MDF & pocket hole joints

[robgul]

Asking on behalf of a friend (honestly!) . . . she wants a simple shelf/pigeon hole unit her utility room - I've given her some ideas on design etc but as she's about 150 miles away she's asked a local chap to do it.

He's suggesting 18mm MDF with all the sides and shelves having pocket-hole joints (not sure whether he's gluing too?).

My personal view is to avoid pocket-holes and MDF for anything load bearing, even if glued .... be interested in other views . . . .

 

[TheTiddles]

Depends on the load obviously but it could be fine

 

[clogs]

unless she's storing lead billet I'd say it'd be fine......
with the corrct kit and screws there are very strong......the screws are hardend high tensile....
not the soft as Chineseseum ones that are around......

 

[AJB Temple]

Well - I take a contrary view. I think MDF is nigh on useless for shelves. People always overload it (heavy bottles of detergent, irons, etc) and it sags. It isa cheap job and a poor job. It doesn't cost a great deal more to do it properly with decent materials.

 

[Derek Cohen (Perth Oz)]

I would argue that all MDF requires is glue and clamps. No screws needed.

On the other hand, unless you add hardwood battens to reinforce the underside, it will eventually turn into a banana.

Regards from Perth

Derek

 

[robgul]

... I think it would make sense to lash out on ordinary grade 18mm plywood (it's going to be painted) for the small unit and use pocket hole joints in the absence or rebates/dados/grooves for the shelves - it wouldn't be much more in £ for the materials (about 40% more than MDF from the yard I use)

If I lived nearer I would have don the job myself . . . . but I have made her a "rustic" fruit and veg rack from pallet wood

 

[porker]

Looks like you are getting a range of views on this. I think MDF is appropriate like any other material if used within its range. Loads of kitchen cabinets are made with it as well as built-ins. Peter Millard has built loads of built-ins and wardrobes with it. I have used it a lot on built ins and bookshelves and use hardwood edging and / or a torsion box construction that is plenty strong enough. Agree that it is poor if unsupported and nothing looks worse than a sagging shelf so design accordingly.

Also found pocket hole screws strong enough, you just need to design it so they are not visible because they are horrible to look at. Ilike ply but getting a good grade seems hit and miss and if patched it shows through paint.

 

[robgul]

I was really interested in the perceived wisdom of pocket holes in MDF . . . . my view is that if MDF can be avoided that's a good thing . . . but needs must on cost for many projects.
From what I've seen Peter Millard uses pretty much only MRMDF - and joints for the cabinets, shelves whatever are usually either Domino or a "mechanical" joint.

 

[TheTiddles]

I’d happily use MDF wherever it’s appropriate. It’s a perfect ground for veneer, extremely stable, easily painted, no grain to fill or tear and very cost effective. A great many super expensive masterpieces seen made now are MDF inside.

Our first set of wardrobes were B&Q nasty MDF and held together with loose biscuits and pocket screws. Build cost for two double wardrobes was about £45 (checkout person refused to charge me the correct price) and about £30 of that was the paint and screws, recycled hinges from my parents old kitchen and handles made from offcuts of steel tube and lag screws from a packing crate. We moved house with them twice, moved them inside the house twice and then passed them on to our neighbours when they needed something quick. Each time they were dismantled and reassembled, so what’s that... 6 assemblies, they still looked fine and worked as intended.

Aidan

 

[petermillard]

I was really interested in the perceived wisdom of pocket holes in MDF . . . . my view is that if MDF can be avoided that's a good thing . . . but needs must on cost for many projects.
From what I've seen Peter Millard uses pretty much only MRMDF - and joints for the cabinets, shelves whatever are usually either Domino or a "mechanical" joint.

Yes, MRMDF always; it’s a much better quality board for not much more money, and takes paint much better, and with less effort than regular MDF. I’m not a fan of pocket-holes generally - I think I’ve probably used 20 in 20 years - but they worked fine in MDF.

Personally I wouldn't go near ordinary grade plywood for something like this; The finishing would be horrible to do, And all the exposed edges would need lipping,

A ‘shelf/pidgeon hole’ piece doesn’t sound like there’ll be much unsupported span, so there shouldn’t be any issues with MDF sagging; if it’s wall-hung then I‘d usually fit a batten underneath it to take the brunt of the weight, or if it’d freestanding then I’d use a plinth for even support across the unit.

Back to pocket-holes; there’s an awful lot of filling involved before they can be painted, and it needs to be done with care if it isn’t to show through the paintwork; you’ll get a better finish, faster, just with regular screws or nails, and plenty of glue.

HTH P

 

[robgul]

It appears that the job has been done - see pic . . . . . not something I'd be proud of looking at the fit of the parts.

..... the bloke making it went rogue and altered my original design (having made his first pass at it the wrong size!) It will be painted (by the owner). I'm not happy with the vertical panels sitting on the floor - if the floor is mopped the moisture will run up the MDF . . . needs a plinth or lip of real wood, or some sort of pad/foot to get it off the tiles.

It's in a very small utility room and was designed to house the IKEA recycling bin set - the pallet wood veg rack (partial view) is on the top.

 

[Steve Maskery]

I was just about to post this. Looks like we are all too late. But, just for the record, and for anyone who stumbles across this in the future...

If done properly pocket screws are an excellent technique. Specify MRMDF, rather than the ordinary stuff. Design it so that all the screws are on hidden faces. That's how I did my wardrobe and I'd be disappointed if anyone described that as a cheap-looking job.
The load-bearing capability depends on the span, of course, so just make sure that all the shelves are short enough.

 

[robgul]

I was just about to post this. Looks like we are all too late. But, just for the record, and for anyone who stumbles across this in the future...

If done properly pocket screws are an excellent technique. Specify MRMDF, rather than the ordinary stuff. Design it so that all the screws are on hidden faces. That's how I did my wardrobe and I'd be disappointed if anyone described that as a cheap-looking job.
The load-bearing capability depends on the span, of course, so just make sure that all the shelves are short enough.

Agreed on pocket holes - I use them extensively . . . but seldom with MDF! -

 

[Cabinetman]

Well, let’s just say I hope it wasn’t a member.

 

[Farm Labourer]

" Well, let’s just say I hope it wasn’t a member."

Amazing who you bump into on here. I've had electronic dialogue with the chap who lives 2 doors and a mile away! He must have lived there for about 10 years and we've only very, very briefly met once - about 10 years ago.