DIY-Prefab

You will of course need to make a number of design decisions before you can finalize what you need in the way of jigs and fixtures. Also I think it is important to point out that you might be able to do just fine without any jigs or fixtures if your project is small enough. That is after all the basic way that stick built construction is done. The accuracy of the various parts is the responsibility of the carpenters. There are various techniques that framers use to guarantee accuracy on the job site. Most of the techniques are based on careful measurements. That is one reason why building a house on site might be more expensive unless perhaps you happen to be that skilled carpenter.

Since no particular design decisions have been made yet for this part of my blog I will need to concentrate on somewhat more general suggestions regarding how you might construct a layout table if you do indeed decide that one would be useful. Something I think I forgot to mention earlier in the section on design constraints was that some of your design decisions may need to be based on how much work space you do have available if you are prefabricating things offsite.

One key thing to think about when building a layout table is how high you are going to build it. Traditional framing is done directly on the floor of the house that is being built. There is no particular reason your layout table couldn’t be on the floor if that suited your needs. You could even put markings directly on your floor if you wanted to that would help with panel layout. One nice thing about building a new house that has a wood subfloor is that you can draw things on the floor. I have found that to be useful from time to time. It can be especially useful for determining angles of rafter cuts for example.

Traditional framing on the floor is also useful if you will be nailing the members together with a hammer. It can be useful to be able to hold members in place by standing on them while you drive nails. Also swinging a hammer from above your work is a fairly easy way to work. Nail guns that are used for framing are usually designed with an angle to them that makes if fairly easy to nail framing members together from above. They also are very easy to use if what you are nailing is right in front of you. So if you are going to be using a nail gun or if you will be using screws to assemble your panels you might want to consider having your table high enough so that you can easily nail through the sides of the frame members without having to bend over so much.

If you do raise the table surface off of the floor there are some other things to think about. For one thing it may not be convenient anymore to stand on frame members to help hold them in place while you attach them. If you will be using a hammer to assemble your panels you may need to have a way of helping hold members in place while you drive your nails. One technique for doing that is to create raised edges on your table that give you something to hold your materials against while you nail them. For example in a typical 2×4 wall most of your nails will be through the top and bottom plate into the vertical studs. You might want to have a cross member of some sort at each end of the table that you can push your frame up against. Of course it will need to be designed in such a way at to not get in your way when you are nailing from that end of the wall. Perhaps these brackets could be hinged so that you can move them out of the way when necessary.

Nail guns and screw guns are nice in that they do not disturb the placement of framing members as much when you are attaching them together. It is much easier to hold the members in place while you attach them than it is for nailing with a hammer. Brackets or ledges that hold members together might still be desirable however.

You are likely to be attaching some form of sheathing (most likely something like plywood or OSB) to your framework before you consider your panel completely prefabricated. So one thing to think about is how you will attach the sheathing in the middle of your panels. How long are your arms? Can you reach into the middle of your layout table to attach sheathing? If your panels are never any wider than 4’ you should be able to. What about if they are 8’ wide or wider? I suggest that you might want to make the height of your table low enough to make it easier to reach into the middle. You might even want to consider making it low enough that you can easily crawl out into the middle of the panel to attach sheathing.