Any imperfections that are not properly dealt with prior to laying your laminate floor will not be able to be corrected until the laminate flooring has been lifted, and will likely then need to be replaced.
I will discuss the best ways to correct uneven subflooring below; taking into consideration the various materials that your subfloor is likely to be built from including wooden floorboards, chipboard, and of course concrete.
How to Fix Uneven Wooden Floorboards
Floorboards in my experience are prone to warping and are often found in older properties. Because hardwood flooring is seldom replaced due to the expense, uneven surfaces can often be found. Assessing your floor as though expense and time is not an issue (even though we all know that they are) is often the best way to determine whether the flooring will require some corrective work.
Secure Your Floorboards
The first step in assessing your floor should be to ensure that all your floorboards are secure. Walk around the room and listen carefully for squeaking as well as underfoot movement. If you come across movement or noisy floorboards attempt to fix these by screwing them in (don’t nail them).
If your flooring is only uneven because of a single plank, or because a small number of planks have risen above that of the rest of the flooring consider replacing these rather than declaring your whole floor uneven. In certain cases, an electric sander may help you correct some minor flaws.
Deciding How Best To Fix Your Subfloor
After securing your floorboards, assess how uneven your subfloor surface still is. If the floor is only slightly uneven you will be looking to cover your subfloor with thin hardwood (3mm or 1/8 inch), alternatively, for subfloors that require a high level of correction, we will be looking to cover the floorboards with ½” or preferably ⅝ plywood.
If your floor slants from one side of the room to another, you will have to call a professional, as this will likely be a structural problem.
Assuming the problem can be fixed either using hardwood or plywood, refer to your room’s measurements (as discussed in our article How To Measure A Room For Laminate Flooring) and order the hardwood or plywood that you will require. See my tips below on ordering the wood sheets.
Tips on ordering hardwood or plywood for your new subfloor
When ordering either hardwood or plywood with the intention of leveling out your subfloor the size of the wood (as well as the thickness) should be considered. As a general rule of thumb the larger the sheets of wood (whether hardwood or plywood) the better. The larger the sheets of wood used the fewer joints will be required, in addition, the more floorboards a sheet covers the more gradual the ironing out of the uneven floor will be.
Of course, a consideration when ordering these sheets of wood will be transportation, as larger sheets will be more difficult to transport.
When shopping for sheets of hardwood or plywood we strongly suggest looking at the larger DIY chains as they often carry a lot of stock and will either deliver or make the collection as simple a process as possible.
Other Tools and Materials Required
In addition to the wood itself, it is a good idea to ensure you have all the tools that will be required to cut and attach these boards to your subfloor. Below is a short list of tools that you will definitely need to either buy, borrow, or steal (not the last one) to install your new subfloor in preparation for laying your new laminate flooring. You may already own many of these tools – if so great!
Remember that although this may seem like a lot of work, when you finally come to lay your laminate flooring it will look way better than if you had just laid it on an uneven surface, and who knows may even increase the value of your home.
Many of the tools below will also be used when it comes to laying your laminate flooring, buy once, and use it for a lifetime. The tools we have linked to are our personal recommendations but feel free to buy alternatives if you believe they will better suit your needs.
Tools List – (Amazon Links)
Plywood or Hardwood – Order the correct amount of hardwood or plywood based on the size of your room taking into account possible wastage.
Tape Measure – A simple tape measure to help you plan and cut your plywood or hardwood to the correct sizes.
Straight Edge – A straight edge to plan your cuts before you make them.
Electric Drill / Driver (If using plywood)- If you are laying a plywood floor we strongly advise that you screw the plywood into your wood subfloor. Some recommend nails, but we believe screws work much better.
Stapler (If using hardwood)- While it is quite possible to simply use nails a staple gun will help you get the job done much quicker. We have recommended a reasonably priced staple gun to use that will get the project done to the right standard.
Staples (If using hardwood)- If you buy a staple gun, you’ll need staples.
Stanley Knife (If using hardwood) – Hardwood can be cut by simply using a sharp stanley knife, we will discuss how this is done later on in the article.
Screws (If using plywood)- Self-countersinking screws to hold your plywood in place. These screws are easy to use and will make sure your plywood is held firmly to the floorboards.
Circular Saw (If using plywood)- A circular saw will help you cut the long straight edges on the plywood accurately. You can of course opt to use a hand saw if you prefer,
Jigsaw (If using plywood)- A Jigsaw will be required for making those all important curved and intricate cuts. Use the jigsaw to cut the intricate shapes created using the profile gauge. A jigsaw can also be used for straight cuts (with a thicker blade), though we would advise using a circular saw instead.
Profile Gauge – A profile gauge will help you make your intricate cuts by profiling curves using steel needles.
Work Bench – Using a workbench is much easier than making all your cuts on the floor. A good workbench should be big enough to easily rest your plywood or hardwood wood planks on to make your cuts (so consider the size of your boards before purchasing)
Knee Pads – a good set of knee pads will make your job more bearable. You will be kneeling on the floor for extended periods of time so investing in some good knee pads will help you get your job done a lot faster, safer, and with less pain.
Preparing Your Plywood or Hardwood
Once you have your hardwood or plywood, other materials, and tools you will be wanting to get started. The first step will be ensuring that your floor is free from excess dirt, and dust that may get in the way.
Lay as many sheets on the floor (unfixed) and walk over the top of them to give you a general idea of how even the floor will be once laid – assuming that this test provides you with a positivity that the boards will iron out the unevenness of the floor you are ready to proceed.
Acclimatizing your wood
Firstly, you will be wanting to acclimatize your wood to the room. This is done to ensure that they don’t expand or shrink once you have laid them, otherwise, you could end up with gaps, or in the worst-case scenario, your boards could warp.
Hardwood can be acclimatized relatively quickly, but the process also requires a little more work than simply just putting them in the room where they are going to be laid.
Unpackage the hardwood boards, and scrub water using a scrubbing brush into the rough side of the hardwood boards. The sheets should then be laid in the room in which they will be fitted for approximately 24 hours before use.
When stalking the sheets, the rough side (wet side) should be facing each other so as not to get the smooth side of the sheets wet.
After 24 hours your sheets will be ready to be laid.
This process is unfortunately not a short one, as your boards should be left (within packaging is fine) in the room you intend to use them in for a period of about 2 weeks before laying them.
It is important during this time to try and keep the room as it is likely to be after the sheets are laid. Make sure the temperature remains consistent with the normal temperature deviations (night and day) that will likely occur once the boards have been fitted into place.
Removing Skirting Boards
Whether you plan to remove skirting boards or not prior to laying your laminate flooring is a personal preference, if you don’t you will need to add a beading around the room (here is an article I have written regarding this decision).
Removing the skirting and putting it back in place once the laminate has been fitted is by far the most preferred method as it looks better, and will provide a far superior finish than using beading.
It is also worth remembering that because you have decided to either use hardwood or plywood to create a new subfloor, the floor will be raised – so it makes sense that the skirting boards should be raised too.
I would suggest removing your skirting boards, here is an article I have written on removing skirting boards without causing damage.
Laying a Hardwood Subfloor
If you are fixing your subfloor with hardwood read on, if using Plywood please skip to the next paragraph.
We will be fixing the Hardwood using either a heavy-duty stapler or alternatively ring shank nails. Both should be perfectly adequate to get the job done.
The hardboard should be laid smooth side up and should be placed so as to cover as many floorboards as possible. (see image below)
We will not be attempting to fix these boards to the joists, instead, each board will be fixed to the floorboards at 15 cm intervals.
Once your first piece of Hardwood has been laid (corner of the room is fine) and attached, simply butt the second board up tightly against the first sheet and attach. Try and keep the boards as neatly aligned as possible.
Work your way across the room staggering the joints between subsequent rows until you only require to cut some hardwood for the final gap.
To easily cut hardboard use a steel ruler and retractable knife (Stanley knife) to score the hardboard at the point you wish to cut. Turn the board overlaying the steel ruler over the scored line and bend the board, you can now simply use the retractable knife to make your final cut.
Laying a Plywood Subfloor
Fitting a plywood subfloor is arguably the best way to ensure your laminate flooring (or virtually any other flooring you wish to lay) is fitted to the very highest standard. The main issue with plywood is the time it takes to acclimatize, and the extra time required to fit the plywood correctly.
You should have already ensured that your floorboards are secure and that there are no screws or nails protruding or likely to get in the way when fitting the plywood. Also, remove your skirting boards.
Lay your first piece of plywood tightly in the corner of the room. Your plywood should cover as many floorboards as possible (see image below).
We will be fixing the plywood to the underlying floorboards and not to the joists, to do this we will secure the piece with screws every 15 cm along the edges of the wood. We will then secure at 15 cm across the center of the board as well. These screws should fix the plywood to the floorboards but should not go through them.
Tightly fit the second piece of ply, keeping the boards as neatly aligned as possible, fixing them as you continue along the room.
Straight cuts can be made using a hand held saw, though you will likely need a profile gauge and jigsaw to make cuts around pipes and other non-straight edges.
Once you have covered the whole floor you will be ready to fit your laminate, though you may be required to trim your doors due to the height difference that the plywood layer may have made.
How to Fix an Uneven Concrete Floor
Concrete floors leveling issues can be fixed using a self-leveling compound mix (Amazon link) that basically uses natural gravity to fix your uneven concrete floor.
Start by ensuring your floor is clean and that any debris has been swept up so as to avoid anything getting caught up in the mixture (once poured).
You will need to prime the concrete floor (the perfect primer to work with our recommended self-leveling mix). Whichever self-leveling compound mixture you have chosen will provide further advice on what should be used and how this should be done. Stick to the manufacturers’ guidelines.
Mix the compound (consider using a mixing paddle) as per the instructions, and pour the compound onto the floor. The compound will settle at its own level. Keep mixing compound and pouring in various areas until your floor has been covered.
It is a good idea to use a flooring trowel (Amazon link) to smooth out any lumpy areas. Try to work as quickly as possible as the flooring compound will set quickly.
Tools List – (Amazon Links)
Self-leveling compound mix – Self-Leveling Underlayment helps level floors prior to the installation of ceramic tile, natural stone, resilient flooring, carpet, wood, and other floor coverings. This quick-setting underlayment can be applied to 1.5 in. (3.8 cm) thick in one pour and seeks its own level in minutes.
Primer – This primer and sealer seals porous surfaces and improves the bond of underlayments.
Flooring Trowel – Basic flooring trowel to help you smooth out edges.
Mixing Paddle – Mixing paddle that will help you mix the self-leveling compound mix to the right consistency.
Bucket – Simply a bucket to mix your mixture into.
When your Subfloor is Level
Once you have ensured that your subfloor is as level as is going to be possible you will be ready to move forward with the actual job of fitting your laminate flooring.
Fixing a subfloor leveling issue can seriously set you back in terms of time, but the extra work will definitely pay off and your completed floor will look as though a professional has laid it.
Always address leveling issues before attempting to lay any type of flooring. The extra dedication will pay dividends. There is no worse feeling than a daily reminder of a DIY job that you know you could have done better – take my word for it.