road, or maybe better yet, try it on a small section of a board or two to see how it works.

I will definitely spackle if I do another MDF house.

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I've painted it several times. Recently, on the Victoria's Farmhouse I'm working on. I went over mine with oil based Kilz first. Then I sanded that with very fine sandpaper. It's pretty smooth like smooth enough that I can run my hand over and it feel any little spot I missed in the sanding and fix it. I haven't painted it yet but have painted the Painted Lady using primer first as well on that one, and I feel it came out well. The primer is maybe more liquid than the paint so I think it might make a better first coat but I realize you are beyond that point right now. I'd keep sanding on it.

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Hi Lita …….. I was wondering how you are doing and if you tried to make those sanding sticks.

Silver Dollar Out

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9 hours ago, Bob Hood said:

Hi Lita …….. I was wondering how you are doing and if you tried to make those sanding sticks.

Silver Dollar Out

Bob, I was out of town 2 days this week but now I have a 3 day weekend and will be working on it tomorrow. Sometimes I feel like I spend more time thinking about what I'm going to do than actually doing it.

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Bob, your sanding sticks idea is good; I tend to buy packs of cheap emery boards and fold or cut them in half to get into tight places.

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