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Exterior Door Construction for Harsh Weather Conditions
Question
These doors are facing all directions, north, south, east, and west. There are also subject to internal temperatures as low as 20 degrees C and external as high as 55 degrees C. These doors also are for villas by the sea side and the environment changes from dry to humid quite often. Humidity can reach 100%. These are specified as solid wood doors. In Bahrain, external solid doors leaves are usually deforming and are showing some cracks at the points where the various pieces of timber are joining. The finish, varnish or paint, splits (externally). This is usually considered a defect and there are always arguments on this subject at the time of handing over. Any help is appreciated if anybody has experience on how such door leaves, made of solid wood or looking as solid wood doors, (laminated, insulated, reinforced, etc) should be constructed so that these problems can be eliminated. We have to provide a minimum five year guarantee. Forum Responses
From the original questioner: We agree with your concerns and we can convince the architect to increase the thickness of the door. Before we propose anything we want to find a tried, successful method of constructing such doors. We want to avoid a trial and error situation. We are sure that this problem has somehow been resolved in the past so we do not want to re-invent the wheel if possible. From contributor J: To build them "as drawn" (and guarantee them for five years) requires fully engineered composite panel construction. Acceptable (and proven) construction of solid plank doors begin with quarter-sawn, boards, tongue and grooved and set together vertically. The whole thing is reinforced with horizontal and diagonal wood or decorative iron straps and fastened with through-bolts or rivets. I made a solid plank door once with concealed internal all-thread rods and no external straps. I didn't like it but it’s still together after ten years - teak or white oak (never red) and no lacquer finish. There is no "guaranteed" five-year clear wood finish (especially for Bahrain). The individual boards will positively expand and contract with the weather, so a renewable oil finish or Sikkens (Cetol) would be best. Sometimes you have to tactfully teach architects.
From contributor T: You've got to pin down the architect's terminology a little more on this one. Solid wood door could mean block lumber core, structural composite lumber core, or even particle board core is considered a solid core door in the architectural door business. If in fact they are veneered solid core doors, then you need to determine the orientation of the grain. It looks to me that your architect may be specifying a sketch-faced door. Marshfield, Eggers, Algoma, Mohawk, Streko, and others make them. Your problem is going to be the warranty issue. They are not for use as exterior doors.
From contributor J: These type doors are common in Europe, especially Germany. The exterior surfaces are usually veneer (sometimes 4mm thick) with various types of core. Thick tongue and groove planks are used on the outside faces if design permits. Your DT02 door could possibly be constructed with these. They do have a lightweight solid wood core called Tischler Palette that’s used sometimes. The Holz Handwerk trade show in Nuremberg that was a few weeks ago is a good place to see all these materials. I think this type construction would be difficult to build without access to the right materials. Some of the core material has to withstand boiling water for 1 hour. Highly insulated cores are a big item now. At the shows you can also find the new generation water base finishes that will last for your warranty period. We don’t have much of this available in the US without importing direct. A lot of German shops do work in Bahrain so you might have access to these materials. You can look into the DIN standards for door building. They have all kinds of rules for door placement, construction methods, materials and finishes for wood doors depending on roof overhangs, porches, latitude and direction of the door ECT. If you can read a little German, the book “Hausturen aus Holz” by Horst Kastner has a lot of information about this. This is an exterior core sample I picked up at the Nuremberg show a couple years ago. It has oak staves, chip board, and some type of hardboard with aluminum sandwiched between. This is just one of many styles.  Click here for full size image
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