Newbie Desk Design

[Russell_AH]

Hi everyone,

I'm looking to build a desk for my new room, and I'd like to get your opinion on the design before I go ahead and start buying/cutting etc.
The desk is to go along an entire wall of the room (approx 4.5m) and will be ~90cm deep (there is a sloping ceiling above the desk, so some of the space at the back will be unusable). I don't plan to have anything massively heavy on the desk, just a laptop, desktop (although the base unit will likely go on the floor), electronics and Lego .

I'm looking to make it modular because a) I'm renting, so at some point it will probably need to be moved and b) it's a loft conversion with a rather narrow 180 degree staircase.

The design will consists of 5 sets of legs supporting 4 spans of desk top.

The legs are constructed from solid timber glued and pocket screwed together (the large circles show roughly where the pocket screws will go). The dowels in the centre at the top will slot into the cross beams (visible in the 'bottom' picture). The small holes on the top surface will take dowels to hold the desk surface in place. I am considering using metal dowels and cam locks (as in Ikea furniture) to make it more secure instead of the dowels. You can see how the top will fit on in the "top" picture, and allow adjacent spans to sit on the same set of legs. The dimensions are approximate at this stage.

My main questions are regarding the choice of wood.

For the legs and cross beam, I'm considering 70mm x 20.5mm redwood from B&Q. I guess it will be easier for me to use the same type of wood throughout. Would this thickness be suitable? I think the 70mm width looks good aesthetically to me, although in the model I've used 24mm thick wood, not the 20.5mm think I'm planning on using.

For the top, I was thinking of 18mm plywood; is this a suitable material/thickness? Also, would hard- or softwood be better for this application? Are there any others you would suggest I look at? I am likely to paint the top black, would there be any need for any sort of edging?

Also, I'd like to ask about the supports:
Do you think the dowel joints would be enough to support the top, bearing in mind that this joint won't be glued to allow it to be easily dismantled? Should I think about gluing some sort of ledge/shoulder to the central supports of the legs to provide more support? Should I also think about adding a second or third cross beam? I'd like to not add one towards the front of the desk if i can help it to reduce the chance of me knocking my legs on it.

Finally, are there any thoughts on any other trouble I may run into? Regarding tools, I can see I would need a drill, pocket hole jig, clamps and mitre saw (or similar) to construct the legs/beams, plus a circular saw and straight edge to cut the top surface (although I may get that done at the store), plus a sander for finishing; is there anything else you think I'll need?

Thanks in advance .

 

[oakmitre]

Hello - I'm sure someone will come along shortly with some very good advice, but until they do .........

Looks like a nice design, but if this is your first project I would make it simpler. You can reduce costs by using solid thicker whitewood and it requires a lot less skill.

CLS 63 x 36 eased edge 2.4m lengths are cheap at B&Q or Wickes, you can spend time selecting straight wood. It is currently £2.98 per 2.4m length and if you buy 20, it drops to £2
http://www.diy.com/departments/cls-timb ... 507_BQ.prd

Your design is does not account for sideways motion.A back bracing is required, it doesn't have to be substantial but it will make a massive difference to stability. Even a single piece of old laminate flooring will do.

Regards tools, a mitre saw is helpful as it allows you to cut a square edge. Make a long repeatable stop block using a length of MDF or anything to hand, screw a block to the end of the MDF, it doesn't really matter is the height of the vertical posts is 731 or 732 or 729 instead of 730, but it does matter that they are the same throughout.Clamp down before cutting, ideally two hands on the mitre saw handle.

Circular saw as a newbie - NO. Get the store to cut any sheet material for you.

To make the desk withstand tremendous weight, then some simple triangle bracings using what ever you have ( thin MDF, ply ,old laminate) will do.

Do not underestimate the difficulty of lining up dowels with holes in the top. Get some 45mm dowels.Assemble the desk upside down and using a stop collar on the drill bit, drill a 45 mm hole, this will pass through the 36mm bearers and 9mm into the 18mm ply.25 10 x 45mm dowels are less that £3 on ebay.
http://www.ebay.co.uk/itm/HARDWOOD-MULT ... R_g0UZaIYg

Regards 18mm softwood ply as a top, it can work(but may not be flat), but it is very susceptible to grain raising, meaning it will have a rough feel using water based finishes. For the edge it is possible to edge band it using cheap softwood par from B&Q. You can plane it down using a hand plane. I have used PU glue to affix this, as I feel it works better on the edge of plywood.It does however require some clamping arangements.
http://www.diy.com/departments/timber-p ... 403_BQ.prd

Once plained down to within 1mm of the edge you can sand the entire surface.

I have attached some 'diagrams', and yes I have just come back from the pub.

 

[oakmitre]

Ref your question about plywood hard vs soft. The hardwood faced ply has a veneer of less than 0.5mm, there is no margin for sanding to level with edgebanding.

I have glued a piece of softwood b&q ply to a piece of the doorstop edging mentioned above, I will attach a photo tomorrow if I can.

The photo shows 1.Solid wood edge glued on. 2.Planed down and sanded to surface of ply. 3. Edge chamfered with a block plane,then hand rounded over with 220 grit paper.Waterbased floor varnish added.

You can of course get iron on edge banding, but on a desk a sharp corner can dig into your forearm and cause problems.

 

[Russell_AH]

Thanks for the detailed response. Based on your suggestions I've come up with a new design (using the cheaper wood). I've also added corner braces (to some corners to see what it look like with and without).

I've added the braces inside the frame rather than attached to the outside, would this still work? They're 18mm thick, assuming that they would be made from off-cuts of the plywood top. They'd be glued and probably screwed/dowel jointed from the other side (or is it not possible to drill/screw into the side of the plywood?). Are they necessary? My understanding was that a glued and screwed joint would be quite strong. From the way you worded it it seems that it might work without them, just will be stonger; tbh I don't really like the look of them. Would some sort of metal bracket also work (although I would need 20 if I just did the outside corners, 40 if I did all corners, so is probably not worth the money)?

Regarding the cross braces, I did consider this, however I felt that they might not be needed as the desk will butt up against a wall on either end (so it is surrounded on 3 sides by the wall). I assumed that this would prevent any lateral motion. I guess it would be "best practice" to include them though. Would there be any problem wit pocket-holing them and screwing them into the sides of the rear legs? This way I could add them after the desk in installed. I guess I wouldn't be able to reuse the holes in the legs if I have to dismantle the legs to move the desk, although I doubt I will need to reconstruct the desk so many times that I would run out of places to screw the beam in to.


What are the main concerns using the circular saw? I don't intend for this to be my last woodworking project, so I feel it would be good to get some experience with one. On the other hand, would a jigsaw be a safer alternative? I guess I'd still be able to use it to cut down sheet materials assuming I have a suitable straight edge to cut against.

I'm also not clear on the choice of wood. What is the difference between the wood I suggested and yours? I notice that the white wood you suggest is listed under constructional timber rather than finishing timber; I would assume that means it won't have as nice a finish, but would this not be a concern as I intend to paint it?

Finally for the top surface, are there any finishes I can use to give me a smooth surface? It will be painted black, so I'm not concerned about preserving the grain or anything.

That was a lot more questions than I had anticipated....

 

[oakmitre]

I'll have a go at answering your questions - these are just my biased opinions of course.

Whitewood Vs Redwood.
Redwood is superior for joinery, it machines better and can be worked with hand tools easier.
Since you are cutting to length and drilling only, it makes no difference.

The term 'finishing timber' is just a marketing term, it doesn't mean much.Below is a photo of a piece of unfinished redwood sitting on top of a piece of floor varnished whitewood.I prefer the less orange look of the whitewood.

36mm vs 20.5mm thickness gives you more safety with your pocket screws - you may be able to do them from above and below.

With regards to screwing and gluing,if you are glueing endgain to anything it is not really that strong.Think of wood as a box of drinking straws.Endgrain is the end where the holes are in the straws.

The triangular braces would make it much stronger - but they are just an option.I like the way you have added them to the back rectangle only.If there is wall support, then you may be able to get away without the back bracing,but the chances are the whole thing may rub on your rented walls.Also if you lift the top,for example a child lifting it or you banging your head when underneath,or getting the arms of a chair under it - then the sides (and then top) will probably collapse.Certainly without the back brace and just dowels in the top, a freestanding unit would collapse easily.The backbrace also combats wobbling across the diagonals.

Circular saws - you don't need one for crosscutting if you have a mitre saw.Let B&Q do the sheet cutting for you for free - let them keep the dust and the danger.There are videos on safe use on youtube, but I would wait until a later date before deciding if you really want one.

Jigsaws are not great for cutting straight lines unless you are skilled.When using a guide the blade quickly deflects and curves away from the path.Some people can do it and swear by them- I can't They also tearout the top surface.Again there are more expensive jigsaws which can reduce this.

I would buy 2 for £10 green handled Spear and jackson handsaws from B&Q - they are excellent they are usually near the woodyard and not with the other saws on display.You dont need the rougher red or blue handled ones imho.

With regards to paint on top.Well I don't like black
Probably better to put a question in the finishing forum about painting ply.

 

[nev]

A 1.2m span of ply, mfc or mdf will invariably sag over time so if it were me I'd fix a front edge (2x1?) to your top sections, glued and pocketed if you do not want screw heads on the top surface. Stagger the front edge if you like to interlock the tops.

Assuming you are going from wall to wall that should take care of any sideways movement but a diagonal brace across the rear sections wouldn't harm.
Triangular rib in the top rear corners may well be enough support if you don't like the look of them on show. Also wall/roof fixing at the rear would help any possible forward /back movement.

A visit to your local builders merchant or timber merchant (Lathams?) would probably be cheaper and have superior timber to B&Q.
Just call and ask for prices for P A R. (Planed all round) or P S E (planed square edge) 2x1, 3x1, 4x1, 2x2 etc. Note: These are the sizes before they are PAR so for example 2x1 or 50x25 is more like 47x22.
see here... http://www.idostuff.co.uk/sections/DIY/ ... n%206.html

Disclaimer: I'm in no way a qualified carpenter/ Joiner/ cabinet maker but everything I've made so far is still standing and solid

 

[Russell_AH]

I have some felt pads to stick on the ends/backs that should hopefully prevent any wall damage. I guess if I'm painting the wood, both red- and whitewood should be able to be sanded down fine?

I don't think that lifting of the top should pose too much of a risk as there will be a cross beam under the centre of the panel which will provide some lateral support without the top, and won't lift as it will be pinned in either end by dowels/cam lock dowels (although I will have to think carefully how I will affix the end piece as there may not be the clearance to insert the dowels into the end of the cross beam on the final piece).

Nev, I'll look into Lathams and other local merchants. Regarding drooping, would the centre crossbeam provide enough support, or are you suggesting adding more? It would be made of the same timber as the rest of the frame (so currently 38mmx63mm). These wouldn't be glued to the surface pieces, but I had thought about putting a couple of dowels in to pin them together to prevent any lateral movement between the crossbeam and top surface.

 

[nev]

...
Nev, I'll look into Lathams and other local merchants. Regarding drooping, would the centre crossbeam provide enough support, or are you suggesting adding more? It would be made of the same timber as the rest of the frame (so currently 38mmx63mm). These wouldn't be glued to the surface pieces, but I had thought about putting a couple of dowels in to pin them together to prevent any lateral movement between the crossbeam and top surface.

All the weight, little as it may be, from elbows, laptops, books, junk etc will probably be in the centre of the spans and at the front edge. Could be ok, but over time I'd expect it to sag a little, but i may be erring on the side of caution. Also I think an edged or thicker top would be more visually appealing.

Maybe this may give you a more certain answer... http://www.woodbin.com/calcs/sagulator/

 

[Shultzy]

You definitely need the timber on the front and back edges, it will sag over time. I would make 4 identical tables and screw the end frames together when installed. This makes construction easier, will fit around the staircase, and the cuts are all the same.. The third of the four can be adjusted to fit in the available space. If you glue and screw the end frames you won't need any reinforcing pieces unless you keep pulling you and the chair into position using the front of the table.

If you can't cut a clean straight line with a hand, circular, or jig saw then cut to within a couple of mm and trim to the line with a straight edge and a router.

 

[Russell_AH]

Ok, thanks for your help and suggestions all, I will have a think about how I will go ahead with this.