However, Ikea sell extension units, but they are only intended to go on the full height units. This is frustrating as I could fit a four shelf unit into the new office quite easily. Not being an avid DIYer, I considered this and worked out that even I could get the extension units connected to the half height units.
All the needs to happen is for two holes to be drilled in the top of the bookcases. Measuring from the back of the side panels, a hole with a 5mm diameter and 10mm depth (wrap some insulating tape around the drill bit 10mm from the end and stop drilling when it meets the shelf) needs to be drilled with a centre at 241.5mm and at 8.5mm from the edges. Once this has been drilled on either side, Ikea's instructions can be followed again.
One other little refinement I made was flipping over the top shelf of the extension so that the four locking screws are inside the bookcase, rather than being on the top (as a four shelf unit is still low enough to see the top easily).
The extension units have these holes drilled in them so a further extension unit could easily be added to the top making a five shelf unit.
These measurements worked for me today with the units I bought recently. If Ikea modify their design at any point, I cannot guarantee they will work again: if you have found this post while looking to see if the extension units can be added to the 106cm bookcases, do check the measurements carefully on your units.
Update: May 2021
Having just had a loft conversion finished, I'm in the same Ikea/DIY position as I was nearly seven years ago to the day! I have just fitted two extension units which I have just bought to the 106cm Billy shelf units in exactly the same way, using exactly the same measurements.
Thanks Richard, I had a similar issue! The version I have (2015) you need to carefully drill the holes in the top at about 36mm in from the front of the bookcase with a 5mm bit. I drilled a very small pilot hole with a 2mm bit to get through the laminate first. Ironically, the extension comes with two holes in the top just in case you want to continue extending upwards...
ReplyDelete...and the height of the room meant we were able to add a second extension unit, so were glad of the additional holes! I assume it's because they think no-one could be that tall to see the empty holes on top of an extended six - now seven - shelf bookcase! I did vaguely wonder whether the holes would be there but just hidden under the veneer on the half-height shelves: sadly not. Anyway, glad to have helped and thanks for the pilot hole refinement.
DeleteThanks so much for writing on this. I kept googling on how to magically attach the extension unit to the top. In IKEA the extensions are right next to the 3 shelf units and nothing is on their website or in the catalogue. Being that I am only 5 feet tall, once the extension was added (by my loving husband) I can't see the holes on top. Again thank you!
ReplyDeleteTHANK YOU!!! I've been trying to figure this one out for a few days, and trust me, I've probably put together every IKEA thing out there! I'm actually kind of shocked that I found the exact answer to the exact problem I was having, that never happens. You would think IKEA would explain this as it's not at all clear. And, while we are on the Billy topic, why won't they make panel doors that are glass for the shorter unit?That is all....
ReplyDeleteThanks!
Thank you for advising I had to drill the holes into the unit. I thought I was going mad and and had missed some vital assembling stage. I never knew I had to drill a hole in IKEA ... always a first time.
ReplyDeleteStupid question, is the Billy 80cm bookcase exactly 800mm or is it slightly less? Asking for a wall cavity of mine.
ReplyDeleteI'll add my thanks to the rest. I just bought a half-height Billy and an extension. It's weird that they haven't changed this design issue yet.
ReplyDeleteI can only assume it's because for non-modified 106cm units they feel a hole in the top would be ugly. And I'm inclined to agree, in fairness! Nevertheless, glad the post was helpful.
DeleteI’m so glad I found your instructions !! Having checked my assembly numerous times to see if I missed something or wondering if I got a defective pack, I was ready to give up ! Even YouTube couldn’t help! Thanks so much for precise instructions . I’ll get my husband to it right away !
ReplyDeleteThanks for the post! We were wondering if we bought the wrong base. This explains it. Agree the holes would be ugly on the top of the shorter unit, but they could provide plugs... Either way, we drilled the holes and are happy with the result.
ReplyDeleteThis was very helpful. Thank you for sharing this informatoin.
ReplyDeleteMany thanks for the advice, Richard and David – but would you please say how you determined where the holes should be drilled. I assume it was so that they would align exactly with the holes in the extension unit. The reason I ask that if I used the measurements you specify, the drilled holes would not align exactly with those in the extension unit. Extensions unit and bookcase bought in UK in 2020.
ReplyDeleteI measured them very carefully! However, as I wrote on the original post in 2014:
Delete"These measurements worked for me today with the units I bought recently. If Ikea modify their design at any point, I cannot guarantee they will work again: if you have found this post while looking to see if the extension units can be added to the 106cm bookcases, do check the measurements carefully on your units."
If the design has changed recently and your find the measurements are now different, if you wanted to comment below, people might find it useful going forwards.
Thank you Richard. Yes, I had noted what you said in your original post. I was really seeking confirmation that it was necessary to get the drilled holes exactly aligned with the existing ones. I had wondered if the difference between my measurements and yours might be because the mechanisms of the fittings required the holes to be slightly misaligned. Which is the sort of misunderstanding of the obvious has led to so many mishaps in my experience of DIY. I doubt if my measurement skills are as good as yours, but I will have a go. I have bought some double-sided tape as a fall-back option if the drilling does not work. Thanks again.
DeleteHi Lycidas. Appreciate it if you could update whether the above mentioned measurement works for the latest Billy Bookcase. 🙏🏼
DeleteI just did this for mine, all stuff purchased in mid-September 2020.
ReplyDeleteThe only modifications I would say is that the holes need to ultimately be a little bit smaller than 5mm. I think they're 4.5.
I put the 4mm drill bit into the holes on the top of the extension, and it seems a bit small. I drilled the holes 5mm and the bolt that goes into them didn't quite grip as hard as it normally would, it seemed just a little bit loose.
With 5mm holes it still functions, though.
Also on mine I should have aimed the holes a tiny bit further back from the front of the cabinet. I measured it at 36mm but I think it's 36.5 or 37. Just be as close as possible on that one.
Thanks for the awesome tip, though!
Thanks for the update, Paul. I think it's essential that anyone trying this measures the items they have before doing any drilling, but hopefully leaving the original information will continue to let people know it's possible to make it work!
DeleteThe measuring and drilling for my extension unit has been completed at last, and successfully. For my units, purchased this year, the distance from the front to the centre of the holes needs to be 37mm. A hole drilled with a 5 mm bit turned out to be fine. To minimise measurement error, I bought a small set square with markings in mm from Amazon. I noted afterwards that 37 mm is the distance from the front to the centre of the holes on the top of the unit that have been put there by IKEA for those who want to add another extension unit. Presumably, if that were not the case, the front of the second additional unit would not not line up with the front of the first or with the bookcase. Thanks again to Richard and others for the advice.
ReplyDeleteThank You Richard and the other contributors for your observations, tips and general helpfulness in resolving the weird problem of the Billy bookcase extension!
ReplyDeleteThanks Richard.... your advice got me out of a bit of a pickle... we'll done you!
ReplyDeleteLikewise, thanks all. I was hesitant whether to go ahead with the short bookcase and extension until I read this. Thanks so much all.
ReplyDeleteWhat are the drill bit sizes you need. The dowel size on the side is not the same as the screw hole next to it. The round hole on the flat side next to the sides that is used for the putting on to the small shelf brackets is somewhat less than 3/8 inches but what is it. It has to be precise to give the shelf stability. The other holes further back on the flat side for holding the screw is larger than 3/8s.
ReplyDeleteThis is all for customizing the shelf, cutting down the width so it can fit. You then need to know every bit size to redo the holes. What are those drill bit sizes?
Thanks Richard, totally saved me from hours looking for pre-drilled holes in the 106 bookcase (I did for a bit) (also, is this clear from ikea site, that extensions are only pre-fab with full-length?). Anyway, going to try some drilling tomorrow! Thanks again.
ReplyDelete