How much of overlap for lap weld

[csouth]

I need to do some repairs on toe board area of my floor. I know a butt weld is the method preferred by most, but since I'm doing this myself I need to use lap method. I wanted to know what is the recommended amount of overlap between the 2 panels?

[jlcustomz]

One of the biggest concerns with lap joints is corrosion between them. Weld through primer can help this. I don't generally use lap joints myself, but I'd probably do 1/4 to 1/2".

Another option here which would take advantage of using a lap joint is to use structural panel adhesive rather than weld. Get complete bare metal between the 2 surfaces & completely coat with the adhesive. Many new car panels adhere this way. This method helps to eliminate rust issues caused by welding (especially inside surfaces that can't be reach) & warping from heat. 3m #8115 is one I've used several times with great results, though there are other types & brands.

[csouth]

Thanks for the feedback. My plan was to use seam sealer and undercoat on the overlap area once finished.

[minendrews68]

I promise, rust and water will find their way. I too have used the 8115 some of the best stuff on earth in my opinion. This stuff holds most anything and as stated before will eliminate any voids between the panels. Do some reading up on it and see what you think.

[MonzaRacer]

use 8115 and stitch weld about every 6 inch. Trust me you wont be sorry. clean, prep, follow instructions and your install will live forever, seam sealers lately are getting cheap, especially the latex based ones.

[csouth]

use 8115 and stitch weld about every 6 inch. Trust me you wont be sorry. clean, prep, follow instructions and your install will live forever, seam sealers lately are getting cheap, especially the latex based ones.

I think mentally I just like the combo of weld and 8115 together...