"Click" or Woodloc systems: there are a number of patented "click" systems that now exist. These click systems are either "unilin" or "fiboloc" A "click" floor is similar to tongue-and-groove, but instead of fitting directly into the groove, the board must be angled or "tapped" in to make the curved or barbed tongue fit into the modified groove. No adhesive is used when installing a "click" floor, making board replacement easier. This system not only exists for engineered wood floors but also engineered bamboo and a small number of solid floors (such as "parador solido click") and is designed to be used for floating installations. It is beneficial for the Do-It-Yourself market.
There are some characteristics that are common to each category: solid wood is more frequently site-finished, is always in a plank format, is generally thicker than engineered wood, and is usually installed by nailing. Engineered wood is more frequently pre-finished, has bevelled edges, is very rarely site-finished, and is installed with glue or as a floating installation. 
– If your floors are REALLY OLD and have been refinished many times, it may be time for a new floor. I’m not talking about oak floors that have been dinged and scratched up…I mean if your floors have been down for over 100 yrs and refinished at least 5 times. If you can see the “tongue” where the boards fit together, it’s probably time for a new floor. Or, if your floors are rather bouncy and/or don’t seem very sturdy, it’s time for a new floor. This happens more often with pine floors as pine floors are softer and used a long time ago. Denver Hardwood Floor
Solid wood flooring is milled from a single piece of timber that is kiln or air dried before sawing. Depending on the desired look of the floor, the timber can be cut in three ways: flat-sawn, quarter-sawn, and rift-sawn. The timber is cut to the desired dimensions and either packed unfinished for a site-finished installation or finished at the factory. The moisture content at time of manufacturing is carefully controlled to ensure the product does not warp during transport and storage.
Generally, hardwood floors need to be buffed every 3–5 years. The process usually takes about one day. Buffing refers to the process of using a stand up floor buffer. The floor is abraded with 180 grit screen on the buffer. This allows for the new coat of finish to mechanically adhere to the floor. This process works with great results as long as the floor hasn't had any waxes or synthetic cleaners.
– If your floors are REALLY OLD and have been refinished many times, it may be time for a new floor. I’m not talking about oak floors that have been dinged and scratched up…I mean if your floors have been down for over 100 yrs and refinished at least 5 times. If you can see the “tongue” where the boards fit together, it’s probably time for a new floor. Or, if your floors are rather bouncy and/or don’t seem very sturdy, it’s time for a new floor. This happens more often with pine floors as pine floors are softer and used a long time ago. Denver Hardwood Floor Install
So, assuming you can’t refinish existing and you can’t afford to replace it now, then focus on the new kitchen and put solid oak there. It’s okay and very common for this to be higher than the rest and it’s easy enough to add a wood transition. And, then later, you will need to replace the existing worn down floors w/ solid oak, so they will eventually be the same height. Denver Hardwood Floor Install
Michael – The exotic woods are a bit more challenging to work with stain wise because they are naturally darker and redder. Yes, you can refinish them and make them darker and browner. But, you will still have some underlying red tones. So, you may need to go darker than what you’re thinking to drown out the red more. Definitely test colors. Most likely, dark walnut will come out the darkest. Use duraseal…it’s a better stain, dries faster and is a bit darker than minwax.
While the overall thickness of flooring is going to vary by category, it is still important to know what is contributing to that thickness. Engineered wood flooring can inflate thickness by adding more layers of plywood or particle board, but still only offer a thin veneer of real wood on top. The dense core allows for Rigid Core floors to be significantly thinner than traditional hardwood floors, with WPC floors being thicker than SPC products. That doesn’t mean all Rigid Core floors are made equally though. Just like how engineered hardwood flooring can inflate thickness, Rigid Core flooring can alter the overall thickness by increasing the size of the acoustical padding on the back. While this padding adds a lot of great features, it doesn’t need to be any thicker than 1mm in size. When it comes to Rigid Core flooring, the thickness of the core is most important. Denver Hardwood Floor Install
Solid hardwood floor planks are made from a piece of wood and made to be anywhere from 18 to 20 mm thick. The boards are made with a tongue and groove to fit together for installation. Depending on the species of wood, certain floors will be harder than others. The harder the floor, the less susceptible it is to dings and scratches. The floor can be sanded and refinished several times to restore its beauty, with the total number of times being determined by the depth of the tongue from the top of the plank. Denver Hardwood Flooring
Width & Length – Plank flooring comes in a variety of widths and lengths. The most common widths are currently in the 5” – 6” range, but wider widths are rapidly becoming more popular. The length of your floor is also important to consider depending on the size of your space. Hardwood flooring comes in mixed lengths because imperfections are cut out of longer planks during production. Rigid Core flooring is built to size and comes in lengths ranging from 36” up to 80+”. Denver Hardwood Floor
Put on gloves, knee pads, and protective eye glasses. You'll be working diligently on your hands and knees for hours to complete this project, especially if you're doing a large space. Invest in a good pair of knee pads to protect your knees. Sturdy work gloves will protect your hands from splinters, and goggles will prevent sawdust and other debris from getting into your eyes. Denver Hardwood Floor
Besides major problems, you may also experience scratching or loose planks with your hardwood flooring. Scratches can be repaired with touch up kits, or something as simple as a like colored crayon. If you’ve got serious scratching, however, you may need to hire a contractor to refinish the flooring altogether. And if you’ve got loose planks, your only solution is to tie them down. Ideally they should be nailed to the subfloor to prevent any more movement, though excessively loose boards can be a sign of improper installation in the first place. Bringing in a professional hardwood installer to re-install your flooring properly is probably the only sure way to permanently solve the problem. Denver Hardwood Floor Install
It is difficult to compare solid wood flooring to engineered wood flooring due to the wide range of quality in both product categories, particularly engineered. Solid wood has some limitations. Recommended maximum widths and lengths are typically 5" / 127mm wide and 7' / 2100mm long. Solid hardwood is also more prone to "gapping" (excessive space between planks), "crowning" (convex curving upwards when humidity increases) and "cupping" (a concave or "dished" appearance of the plank, with the height of the plank along its longer edges being higher than the centre) with increased plank size. Solid wood cannot be used with underfloor radiant heating. However extra care is necessary with the planning and installation of the heating system and the wood flooring, such as limiting the temperature to 85 °F (29 °C), avoid sharp temperature fluctuations, utilizing an outdoor thermostat to anticipate heating demands, and monitoring the moisture content for the subfloor before installation. Denver Hardwood Floor
In general, it will almost ALWAYS be less expensive to refinish your hardwood floors. If you replace them, you need to pay for additional wood as well as ripping up and hauling away existing hardwood. If portions of your hardwood are damaged (e.g. pet stains or minor water stains), you can replace these sections and when you refinish them and it will all look new. Even if you have this, it will still be less expensive then replacing the whole floor. Hardwood Floor