Old and damaged floor joists are one of the main reasons for sagging or uneven floors. Unfortunately, in many homes, it can be quite problematic and costly to repair or replace floor joists. If you are lucky, your home may be an exception and the floor joists will be easily accessible from below, typically through the crawlspace. Even then there will be material and labor costs, however.
So, how much does it cost to replace floor joists, how long does the whole process take, and what are some of the other key considerations you shouldn’t forget?
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How much does it cost to replace floor joists?
By most estimates, the average cost of replacing floor joists is around $50 per square foot, including both the materials and the labor. That is, if the floor joists are easily accessible, however, and if nothing else needs to be done. Additionally, the problem obviously never spans just a single square foot – at best, you’ll only need to replace a single floor joist but even that is multiple square feet.
So, depending on the severity of the problem and the layout of your home, the overall cost can range anywhere between a few hundred dollars and north of $20,000 if you’re really unlucky. More often than not, however, the cost will be in the 4-digit range – over $1,000 but less than $10,000.
What factors into the overall price?
The two factors that are always current are materials and labor. Even if you’re doing the repair or replacement yourself, your labor is still something to keep track of – “time is money” as the old adage goes.
Also, note that you may need to purchase a lot more materials if you’re trying to fix the problem yourself as you may not have all the tools a professional contractor does.
1. Materials
The joist replacements or repair costs usually start with the purchase of new joist beams. These can cost anywhere between $200 and $500 per beam, depending on the size, type of wood, and where you’re buying them from.
This means a cost of somewhere between $10 and $67 per square foot for the joist beam alone. Obviously, this doesn’t include all the minor additional costs for nails and other such materials.
These costs can be lowered if the structural repairs don’t actually necessitate a new joist but just sistering the old one. If the issue is indeed mild enough that just sistering the joist is enough, then you are likely in luck as you won’t have to purchase that many materials.
Still, even then you’re going to need things such as adhesive, a nail gun, and a hydraulic jack to level the structure. You may be able to borrow some of these tools from a friend if you don’t have them yourself. However, if you have to purchase such things in addition to the sistering joist or the new replacement joist beam, then you’re likely better off just calling a professional.
2. Labor
The labor costs are a big part of the overall cost estimate. Repairing hardwood floor joists usually costs somewhere between $65 and $100 per hour. You may be able to get better quotes in certain states and areas but be wary of overly low prices as they may denote poor work quality.
Assuming a repair floors cost of ~$100 per hour and a work time of a dozen or so hours, you can see how the labor alone will push your budget into the 4 digits. This becomes especially likely if the floor joists aren’t accessible from underneath the flooring itself needs to be partly or fully taken apart. Naturally, this will also lead to a series of other costs we’ll detail below.
3. Floor replacement or repair
Whether your floor is made of ceramic tile, laminate, carpeting, hardwood planks, plywood, vinyl, or anything else, having to take it apart to get to the damaged beam underneath isn’t going to be free or likely even cheap.
Some types of flooring can be reinstalled back after they’ve been removed to access the joists but other flooring types are not as reusable. Even in the case of the former, it’s usually better to just put new flooring down once you’re done with the joist beams.
This, in turn, means that you want to make sure everything with the joists is as good as it can be as you wouldn’t want to have to remove your new flooring in a couple of years too.
Cases like these are the ones that usually get extra costly as they basically end up being a complete remaking of the flooring and most things underneath it. The good news is that, if everything is done well, there shouldn’t be any more need for floor repairs in the coming decades.
As for the exact cost of the flooring – that depends on the square footage and the type of flooring you’d go for. Hardwood planks, for example, usually range somewhere between $6 and $18 per square foot for both materials and labor. This means that just the flooring for a single room of about 200 square feet can cost anywhere between $1,200 and $3,600.
4. Subflooring replacement or repair
Underneath the flooring and just above the floor joists is an extra layer called subflooring, usually made of plywood. The average cost to repair subfloor made of plywood is anywhere between $2 and $10 per square foot or $500 to $700 for the average room.
If the subfloor isn’t healthy enough to just be repaired and it needs to be replaced entirely, the cost homeowners can expect here is in the thousands – usually between $1,000 and $3,000 per room for a plywood subfloor.
In addition to the subfloor repair cost you’ll usually have to deal with your floor’s underlayment too. Not all floors have that and there is a difference between a subfloor and underlayment. In short, the underlayment is an optional middle layer between the subfloor and the flooring – it’s traditionally meant to help with squeaky floors, to offer extra heating insulation, or to help level the floor.
Either way, if you’re having to take the flooring and subflooring apart to get to the joist beams, you’ll probably need to go through the underlayment too which will cost extra.
5. Inspection
Even if you’re adamant about doing all of the above yourself, or even if the problem is actually much more manageable because the floor joists are accessible from below, you’d still do well to call a professional inspection before you do anything.
Such an inspection will cost between $300 and $500 but it’s essential for properly assessing the structural damage, water damage, mold, termites, moisture, leakage from pipes, and whatever other side issues might have arisen from the floor joist problems or might have caused them in the first place.
As steep as ~$500 can feel at first, it’s very common that such a professional inspection will save you a lot more down the line.
How long does replacing floor joists take?
A floor joist replacement professional will usually be able to take care of the whole floor joist repair or the installation of a replacement joist in about a day – sometimes for as little as a few hours, other times for up to 24 hours (so, 3 work days).
If you want to try doing it on your own, however, you can expect the whole thing to take quite a bit longer as even the more skillful and experienced DIY enthusiasts are usually not as expedient as a professional contractor.
Can you repair or replace your floor joists yourself and should you try?
Technically, you can, especially if you’re experienced in DIY floor repair. Some floor joist repairs can be easy too – if there is only one damaged joist, if the rotting is limited, and if the whole thing is easily accessible and you won’t need to take the flooring apart.
A professional contractor will be able to give you an accurate price quote, will assess the damage, and will outline any additional risks to your home’s foundation, basement, crawl space, floor, plumbing, and so on. This isn’t to say that you shouldn’t have a look yourself first, of course, especially if you know what you’re looking for.
But the risks and problems that have come from people attempting a DIY fix when the problem was major enough that it warranted the hire of professional help are incalculable.
In conclusion
All in all, the average floor joist repair cost can be difficult to predict. The typical range is usually in the 4 digits but it can depend on a lot of factors, including even your zip code. Calling a general contractor early is also a good idea most of the time unless you’ve done this sort of thing before.
It’s also important to note that floor joists should be fixed not just as soon as possible but as thoroughly as possible too – otherwise, these sorts of problems tend to reappear quickly and significantly worse than before.