Will MDF expand ??

Old 06-23-08, 05:09 PM
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Will MDF expand ??

I would like to build some stormwindows out of MDF.
I'm thinking of taking a sheet of MDF and cutting out the openings for the glass and then route a rabbit for the glass to set in. Is MDF stable enough to do this without the wood expanding in the window frame? I'm looking for a easy way to make these windows will the tools that I have.
Old 06-23-08, 05:48 PM
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MDF, although touted for its dimensional stability, is affected by expansion and contraction, although minimal. It is affected by temperature and humidity, but considered to be one of the most stable building materials. The fibers within the board have the ability to expand and contract without distorting the board.


MDF should not be exposed to water. The fibers will absorb moisture and swell. It performs best at humidity levels between 35-55%.

There is, however, an exterior grade of MDF that can withstand the elements that is now available and can be used for window parts. Recommended uses include:

- Road signs
- Advertising and business signs
- Shop fronts and fascia panels
- Garden furniture and playground fittings
- Boat cabin linings
- Exterior mouldings
- Sports score boards
- Shelving in open storage areas
- Exterior door panels

Exterior grade MDF may not be a stock item at the local building supply in the thickness desired, but they should be able to special order.

Because the exterior grade product is described as moisture resistant (that does not mean moisture proof), keeping the product sealed would be important.

Photo Credit: GreenWood WorkShop
Wood Storm Windows Constructed of Clear Wood Stock
Old 06-23-08, 05:55 PM
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Theres a different type of MDF as TP mentioned. I cannot think of the abreviation...saw "Norm" work with it. KEEEEERAP.

Yer not going to find it at any home Center...maybe a good lumber yard.

Still needs sealing of the cut edges.
Old 06-23-08, 06:20 PM
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Was it Medex? I am not aware of an anacronym.

The exterior grade MDF will run you twice or more than standard MDF. I would not use standard MDF for exterior applications. It can swell in interior applications where there is high humidity. Exterior grade MDF is 'moisture resistant,' but so is real wood, which must also be kept sealed to prevent prevent moisture penetration.

One characteristic of MDF and particleboard is the weight. I have loaded and unloaded truckloads of cabinets manufactured of particleboard, MDF, plywood, and solid wood. Solid wood was far lighter for a 125# girl.

Not a woodworker, although father was a carpenter, but I think that after pricing the exterior grade MDF that we would be far better off to buy real wood and any missing tool in cableman's tool box.

cableman, if you post what your tool inventory is for the storm window project, then perhaps Gunguy or Tim the Tool Man or someone can address your workshop needs.

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