A few thoughts and tips on laser scanning for Revit MEP Modelling
Over the last few years our scanning and Revit modelling skills have been increasingly called upon to help record MEP (mechanical, electrical and plumbing) systems in buildings. It’s an area often overlooked; most commentary on scan to BIM tends to concentrate on how architectural detail has been scanned and modelled, so I thought I’d write few words based on our experiences which may be of help to others.
It’s now more than 8 years since we handed over our first survey in the form of a Revit model, and up until just 2 or 3 years ago the models we produced were pretty much just architectural with no MEP at all. There was great reluctance for many working in the MEP sector to make the switch to Revit as many felt that its MEP tools just weren’t yet as good as the ones they already had available elsewhere. Things have changed enormously over the last few years though with greater BIM adoption and an insistence from main contractors that everyone working on a project are on fully compatible software systems – and more often than not that means using Revit.
So what are the key things we’ve learned and what advice do we give clients who approach us about a scan to BIM project that involves some MEP modelling?
- If you don’t need it, don’t model it! We often get asked if we can model detail down as far as every single cable running through a building and every tiny pipe supplying the wash basins. Well, we can scan and model all those things if necessary, but are they really necessary? Modelling the MEP in a building often takes longer than modelling the building itself. If cables and small pipes are going to be ripped out or will remain unaltered than they may not really need to be modelled, which can save a lot of time and expense. The same can be said for larger items that are being removed or will not be altered – exclude them from the model if they’re not needed. Don’t worry if requirements change over time. If something that was excluded at the start needs modelling at a later date it’ll already be scanned so it can easily be added to the model without the need for another site visit.
- Level of Detail – get it right! MEP systems always have brackets supporting them, valves and meters along their routes, they run through switchboxes and have an assortment of other attachments that often make them complicated to model. Complicated models take a long time to produce and they can easily become too large to be of practical use. So get your LoD (Level of Detail) sorted before you start. Always go for the simplest form you can. Concentrate on modelling a pipes route and diameter for instance, rather than modelling a hundred hangers attaching it to a ceiling. Where possible set limits on the size of services to be modelled – e.g. are pipes smaller than 50mm really needed for this project? Model plant as simple blocks instead of showing every detail. The trick is always to simplify everything as much as possible. It’s important that both the surveyor and the client understand exactly what’s required and exactly what’s going to be delivered.
- Use Webshare to see what’s really going on around an MEP system. Faro Webshare (or similar products such as Leica’s TruView) can give a 360 degree photographic view that lets the user examine every tiny detail of the area that’s been scanned and to quickly measure distances and areas. Make sure a Webshare is part of the deliverable and that everyone is trained in its use.
- Give careful consideration to where your MEP systems are situated. One of the most common areas to run the MEP systems through a building is above suspended ceilings. To scan these systems the surveyors either needs to have all the ceiling tiles removed beforehand, or individual tiles have to be removed and an elevating tripod used to lift the scanner up into the ceiling void. In order to ensure everything in the ceiling void gets scanned it’s always best to remove the whole suspended ceiling first – although this is often impractical. Either way, to make this process efficient and prevent any damage to the ceiling, the lifting and replacing of tiles should be always be carried out by a contractor supplied by the client. Don’t forget, older ceiling tiles may contain asbestos, as can pipe lagging and some electrical systems – always make sure all staff are trained and they have seen the building’s Asbestos Register before work starts so any necessary precautions can be taken.
- As has been mentioned before, modelling often MEP takes a lot of time. There are now some tools available now that can help the modelling process by automatically extracting pipes and ducts from a point cloud but in general most of the modelling still has to be done manually. If time is critical then always aim to get the architectural part of the model issued first, separately from the MEP model.
- Get the surveyors to work closely with the MEP team. It’s never easy to identify exactly what some systems running through a building are. Many pipes have no markings on them and hot and cold air ducts may look exactly alike. Surveyors are seldom MEP experts so having advice close at hand from those who are will assist in making the model more comprehensive. If expertise is not at hand then it’s best to model systems as generic types and change them at a later date.
Just a few thoughts and tips – I hope you find them useful!