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Is MDF prone to warping?


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Hi, i've got a sheet of 0.5 cm MDF is my attic that I'm planning to use as a baseboard top. My question is, is MDF prone to warping, and could I use it for baseboards with sufficient framing?

 

I know this a bit of nOOb question but I'm young and I haven't had much prior experience in woodwork. smile.gif

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All timber is susceptible to movement, ironically it is more prone to do so once it has dried compared to when it is "green". The important factor in deciding what to use is what variations in humidity will the baseboard face. Will it be used in a centrally heated room and never taken out, or will it go to exhibitions etc. As for your MDF I would steer clear of using this material for baseboards in any capacity. Because it is a composite material any movement can be unpredictable.

 

Start off on the right foot by building from good quality plywood. If you already have a frame build and are just looking for a top - invest in a sheet of decent quality ply.

 

JD

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MDF is prone to warp unless it's really well braced. 5mm MDF is a bit thin for a baseboard top. Good quality ply - known as Birch Ply - is very suitable for baseboards. My original layout, with 18mm MDF, had to be scrapped due to warping of the MDF even though it was well braced. Now I use 9mm Birch Ply and I've had no such problems since. A good timber merchant will sell an 8x4 board of this ply for about £30 and should be able to machine-cut it to smaller boards of your choice. And ply is much lighter than the equivalent thickness of MDF.

 

Don't skimp on the baseboard as if problems arise they're often very difficult to resolve once the layout is down.

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All timber is susceptible to movement, ironically it is more prone to do so once it has dried compared to when it is "green". The important factor in deciding what to use is what variations in humidity will the baseboard face. Will it be used in a centrally heated room and never taken out, or will it go to exhibitions etc. As for your MDF I would steer clear of using this material for baseboards in any capacity. Because it is a composite material any movement can be unpredictable.

 

Start off on the right foot by building from good quality plywood. If you already have a frame build and are just looking for a top - invest in a sheet of decent quality ply.

 

JD

 

Okay thanks for your help. I'll have a little think about it.

 

EDIT- After seeing the above post and thinking a bit, I guess Its going to have to ply. The advice is much appreciated :)

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MDF has the moisture absorption of a sponge and the structural integrity of Weetabix...avoid.

 

Whilst I'm no 'Woodworking Wizard' the basic rules are to make sure whatever timber you use is stored in the area you are going to use for construction for a day or two before use - to stabilise the moisture content - and to seal the wood with paint/varnish or whatever as soon as possible after assembly, to prevent changes in the moisture level - these changes lead to warping.

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Im in a similar position to this gentleman I used plywood for my baseboard tops on a previous layout but without suitable bracing. The tops are still in excellent condition however have warped due to the lack of suitable bracing.

Next month will see contruction of my first serious layout (Im in competition with my father) I plan to use a ply top again but with much more 2x2 hardwood? bracing underneath. As the layout will be displayed and used outdoors (weather permitting of course) I was thinking about painting the wood before progressing to another on top. Is there any particular kind of paint that is going to keep the wood good for a long time?

 

Regards

 

Bluebird.

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If you need thin material for the baseboard tops then go for 6mm ply rather than 5mm MDF. As well as a couple of home layouts I have also built a few of show layouts and I go with 6mm ply tops braced out with 3"x1" softwood battens - light for portability and very robust. Due to ply being a much harder timber I do pre-drill my track pin holes as it is frustrating trying to drive pins in and having them bend & damage sleepers. I am also a big fan of cork underlay to reduce track noise but that is a personal choice.

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Most problems to do with warping are to do with poor and inadequate framing.

 

MDF is no worse than ply for warping unless you get it really wet, then the fibres of MDF begin to "blow" and it just loses its structure.

 

The support framing should consist of straight spars and diagonals. It should be self supporting in all directions and rigid. If you use the baseboard top to add strength in one dimension you will be applying pressures to the top which ultimately can fail and result in a twist being introduced.

 

All of this adds weight to the project - that may not be an issue for non-portable layouts but is a very serious consideration for portable or show layouts. If a layout is being designed to be really portable for expos - remember that those who lift it in and out of vans/cars and carry it across rainy car parks, up stairs, and into big halls may not hold your frame at the strongest point and the whole frame may be subjected to twists and collisions that were not originally designed in.

 

If you are stating out from scratch consider an open frame design. This gives much more scope for building in contours and changes of level than the tradition flat board.

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Most problems to do with warping are to do with poor and inadequate framing.

 

MDF is no worse than ply for warping unless you get it really wet, then the fibres of MDF begin to "blow" and it just looses its structure.

 

 

Most problems to do with warping are to do with movement in the timber caused by humidity, including the framing, as incidentally are most problems incorrectly linked to track expansion. Timber framing will only move in one direction, lengthways, ply adds advantages because it is constructed tessellated so give resistance between layers. MDF is considerably worse for warping and I'm afraid that is just the facts with the material. It has advantages in other ways. The question was not related to soaking the material but to the normal use for a baseboard - in which case ply is considerably more stable, especially good quality.

 

J

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Most problems to do with warping are to do with movement in the timber caused by humidity, including the framing, as incidentally are most problems incorrectly linked to track expansion. Timber framing will only move in one direction, lengthways, ply adds advantages because it is constructed tessellated so give resistance between layers. MDF is considerably worse for warping and I'm afraid that is just the facts with the material. It has advantages in other ways. The question was not related to soaking the material but to the normal use for a baseboard - in which case ply is considerably more stable, especially good quality.

 

J

 

Agreed, even in this day and age folks seem keen on adding more heavy bracing than a coat of paint though!

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If MDF is so bad why is it the modern material of choice for just about everything?

 

Just curious.

 

It's easy to cut I suppose; useful if you're turning a 2 up 2 down in Cleethorpes into a replica of the Palace of the Sun King with only 20 sheets of MDF and a jigsaw...

 

I honestly can't think of any other advantages over ply, maybe cost?

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If MDF is so bad why is it the modern material of choice for just about everything?

 

Just curious.

 

We have refurbishments using mdf for a whole load of stuff. It's great until it gets surface damage or water gets into the core, then it looks terrible. It's used because it's easy to use and cheap.

 

And baseboards can get wet - water based paints for one,

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If MDF is so bad why is it the modern material of choice for just about everything?

 

Just curious.

 

It can be machined extremely accurately. That is why it is used for mouldings such as skirting boards and door facings. It can also be coated with acrylic to give that gloss white appearance. Great until the first time the central heating goes on and then eeehhh. Joking apart it can be worked in the same way as very expensive timbers used to be.

 

J

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My fiddle yard is partly MDF - its thicker and heavier than the ply for the main layout but it was an awful lot cheaper. So far it has behaved but worst case relaying the fiddle yard isn't a disaster and its a useful experiment.  Mind you I've also got a microlayout on chipboard which I wouldn't recommned but which (owing I think to having been pretty much drowned in polyeurathane varnish has remained stable with only minimal framing. 

 

 It's worth pointing out too that bad and crap framing wood is as bad as none because it will warp the baseboard quite effectively. You can go too far the other way as well. I had some very cheap oak offcuts I used to frame one board. Granted the baseboard will still be rock solid and true when I'm in a box but boy is it heavy 8(

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If MDF is so bad why is it the modern material of choice for just about everything?

 

Just curious.

 

Various reasons already quoted - another, according to the building trade - is 'because it's more stable than timber' and generally that is true and helps to explain its popularity with the building trade. Provided it doesn't get water into it it is extremely stable and far better than ordinary timber. All our internal doors are mdf faced and haven't suffered any warping (as yet) since the house was completed a tad over 3 years back - and that's a new house with hundreds of gallons of water in the plaster and brick and block work let alone the floor screed etc followed by forced drying-out using dehumidifiers. In the same period even 'expensive' stock timber doors would have done something - as a couple of our softwood door frames have.

 

I've got many year's worth of my magazine collection sitting on mdf shelves in the attic - o.k. so the shelves have only been there a year and are sealed with two coats of the right sealant but thus far no signs of any bending or warping, and we all know how heavy 50 years of the 'Railway Modeller' is going to beblink.gif.

 

I have a portable layout in 4ftx2ft sections - living in an unheated but well insulated 'garage room' for a couple of years and before that for a year in a garage and before that for 3 years in an unheated shed - with the top surface of mdf on ply; no signs of warping at all.

 

Provided it is adequately framed and sealed it should remain stable in most of the climatic conditions likely to be found around UK indoor layouts but the dust from cutting it is hazardous stuff due to the resin/adhesive in it used to bond the material during manufacture and if you're pinning track to it pre-drilling of a pilot hole seems to be essential. Apart from the dust and its ability to blunt saws very quickly it's biggest drawback is that it is d*mned heavy.

I'm planning to use some of my stock of surplus mdf as shuttering for some concrete work next year and it will be interesting to see how it tolerates that; the last offcut I left outdoors lasted about 2 years before I threw it away as 'useless' and the two offcuts I've been stacking cement bags on in the garage have been there for a good couple of years with no apparent change to their condition.

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It's easy to cut I suppose; useful if you're turning a 2 up 2 down in Cleethorpes into a replica of the Palace of the Sun King with only 20 sheets of MDF and a jigsaw...

 

I honestly can't think of any other advantages over ply, maybe cost?

 

I find it blunts cutting tools quicker than ply, due to the resin content I suppose.

 

Keith

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I asked a local timber merchant if he could cut up some MDF for me and was politely refused as he understood that MDF dust can be carcinogenic. Any truth in this? ( anyway, for my wee indoor plank I'm still wedded to Sundeala, no problems at all PROVIDED it is primed according to the instructions on the wrapper.)

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My understanding is that MDF dust is most likely carcinogenic, but so is ply dust (both from the formaldehyde resins used to bond the fibres or layers) and even timber sawdust isn't all that good for you. (But then even towels can kill when swallowed in quantity...) My local timber merchant will cut any of the above (except towels) happily, since they have a table saw with suitable dust extraction hardware set up.

 

I don't use MDF for anything traditionally structural, but the thin stuff (4mm or below) is easily cut with a Stanley knife or similar and makes nice fascia boards. It needs painting (and drinks paint, so use a primer) for this, and if you get e.g. a dilute PVA run on the unpainted MDF it'll swell up locally and need to be sanded down.

 

Will

 

 

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There is some evidence that long term exposure to MDF dust can cause cancer, but then there is evidence that long term exposure to just about any dust can cause cancer as well. I've built lots of stuff using real woods, ply, and MDF, and if doing it often, you should always use a paper dust mask as many timbers are just as bad for you. If you're just building a baseboard every few years, then, frankly you shouldn't worry about it.

 

As for stability, if treated correctly, mdf is fine.The cause of warping is much more likely to be the cheap softwood framing used, as this moves all over the place at the slightest change in humidity.

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All wood dust is potentially carcinogenic in particular nasal cancer - which used to have a high incidence amongst wood machinists. Carpenters didn't produce the fine dust so avoided it. MDF does produce dust but also the resin (phenolic) is also a hazard

 

 

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I asked a local timber merchant if he could cut up some MDF for me and was politely refused as he understood that MDF dust can be carcinogenic. Any truth in this? ( anyway, for my wee indoor plank I'm still wedded to Sundeala, no problems at all PROVIDED it is primed according to the instructions on the wrapper.)

 

The dust produced when cutting MDF is officially rated as a carcinogen under the COSHH regulations (but then so is the dust from cutting hardwood) and the resin used in manufacturing it contains formaldehyde. You must wear a suitable dust protection if cutting it with power tools or in any quantity and if cutting it with hand tools you should wear a dust mask. The risk is reduced if power cutting tools are fitted with proper dust extraction.

The HSE are further investigating if the formaldehyde presents any other health risk - e.g. from handling or prolonged exposure but the current view according to one website dealing with the COSHH aspect is that any potential risk to that from the formaldehyde is lost very soon after manufacture and no precautions are currently recommended.

 

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Never had a prob with it in any way.

 

I staple cork tiles on top and build everything on top of the cork.

 

That way if you want to make any changes, scenery etc, it all comes up with no probs leaving a prisitine board underneath, bar a few small staple holes which you cant see!

 

Used tons of pva, neat and diluted as well as emulsion and poster paints etc.

 

So far so good. (7 years)!

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