Plasterboard sizes: A pro guide on what to use and when

Pile of plasterboard sheets outside
(Image credit: Getty Images)

Deciding on what plasterboard sizes you need for your next DIY project is key to getting the best finish. What you need will depend on the specific project you are working on; for instance, are you building a standard partition wall to divide a room,  installing a new ceiling or covering up brick and block work?

When plasterboarding a ceiling you are likely to need a different size plasterboard than if you're fitting a stud wall. Not every scenario is the same and while there are common choices, even then the decision is not always straightforward.

Here we take a look at the common options and how to choose the right plasterboard size for a project. 

What are the common plasterboard sizes?

There are two common sizes that are used across most plasterboard projects — 9.5mm thickness and 12.5mm thickness.

The benefit of 9.5mm is that it is thinner than 12.5mm plasterboard, which makes it lighter and a more common choice for ceilings. If you are looking for more insulation and better soundproofing you can use 12.5mm on ceilings, assuming you have the correct fixings.

Plasterboard at 12.5mm thickness is the most commonly used plasterboard sizes and is a popular choice for dot and dab plasterboarding and walls in general. If looking for more heat and sound insulation it is possible to find 15mm plasterboard, but this is not as easy to find. Typically if selecting moisture board instead of plasterboard, for moisture-rich areas, this is usually 12.5mm rather than 9.5mm in thickness.

How do you choose what thickness plasterboard to use? 

Typically this is a choice between 9.5 and 12.5mm plasterboard, but not always. Gary Blackburn, Plaster Support Manager at Saint Gobain reveals what you should do first, “The first choice is based on the space between the joists”.

The space between joists is typically 400mm or 600mm with 400mm being the more popular. It's worth noting that if you want to know how to build a stud wall these are the common measurements for stud spacing. If using 400mm spaced studs 9.5mm plasterboard is the common choice. If working with 600mm spaced studs, 12.5mm plasterboard is the common option.

Blackburn adds that, ‘additional performance’ is a consideration as well. By this he means fire resistance and sound insulation. So if you need improved sound isolation and fire resistance, a 15mm board is better than 12.5mm plasterboard. 

Which plasterboard widths are typically used?

There are a lot of different sized boards available, but 900 and 1200mm are common widths, with 1200mm width plasterboard neatly fitting 400mm and 600mm studs and joists.

There is much more variety in length with sizes typically ranging from 1800mm to 3000mm. 2400mm is a popular length as this is equivalent to around 8 foot, which is a common ceiling height in UK homes.  

What is the best way to cut plasterboard? 

There are several options when it comes to cutting plasterboard. A sharp Stanley knife and a long straight edge such as the Silverline SL22 Spirit Level found on Amazon are a typical choice. You make a cut with the knife and then bend the board to snap to size.

For more than a single straight edge or curves a jigsaw is a good choice. Finally, to cut holes in plasterboard you need to invest in a jab saw like this Irwin Jab Saw for Plasterboard found on Amazon.  

Is it better to nail or screw plasterboard? 

Plasterboard screws are the preferred choice for those in the trade. When screwing into plasterboard use bugle head screws as they are countersunk and sit flush without breaking the paper or plaster. Also consider the length of the screw. If using 9.5mm plasterboard use a 32mm screw, if using 12.5mm plasterboard use a 38mm screw. 

DIYers who are not so confident with plasterboard should use a dimpler like the one found in this Laser Drywall Bit Set on Amazon. This has a collar that helps stop the drill bit going into the plasterboard. 

Nails can be used but there is much more chance of missing the board and breaking the paper and crushing the plaster behind the paper.

Can you paint straight onto plasterboard? 

The easy answer is yes, you can paint straight onto plasterboard, but it will depend on the location of the plasterboard. Standard plasterboard is not waterproof, which means it is not suitable for areas that are in contact with water or moisture on a regular basis i.e. kitchens and bathrooms.

However, if the plasterboard is located in a room such as a bedroom or lounge you can paint the plasterboard without having to plaster. However, you will need to use a suitable filler to fill the joins to get a smooth finish before you paint.  

Steve Jenkins

Steve is Homebuilding & Renovating's DIY content editor, and has been a writer and editor for two decades. He is an avid DIYer with over 20 years of experience in transforming and renovating homes. He specialises in painting and decorating, but has strong all-round building skills, having previously worked in the industry for 10 years.