As builders seek to diversify their offerings more and more, they learn that renovation work is just a different animal.

It’s one thing to spruce up a pool that your company built, because then you know what you’re dealing with. But that’s not usually the situation. Instead, renovators are confronted with the unknown: They don’t know how the structure was built or finished, what kinds of soil conditions they may face, or how the pool has been cared for over the years.

One of the biggest challenges is learning to detect problems that could complicate the renovation itself, or just make life more difficult for the homeowners in the future. As a professional who was on the forefront of expanding the plastering business model to include full-scale renovations, Scott McKenna knows this well and has become an old hand at seeing red flags.

Here, McKenna shares some of the top indicators that an unexpected issue may need to be addressed.

• Poor or missing joints: This continues to be the most commonly found mistake, especially in older existing pools, McKenna says. Not only is it one of the most preventable mistakes, but it’s the root of many problems, including movement of the shell and detached tiles.

“We see that on so many pools,” McKenna says.

Coping joints may not be properly isolating the deck from the pool shell, so the deck touches the bond beam. Or a 3 ½-inch-thick deck may be bordered by a joint that only dips into the ground 3 inches, thus not forming a complete barrier between coping and flatwork. As the deck expands and contracts, it can move the pool or spa shell, causing coping and waterline tile to pop.

Additionally, builders often fail to place joints around skimmers. “So all the movement that’s gone on that deck is putting pressure on the skimmer,” McKenna says.

This can result in warping or cracking of the skimmer.

When they assess a job, McKenna’s crews survey the deck and skimmer joints to see if they should be redone — or added anew, in the case of missing skimmer joints — to prevent problems down the road. “This is something that potentially is going to be a problem, and if we’re here doing work, we should address this,” he says.

• Deck heaving or settling: Heaving likely indicates ground issues – perhaps expansive soils. This also can create something of an optical illusion for homeowners, who may try to convince the renovator that, no, the deck hasn’t risen, but rather the pool has settled.

Expansive soil can have long-term effects on renovated decks or shells. Contractors who suspect this is an issue should determine the soil conditions and consider whether any new deck or shell work will need extra reinforcement. Consultation with a geotechnical engineer may be appropriate.

If ground movement is expected in the future, extra maintenance may be required on the joint between the coping and deck — it may need to be redone every 3- to 5 years to ensure it continues to provide a complete barrier.

“In the case of expansive soil, even if you do the joint properly, and you pour the deck back, compact and bring in sand, it’s still a potential problem,” McKenna says. “You don’t want to allow moisture to go under the deck, because that’s where the problems happen.”

If the deck is settling, it could indicate improper compaction. This is most commonly found near the shallow end, which is where excavators usually dig their ramps to provide access down into the pool cavity. After the back hoe leaves, some contractors do not properly fill and compact that area before placing the deck, McKenna says.

• Cracks or out-of-level pool: These signs can be obvious (in the case of cracks) or not-so-obvious (out of level), but indicate possible settling or other structural problems.

In the case of cracking, dye tests should be performed to determine if they’re structural or cosmetic.

If the pool or spa is out of level, renovators face something of a quandary: To re-level or leave it alone? The latter option may seem like ignoring the problem, plus, it may be plain to see that the waterline doesn’t sit correctly against the tile patterns or joints. But fixing the problem involves removing the coping and tile, floating the low side of the bond beam so the coping is level on all sides, then replacing the tile and coping. But then the coping no longer lines up with the deck, unless at least part of the deck is redone.

“We have that conversation upfront instead of after it’s done, when they say, ‘How come my pool’s out of level?’ McKenna says.

• Old junction boxes: If a new light is part of the equation, make sure that existing junction boxes meet code. If they’re old and in the deck, then many local laws will dictate that they be brought up to code.

“You have to saw cut the deck and run it out and get it above water level,” McKenna says. “That’s a conversation you should have before you sign a contract, rather than selling them the light, then saying, ‘Oh, by the way, it’s going to cost you another $600 to get your j-box replaced.’”

• Safety code violations: It’s true that the law may not require a renovator to alter pools and spas to meet the latest safety codes, especially if a permit is not required. But many professionals insist. That includes McKenna — at least for certain aspects.

“If it’s a single suction main drain, we just won’t do it without splitting the drain,” he says. This applies even for work that doesn’t require a permit.

• Underwater windows: This product category has always been a tough one, and it represents one of the most expensive fixes McKenna’s company has had to do. When finding one on a renovation job, professionals should tread lightly.

“There just is kind of an inexact science to these underwater windows, especially the older ones,” McKenna says. “They’ve been there a long time, they might be a little warped.”

In one instance, he replaced the gaskets, and the window continued to leak. “We owned it,” he says. “It was our deal, so we spent the better part of six or eight months fooling around with them, draining it, taking it apart, sealing it with this, sealing with that. We finally got them sealed, but I can’t image how much that cost me.”

The experience resulted in a new approach to this feature: “Now when there’s an underwater window, I say, ‘We’ll do this, and we’re going to charge you this much, and there’s no guarantee,” he says. “I don’t own that window because I replaced a gasket.”

• Undersized plumbing: Always, always, always check the plumbing on an existing pool or spa before sizing a replacement pump. Look at the pipe that comes out of the ground and runs into the pump to see the suction-side size. It’s easy to overlook this, then promise a larger pump than the lines can accommodate.

McKenna has made it a rule that his salesmen must check this before selling the customer on a certain size pump. This information must be noted on the job paperwork so everybody down the line knows. “If [the salesperson] sells them a 2-horsepower pump and they have 1½-inch plumbing, you’re not doing them any favors,” McKenna says.