I'm planning to build a wall-to-wall desk in a brick alcove using wooden battens to hold the desk up. I'm doing this post to find out what size screws and plugs I need and if I'm using the correct materials — I don't want the desk to collapse.
ALCOVE
Here are the alcove with a temporary desk showing the dimensions. All 3 walls are brick. Unfortunately, neither of the corners are exactly 90 degrees.
DESK TOP
25mm MDF Board, Medium Density Fibre Board: 1200 x 600mm.
https://www.amazon.co.uk/gp/product/B07YM5JZX4/ref=ppx_yo_dt_b_asin_title_o09_s00
BATTENS
Planed softwood: 1800 x 34 x 34mm.
Is this ok? If not, I can get another piece.
SCREWS AND WALLPLUGS
What type and length of screws and wall plugs should I use?
How many should I put in?
EDIT:
Weight: the desk will only be a workstation, so it will only have keyboard, mouse, someone's elbows…etc
UPDATE #1
Thanks for the advice. I have decided to use 2×4 as the baton and attach with the 85mm fittings in the photo. Like this desk. Still need to get brackets or a metal stiffener.
QUESTION: Do I need a table leg under the right baton that sticks out past the wall or can it just float out past the wall?
Best Answer
Given the lengthwise span and the truncated support at the right end, I'd use cleats on the ends and two brackets across the back. 25mm MDF won't handle that load without a lot of bounce and some chance of collapse.
On the left, I'd use four 3/16" x 2-3/4" concrete screws with hex heads. Phillips heads are fine also, but they're difficult to keep from stripping, in my experience.
On the right, two or three such screws.
Across the back, either use screws every 20cm or so, or use two large steel brackets mounted with 3/16" x 1-3/4" concrete screws. Such brackets are unobtrusive to the user and don't catch the eye from across the room. The stability is well worth their use.
If you choose not to use brackets, you may find that you need a stiffener running lengthwise to support the front edge of the desk. It wouldn't need to be at the front edge--it could be back 1/3 or so. An aluminum angle or a tall wooden rail might do well.
Notes about concrete screws
I'm not familiar with what metric screw sizes are available, so I listed fractional sizes. The key is to get at least 30mm of penetration into the masonry.
With concrete screws it's critical to pilot properly. These don't grab like wood screws, where almost anything goes. If your pilot is too small they won't go in or they'll break off. If too large they'll immediately strip.
If you need to remove a screw, drill a new hole. As the threads cut they disintegrate the surrounding material, and a second run-in isn't likely to hold as well.