If you're fixing anything to anything, you need to know what you're fixing into. Here's the information to help find out.
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This is one of four posts:
One on figuring out how your wall is built (this one)
One on checking what's hidden in your wall before you drill through it
Walls are likely to be your biggest problem in understanding exactly what you're drilling into and fixing to. Get it wrong and you can trash your tools and the wall.
For exposed brick or block (like in a garage) it’s fairly easy, select your drill bit on the choosing a drill bit page and away you go.
But, if you have plaster, plasterboard or some other board finish, or a wall that isn't brick or block at all there are some things you need to think about. If you‘re fixing or hanging something heavy (shelves, TV bracket) you need to think about what will carry the weight. If there's a solid wall behind, use that. If there isn't, you will need to consider how you'll do it or even if you should do it at all.
Let me explain that:
A main supporting wall will generally be brick or block (I'll get to things like timber frame houses in a minute). So the outer walls of the house, the wall between you and the neighbour (if your houses are joined) and any walls that support the floors above will likely be brick or block. To make the brick or block look nicer on the inside, older houses will have a base plaster directly onto the wall and then a finish plaster coat to smooth it off. More recently for the same type of brick or block wall you may have sheets of plasterboard "glued" to the wall (dot and dab) or screwed to thin wood strips that are in turn screwed to the wall. Something like this:
Simply put, if it’s heavy or if you want it fixed well, your fixing needs to go through into the main wall.
A non-supporting or partition wall can be a whole host of other things.
Can be block or brick for older houses, often a thinner block than the supporting walls.
Even older houses might have lath and plaster which is a timber frame covered with lots of thin strip of wood nailed fairly close together and then plastered over the top.
Could be a wooden frame with plasterboard attached.
Might be 3 or 4 sheets of plasterboard glued together.
If you're really unlucky it could be Strawboard or Stramit which like it's name suggests is straw compressed and stuck together to make a sheet about 50mm thick (very good thermally but a nightmare for many other reasons)
It could even be boards like ply or OSB.
I'm sure there's many other possibilities but I've not encountered them myself.
So something like below:
If you're panicking now at the thought "oh my word, I don't know which of these my walls are" DON'T! We'll come to that shortly but you needed to know what the possibilities are!!!
Timber framed houses and other specialist builds. Timber framed houses don't have supporting brick or block walls but they do have a framework of timber. In a way you can think of them like the partition walls mentioned above. I've no experience of them but I will say that you need to take advice on putting holes in the outer walls particularly because you may compromise the integrity of the structure. There are other specialist build methods used particularly in self build schemes but I'm guessing if you built it yourself then you've got an idea of how it all works already.
The list above is by no means exhaustive but it covers a lot of the basics. If you’ve got something different, let me know and I’ll add it in.
Lets get to business then
First, think about the location of the wall
Outside wall? Probably blockwork faced with plaster or in a newer home, plasterboard.
Interior wall? Read on.
Can you tell if it is directly below an upstairs wall? Or directly below a downstairs one? Reasonable chance it’s a supporting wall and therefore brick or block.
If it‘s fairly close to the centre line of the house it may well be supporting and brick or block.
How about its thickness? To try and figure the thickness find a doorway and try to gauge how thick the wall is. If it’s less then about 100mm there’s a good chance it won’t be brick or block. Now, irritate your neighbours and knock on the wall. You’re trying to find out if it’s hollow or if it has some hollow spots. If it all sounds hollow nearly all over there’s a good chance it’s stud partition (plasterboard on a timber frame) which would normally be internal non load bearing. If it’s an outside wall or it sounds hollow only in places but also sounding quite solid in places then more likely plasterboard fixed with dot and dab.
Now some actual testing
STOOOOOPPPPPP!!! Just before you go poking holes in your wall, do all your cable and pipe checking first!! Check this post on what's hidden in your wall!
Turn off the power and take out a lightswitch or socket on the wall in question. Can you see what’s behind it? Make sure the power is off before you put your fingers anywhere near it.
If you can’t tell by some other means, you next need to make a small hole in the wall. Ideally with something like a blunt masonry drill.
A thin blade insulated screwdriver is good so if you do hit a cable you don't get a shock. If you have an old insulated screwdriver that's no good for screws, keep it specifically for this purpose
In a place where the hole isn’t going to be seen (ideally where you’re planning to put the hole for your fixing), use your blunt screwdriver or a thin blunt drill to make a hole.
It's very difficult to describe what it feels like if you go through plaster into a cable. There is a change in the effort needed to push on the screwdriver as it hits the plastic sheathing but the sheath is only thin so you don't have much opportunity to "experiment". If you are in any doubt at all, turn off the power and make the hole a bit bigger so you can see what's there.
A pipe on the other hand give a dead stop and the "grinding" feeling of going through the plaster changes to one of just turning but no further movement. Again, stop straight away and enlarge the hole to check what's there. If you're using a drill, be careful because it won't take much effort even with a blunt masonry bit to go through a copper pipe.
If you feel the screwdriver go “through” the wall without a great deal of effort and with a couple of twists and suddenly you have no resistance you’ve probably gone through plasterboard on something like a timber frame.
If it goes through the board and then hits something again after about 20mm you’ve probably got dot and dab plasterboard on a brick or block wall or maybe sheets of plasterboard bonded together (check the wall thickness at a doorway).
If you don’t get the “it’s gone right through” feeling and you hit something solid, maybe it’s plaster on brick. If you can still work it deeper but it’s hard work, possibly plaster on block.
If you’ve already found the wall isn’t all that thick (less than 100mm) first things first, make sure you don’t end up going right through it! If it’s plasterboard you’ll see plaster dust (logical really and something I should have drawn attention to earlier).
If it feels like you’ve gone through a tough layer of something like cardboard and then gone into something soft ish, if your house is say 40ish years old you may have found something like strawboard. If that’s really what you’ve found then I’m really sorry but you may have to take the 72” TV back to the shop. Strawboard barely has the ability to hold itself up let alone anything heavy. I welcome any comment from anyone that’s found a way to safely fasten to it. Many years ago there were special fixings available but they’ve long since gone. The only way I ever found was to put a board on each side of the wall and screw or bolt right through.
A note about windows and doorways in supporting walls.
If you have an opening in an external or supporting wall there will be something above the hole to hold up the wall above. Internally it could be concrete, outside it will likely be metal. Metal lintels as the beams are called are made so that you can’t see a big chunk of it on the outside. Inside it doesn’t matter because it will be covered in plaster. Or at least it doesn’t matter until you try to drill holes in them. More about that in the choosing a drill bit post.
If it's an external wall you will likely be able to see the edge of the steel lintel above the window or door like below. If you look directly above the window frame you can see a metal strip, that is the edge of a lintel. On the inside that will be a steel beam anything up to 150mm - 200mm high spanning across the window opening and going into the wall either side by 200mm or so
You can see on the 3 photos above I've marked the approximate position of the lintel on the inside so whenever you're drilling in that area you can expect to either be drilling into a steel box or a concrete beam just behind or above the plaster or plasterboard
Ceilings
Slightly less of a drama, ceilings for a long time have been plasterboard nailed or screwed up into the wooden joists above. Before that they were lath and plaster in a similar manner. Same cautionary note as always about cables and pipes.
Essentially you’ll either be fastening to the plasterboard (nothing too heavy then) or into the wooden joists. So pretty much all you need to figure is where the joists are.
If you can get under the floor (or into the loft) above your ceiling you can see the direction of the joists and the spacing s between them. ‘You might be able (if you have a strong magnet or metal sensing cable finder) to find the nail or screw lines where the ceiling is secured to the joists. If not you’ll need to do a bit of trial and error to locate the joists if you need them. Again if you can get into the void above you can push a bradawl through right next to the joist so you can see it below.
If you’re dealing with a ceiling in a flat there’s a chance you might find plaster on concrete or something horrible like that. Just means it’ll be harder work.
Floors
Leaving aside “coverings” from vinyl through to ceramic, your most likely materials will be traditional floorboards, chipboard flooring and concrete screed.
AGAIN, watch out for cables and pipes because they are often directly under the boards.
If you have any form of underfloor heating, take specialist advice before you do anything.
So now you have an idea of how to figure out what your wall or whatever is made of you can head off to look at the different types of drill bit and fixing you can use.
All the above is based on average UK homes. Elsewhere in the world different building materials are used in different ways to different rules but the basics remain broadly the same in that even if your fixings say on the packet they can support your 100kg fish tank, if the wall isn’t strong enough your tank will prove how effective gravity really is.
Be safe.
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