Window Sill: Solid Wood or MDF

[Beowulf]

Ok, my wife wants new window sills. She want to move away from the very ornate edge they have now to a more contemporary/modern look with complete square edging.

The question: is there a reason to use the now normal MDF/partical board stuff or should I just use solid wood? Does solid wood have a tendency to warp over time?

I'm sure it will be more durable, but I don't want warpage in a few years.

 

[The Cobbler]

MDF doesn't like water or condensation, I would not use it for trim or sills . it has its place but that's not in my house

 

[pablo94sc]

Mine are solid wood and show signs of warping. Maybe a composite?

 

[pmiranda]

Yeah, if you live in a place with winter, or have older windows, or could possibly ever have your windows open for a second in the rain... you want real wood. It might develop a slight bend, but it won't swell up and flake off like the crappy MDF shelves that the previous owner used in our utility room. Somebody spilled some liquid laundry detergent once and they're F'ed.

 

[Beowulf]

They are all MDF now and show no signs of swelling. However, I'd just like the idea of real wood.

I will also be replacing all the base boards as well. I'd like to use real wood, but have not seen square edged real wood trim that measures 3.25". Maybe I'm just not looking hard enough.

 

[risc]

MDO, flat and damn near waterproof.

 

[Beowulf]

what is mdo?

 

[Beowulf]

Got it,,

MDO is a panel that has a layer of hardwood veneer directly under the smooth resin (water resistant phenolic) impregnated cellulose fiber overlay.

 

[Cyberbear]

It's probably not commonly available any longer but solid redwood was always used for weather exposed wood. Solid wood varies with several factors; species, width of the board, cut (qtr. sawn, flat, or heart), humidity, exposure to sun, type of finish and whether done S4S or only the exposed surfaces, etc. These are all the things to be considered, which is why they've gone to man made products, but still no guarantee against warpage.

 

[shelteredV]

why not windsorOne? cheap, stays pretty straight, mills easy

 

[strutaeng]

I used finger joined primed pine from the home depot, 1X3, in a "picture frame." It turned out nicely.

Not inexpensive (like 3x more than MDF), but nice, straight and pre primed.

I would never use mdf for this, or any other household trim.

 

[Toolfool]

I regularly install miles of MDF trim in million dollar custom homes. If it's properly installed, caulked and painted with a quality paint it can look amazing and last a long time. Your caulk and paint protect MDF or wood from moisture problems. If you care to browse my thread (link below) you'll see a $1,500,000.00 home that was trimmed inside almost exclusively in MDF, even the columns. I also do miles of VG fir, Alder, Hemlock, Cherry. It's customer's preference.

 

[speed bump]

I used finger joined primed pine from the home depot, 1X3, in a "picture frame." It turned out nicely.

Not inexpensive (like 3x more than MDF), but nice, straight and pre primed.

I would never use mdf for this, or any other household trim.

I'm exactly the opposite, I despise pine and will never use it for anything trim related unless the application demanded a rustic pine look. I use Poplar for high traffic areas where the trim might take a beating and MDF everywhere else. It takes and holds paint with minimal prep work compared to real wood, machines easily and predictably, and doesn't warp.

With regards to the original question: I wouldn't use real wood unless you like prep work. If you are really worried about moisture you could use something like Plycem which is an outdoor composite trim but MDF is used in your application everyday without an issue.

 

[James-W]

They are all MDF now and show no signs of swelling. However, I'd just like the idea of real wood.

I will also be replacing all the base boards as well. I'd like to use real wood, but have not seen square edged real wood trim that measures 3.25". Maybe I'm just not looking hard enough.

If you have a planer/molder, or if you have a friend who does, it is possible to make any kind of molding you want. There is a place in Kansas city that makes molding bits to fit difference types of planers. You take out the planing knives, put in a molding bit and counter balancing weights, make a guide for the wood to pass thru the planer, and you get a molding exactly the way you want it. The really good part is, you can make the molding from whatever type of wood you want.

 

[theoldwizard1]

For just the sill, I would consider laminating some 1by PVC trim and then cut and route as required. It will NEVER rot !

 

[4495]

Anyone besides me think that the author of the original post meant to say PVC and not MDF?

I'd use PVC all day everyday for exterior trim.

 

[Beowulf]

Nope, I meant solid wood like maple, oak, poplar, or pine instead of MDF.

Now for trim I have thought of PVC for wet areas like bathrooms.

 

[glentre]

Do not use mdf for window sills or anywhere else it might see water or high moisture. Painting it will delay swelling but if moisture ever gets under the paint layer, it will swell. It will pick up moisture and expand not just a little, but a lot! It grows significantly in width, (thickness) not so much in length As a retired owner of an architectural woodworking firm, mdf (medium density fiberboard) has its place in areas not near moisture like moldings because it machines well, is dimensionally stable if not near moisture and is economical. Large sheets like 4x8's are super flat and good substrates for plastic laminate but not in kitchens. It also paints well. Particleboard also does not like water but doesn't expand quite as much as mdf. We once built a 20ft high town square clock for an interior atrium using mdf and it machined and took paint so well we made it look like real aged copper.

You might consider a similar product called mdo (medium density overlay) which some use for outdoor signs but for this application, we would use poplar. Clear sapwood if it's going to be stained but less expensive poplar with some heartwood if painted. It's a finer grained wood than pine, stronger, more stable and does not split or warp like pine. If you have good finishing skills, you can make poplar look like mahogany, walnut or any other species.

Glen

 

[maxpower_hd]

I was assuming the OP meant interior window sills. I've only used wood and never had any warping issues. Most of the ones I have done were stained though so MDF or finger jointed wasn't an option for me.

 

[Falcon67]

Interior and exterior on the old house I used painted pine when I replaced the old double hung windows.

 

[Milton Shaw]

I have seen marble or man made marble used for window sills. Once installed there is nothing else needs to be done except occasionally wipe them down with wet cloth to remove dust and dead bugs.

 

[4495]

Tommy Silva of This Old House uses PVC so I will use PVC.

 

[James-W]

Tommy Silva of This Old House uses PVC so I will use PVC.

If Tommy Silva uses it, it MUST be right.

 

[Kevin54]

I've used the pre-primed MDF and have had no problems whatsoever. I've done it to surround all of my windows in the garage, then painted with a good semi gloss paint.

 

[Beowulf]

Yes, interior of Windows and all trim.

I like the poplar idea.

 

[Beowulf]

Man made would be nice, but not in the budget.

 

[plout99]

Bought my house 16 years ago, all interior trim was painted. The misses wanted stained trim. I replaced all the window sills with pine that was stained and polyed have never had a problem with warping. The sills have survived 16 seasons of Ohio weather and two teenagers who have been known to forget to shut there windows when the rain is blowing sideways.

 

[Gerald O]

The interior 'shelf-like' trim piece at the base of the window is properly called a window 'stool'.
Usually the window sill, which is the bottom member of the window casing, is sloped for water drainage toward the outside. You can buy stool moldings that are milled with an angled groove on the bottom that is intended to match the angle of the sill that it will rest on, so that the stool sits level. I found that choices are pretty limited. I too wanted a 'squarish ' profile for some windows in my shop, so I had to end up making my own. Pretty easy with the table saw. Cut them from plain clear pine stock, but any clear wood type should do. You don't want MDF in this application for many reasons, one being that the edges are rough and don't finish well.

 

[Zeke]

I was assuming the OP meant interior window sills. I've only used wood and never had any warping issues. Most of the ones I have done were stained though so MDF or finger jointed wasn't an option for me.

And interior "sills" are properly called stools and usually sit over an apron. The sill begins below the stool and extends to the exterior. Sills are generally at 10º while stools are level with a beveled rabbet on the underside to fit over the heel of the sill.

At first reading I thought the same as others, that the OP was considering MDF on the exterior. The horror.

 

[BADSIX]

if your going to be painting them then i would use Poplar, it will hold up well and paints excellent. paint the pieces before you install and they should last a life time.
Jay D.

 

[rlitman]

The interior 'shelf-like' trim piece at the base of the window is properly called a window 'stool'.
Usually the window sill, which is the bottom member of the window casing, is sloped for water drainage toward the outside. You can buy stool moldings that are milled with an angled groove on the bottom that is intended to match the angle of the sill that it will rest on, so that the stool sits level. I found that choices are pretty limited. I too wanted a 'squarish ' profile for some windows in my shop, so I had to end up making my own. Pretty easy with the table saw. Cut them from plain clear pine stock, but any clear wood type should do. You don't want MDF in this application for many reasons, one being that the edges are rough and don't finish well.

+1 First guy here to know his terminology.

In a shop, clear pine makes for an acceptable stool, but clear pine is expensive, and the tight curvature of grain I see in most pine leads to cupping pieces (this is especially an issue when you cut clear pieces out of cheaper grades of pine). I'll use pre-primed finger jointed pine moldings for paint grade finishes. These tend to have fairly straight grain, but I've seen them fail at the glue joints that make MDF look like a better option for a window stool (but still a good choice for other trim work).

In a home, assuming you want a painted stool, I prefer poplar. It's much tougher than pine, and less likely to suffer from dents and dings. It also has a tighter grain that makes for a better painted finish than oak.

I've used the pre-primed MDF and have had no problems whatsoever. I've done it to surround all of my windows in the garage, then painted with a good semi gloss paint.

Pre-primed is a good idea, and a time saver. Just be sure to prime all your cuts before installation.

if your going to be painting them then i would use Poplar, it will hold up well and paints excellent. paint the pieces before you install and they should last a life time.
Jay D.

+1 I'm with you (and a few others). Poplar. Dry fit it, and then prime on all sides. For a window stool, I'll bed it in a paintable caulk during installation for a lifetime of use (prime the window sill first too).

 

[TheOtherChris]

I have seen marble or man made marble used for window sills. Once installed there is nothing else needs to be done except occasionally wipe them down with wet cloth to remove dust and dead bugs.

All of the window stools in our addition are cultured marble (like used in some shower stalls). It is impervious to moisture and very stable but you can't paint it.

 

[HenryAZ]

I've seen poplar used for exterior work, like fence rails on a split rail fence, and it sure rots easily if it is not kept painted or otherwise sealed. Yes it is harder than pine, but not nearly as resistant to the exterior.

For a window sill, either redwood, as previously mentioned, cedar or cypress would make good exterior woods. All three have natural oils in them.

 

[GTO]

Window Sill=outside
Window Stool=inside

Never use any MDF for exterior application.

 

[CTyankee]

I'm exactly the opposite, I despise pine and will never use it for anything trim related unless the application demanded a rustic pine look. I use Poplar for high traffic areas where the trim might take a beating and MDF everywhere else. It takes and holds paint with minimal prep work compared to real wood, machines easily and predictably, and doesn't warp.

X 2

Yes, interior of Windows and all trim.

I like the poplar idea.

 

[Norcal]

MDF is easy to work, and takes paint well that being said, I hate it for woodwork where there is the slightest chance of being exposed to moisture because the only fix is to remove it & replace it.

 

[greg13]

If Tommy Silva uses it, it MUST be right.

But what is Mike Holmes using?

Personally I only use wood.

 

[CTyankee]

I missed the fact that this thread is about 2 1/2 years old. Beowulf is still active here. Maybe he'll come back and tell us what he used and how it's worked out.

 

[Marctrees]

They are all MDF now and show no signs of swelling. However, I'd just like the idea of real wood.

I will also be replacing all the base boards as well. I'd like to use real wood, but have not seen square edged real wood trim that measures 3.25". Maybe I'm just not looking hard enough.

Tablesaw rip plain flat stock to make plain base.

Sand to take the sharp corner off.

Marc

 

[Marctrees]

Did not see post # 38.

Oh well.

Marc