Antique beds add style and class to your home, but might not be as large as you need. Antique beds typically fit a double- or full-size mattress, as those sizes were the only options available. If your bed was handmade, then it may not even conform to any standard mattress size. Before adding an antique bed to your home, you must convert the bed frame itself and make it large enough to hold a modern day mattress.
Measure the modern-day mattress you plan to use with the antique bed. This gives you the exact length and width your bed needs to be to work with the newer mattress and box spring. Keep the dimensions in a safe place until you're ready to use the measurements.
Buy converter rails from an online store or a mattress supplier in your area. Converter rails consist of a large, H-shaped piece with brackets on each corner. The brackets attach to the headboard and footboard of your bed and are strong enough to support a large mattress.
Mark the appropriate locations for the brackets on both the headboard and footboard with your pencil. This shows you where you need to install the brackets to fit your new mattress. The brackets are designed to slide into existing holes on modern day headboards, but also attach with a few screws.
Attach the brackets from the converter rails onto your headboard and footboard, if you have one. Place the bracket flat against the inside edge of your headboard or on your first marking. Push a screw into place, through the bracket and into the headboard and screw into place. Repeat on each corner of the headboard and footboard.
Adjust the width of your bed by pulling on the centre bracket. This bracket pulls out several inches to compensate for larger mattresses. Set the box spring on top of the brackets and check the height. Adjust the centre support as needed, to raise or lower the box spring. Top with your mattress once the height is high enough.
Converter rails are designed to work with both a headboard and a footboard. If your antique bed only has a headboard, you may find it difficult to use converter rails. Test the strength of the bed before using it. When you first lay the box spring onto the rails, sit on the bed and bounce around slightly, to see if the bed collapses or the rails move. If you have any problems, attach another screw into each bracket, for additional support.