Fixings for heavy shelf in plasterboard

anotherbaldrick

The metal screw in type fixings do not work, the plastic equivalent ones do work, they are available in our area from Travis Perkins.

blogger57

The key to fixing in plasterboard is to understand that it is quite a weak material and doesn't take a lot of load. So to get a fixing to carry a heavier load then consider a few options:

• Fix into the timber studs that go vertically or horizontally behind the wall using a woodscrew
• If the cavity behind the plasterboard is small and there is an outside brick wall the other side of the cavity, then you may be able to use a longer version of a conventional Rawlpug plastic plug and screw. Theses are called frame fixings and can come in sizes from 120mm to 240mm. Clearly this method is no use if the wall is an internal partition wall.
• Use a fixing designed for plasterboard. By using more fixings i.e. say 4 rather than 3 you can reduce the load on any one fixing and spread the load over more material.

If you have to go for a specific plasterboard fixing, then the ones that spread the load over a bigger area of plasterboard will perform better. In order of weight holding I would go for:

• Interset metal fixing - this is designed with wings which collapse to spread the load. It uses a separate machine screw so you can remove the screw and the fixing stays in place. (see Rawlplug website for one example - I think they are also known as Molly fixings or brolly fixings). They do need a special tool which is quite cheap - you can also set them by just tightening the machine screw but you have to be a little careful as sometimes the fixing then rotates in the hole as you do it.
• Spring toggle metal fixing. Metal wings on a spring are pushed through the hole and they then expand inside the cavity to spread the load. They also use a machine screw but the downside is the hole to push the wings through needs to be much bigger and if you take the machine screw out then the toggle bit falls down the cavity! That's fine if you never want to remove the machine screw. You also need a deeper cavity for them to work.
• Plastic plasterboard fixings. These look a bit like normal Rawlplug plastic plugs and when the woodscrew is tightened the plastic end just folds up behind the plasterboard, forming what looks like a knot. Some of the designs have a split down the middle but they all do basically the same thing.
• The metal screw-in fixing shown in a photo in this forum is great to install for speed but is the worst for weight bearing. Why? Well it cuts the plasterboard up as it is screwed in, weakening an already weak material. Then it doesn't spread the load as there is no expansion at all. For weight they are not as good as the plastic plasterboard fixing which at least requires a smaller hole to be made.

As a summary, just think about how best to spread the load because generally in plasterboard it will be the material that fails rather than the fixing.

Hope this helps.

diyaction

Thanks so much for all for your help! If I had time I might try out the DrylinePro things but I need to sort this today so off to Screwfix once the sleet stops and I'll get some interset metal fittings or 'hollow wall anchors' as Screwfix call em.

Just a friendly note for anyone considering a visit to B&Q - Screwfix are often about 1/10th the price for items like this!

My only question now is what size fittings to get ... the cavity behind the drywall seems to be about 60mm - any thoughts?

www. screwfix.com/c/screws-nails-fixings/hollow-wall-anchors/cat840108