Research methodology
How the Size Finder arrives at its numbers, where its allowances come from, and the specific questions it is not qualified to answer.
The sizing engine is deterministic
The same inputs always produce the same output. The engine performs no lookups, consults no clock, and uses no randomness. Each result carries an engine version so that a figure produced today can be reproduced and audited later.
Every inch added to a recommendation is attached to a named allowance with a stated reason, and the itemised allowances sum exactly to the stated minimum. There are no hidden adjustments.
Where the allowances come from
The clearance allowances are conservative planning values chosen to reduce the risk of a structure being too small. They are not manufacturer specifications and they are not engineering values. Roof equipment heights, slide-out projections, and frame geometry vary substantially between makes, models, and model years.
This is why the tool asks you to measure rather than relying on defaults, and why anything that comes from a default is labelled as an assumption in the result.
The height-basis question
Height is the dimension that causes damage when it is wrong, and the most common cause of a wrong height figure is that the number means something different from what the owner assumed.
Some manufacturers publish exterior height measured to the roof surface. Others publish height with roof equipment installed. Both conventions are in use. Rather than assuming, the tool asks which you have, and adds an equipment allowance only when your figure excludes equipment or when you do not know.
When roof equipment is added, only the tallest single item is counted. Items sit beside each other on the roof, not stacked, so a vehicle with two air conditioners is exactly as tall as one with a single unit at the same height. Summing published equipment heights is a common error that produces structures a foot or more taller than necessary.
What the tools are not
Nothing produced by this site constitutes engineering approval, structural certification, wind or snow load certification, zoning or permit approval, or manufacturer approval.
The tools help you arrive at a defensible set of dimensions before you speak to a supplier. The supplier, the manufacturer’s drawings, and your local building department remain the authorities on their respective questions, and we will not substitute our judgement for theirs.
Keyword and demand research
Our content priorities are informed by keyword data, but we distinguish carefully between what that data shows and what it does not. Google Keyword Planner returns bucketed ranges rather than precise volumes to accounts without active ad spend, so a figure such as 50,000 means a range rather than a measurement.
We do not present bucketed estimates as measured traffic, we do not conflate advertiser competition with organic difficulty, and we do not build pages for topics purely because a keyword tool suggested them. A topic being genuinely important to the decision is sufficient reason to cover it even when a seed list omitted it.