Absolutely! Extending a standard two-person garden bench design to comfortably seat four is a fantastic and manageable DIY project. The core principle involves scaling up the key horizontal components while maintaining the structural integrity of the original design.
First, focus on the seat frame and the top bench seat boards. You will need to significantly lengthen the main seat support rails (the front and back rails that run the length of the bench). If the original plan is for a 4-foot bench, aim for approximately 7 to 8 feet for four adults. Correspondingly, you must use more seat boards to cover this new length. Ensure you use the same thickness and width of lumber for a consistent look.
Crucially, you cannot simply elongate the frame without adding support. An extra set of legs in the center of the bench is essential to prevent sagging. This means you'll build and install a third leg assembly identical to the two end ones. This central support will carry the weight and keep your long bench stable for years.
Also, consider the backrest. It needs to be extended to match the new seat length. You may need to add an additional vertical back support in the middle for strength and to prevent the back slats from warping. Always use exterior-grade materials like pressure-treated lumber, cedar, or redwood, and apply a robust outdoor finish.
By thoughtfully scaling the dimensions and reinforcing the structure with a central leg, you transform a cozy two-seater into a perfect gathering spot for family and friends in your garden. Remember to always consult and adapt your original plans carefully, checking all load-bearing joints.