Locating Subsurface Utilities Inside Buildings
Tenant improvements and renovations are a huge sector of the construction industry. Contractors regularly acquire a space and then require finding and tying into the existing utility services below the slab.
Depending on the age of the building, as-built plans can be limited or even non-existent! Even in brand new buildings things aren’t always what they seem.. GeoScan locate utilities inside buildings and can generate as-built drawings and floor plans, or a full subsurface utility plan, before you trench.
Recurring Problems
At Geoscan we regularly utilize Xradar™ Concrete scanning to scan slab on grade, in order for clients to safely trench and install new plumbing below the slab. However, finding the existing utilities below before trenching is paramount.
Don’t waste time and resources trenching in the wrong place!
Geoscan has scanned numerous proposed trenches for clients, only to find that the pipe they are trying to tie into:
- Is not where it was anticipated to be
- Isn’t deep enough for them to make the grade
- Has a conflicting utility or footing in their path to it
In some situations we’ve witnessed proposed trench lines for washrooms that tie into storm drains!
Therefore it is much better practice to know the existing layout of all utilities before planning the floor trenching.
Sub-Slab Utility Plan
We combine Xradar™ concrete scanning with our low frequency GPR (Ground Penetrating Radar) and EM (electromagnetic) utility locating methods to identify the layout and route of all the utilities below the slab. We can then digitally overlay our findings on an existing floor plan, whilst on site!
Using this, clients can plan and layout their trenches, avoid conflicts, and then most importantly safely cut the slab to tie them all into one service!
If you want to learn more about the applications of Ground Penetrating Radar, read our summary article.
In Summary – Save money and headaches
It’s worth considering that there is a much shorter route to cut costs whilst planning utility lines.
Here are our points to consider:
- Plan ahead to understand what you’re working with can save you time, money, and stress
- You certainly shouldn’t and don’t want to be cutting through footings or thickenings
- Avoid embedded conduits as well as pipes and conduits below the slab when cutting and trenching
- Try not to split rebar lengthways while cutting, this greatly improves cutting efficiency and cost
If you have a project that you need advice on, or need a utility locator, please get in touch with our team of experts and we’d be happy to talk you through your options.
FAQ’s
Q – Why not only use GPR for a utility locate?
A – Utility locating GPRs operate at low frequencies meaning they can penetrate quite deep, however the resolution is poorer. You are unable to accurately mark out rebar and embedded conduits in the slab using a utility GPR. A high frequency concrete scanner provides a much better resolution at shallow depths for finding things in the slab or just below. Combining this with EM gives you the best of both worlds.
Q – Why is it useful to locate the plumbing below the slab if I have already scanned and cleared the slab for cutting?
A – Amazingly, you’re often given the incorrect location of a sanitary line. People tend to mistake storm drains for sanitary drains. People cut their trench only to realise there is a waterline or electrical in the way of their proposed sanitary line. Similarly, the proposed sanitary line link isn’t deep enough for them to make the grade. Often the full route of the line isn’t known, meaning there may be a much shorter route available. This would save you from unnecessarily cutting that big trench across a room.
Q – Does it cost extra to produce the sub-slab utility plan?
A – The sub-slab utility plan adds a small amount of site time on site, but there is no specific extra cost. We complete the report onsite and include it in our report, which our RULT will send upon leaving.
Q – Can you Locate footings?
A – If the footing is flush with the bottom of the slab, then yes! If it isn’t, it IS still possible, just a little tricker.
Q – Is this a CAD drawing of the interior utilities?
A – This isn’t typically supplied as a CAD drawing, but a CAD drawing and 3D walkthrough of the utility layout can be priced and supplied if required. Further information about our utility reporting can be found here.