No Mechanical Floor Plans? Locating Utilities Inside Below Slab on Grade

April 9, 2020
Tenant improvements and renovations are a huge sector of the construction industry. Contractors regularly acquire a space and then require finding and connecting to the existing 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..

Recurring Problems..

At Xradar, scanning concrete slabs is what we do. We regularly scan slab on grade in order for clients to safely trench for installing new plumbing below the slab. However finding the existing utilities below before trenching is paramount.

No point trenching in the wrong place!

Xradar has scanned numerous proposed trenches for clients only to find that the pipe they are trying to connect to:

1. Is not where it’s supposed to be.

2. Is not deep enough for the contractor to make the grade.

3. There is another conflicting utility or footing in the path to the connection.

In some situations clients have proposed trench lines for washrooms that tie into storm drains! 

Therefore it is much better practice to know the existing layout of all the utilities then plan the floor trenching from that.

Sub-Slab Utility Plan

We combine Xradar ™ concrete scanning with 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, on site! 

Using this clients can plan and layout their trenches, avoid conflicts and then  most importantly safely cut the slab to tie into them all in one service!

Saves Cost & Headaches!

- Perhaps there is a much shorter route for the line saving concrete cutting, material and labour costs?

- 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. 

- Avoid splitting rebar lengthways while cutting, this greatly improves cutting efficiency and cost. 


Q - Why not only do 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 the two gives you the best of both worlds. 

Q- Why is it useful to locate the plumbing below the slab? If I have scanned and cleared the slab for cutting?

A- Often where you’re told the sanitary line is, isn't always correct. People mistake storm drains for sanitary drains. People cut their utility trench only to realise there is a waterline or electrical  in the way of their proposed sanitary line. Similarly the depth of the sanitary line where they had proposed to tie in isn't 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 you can take to tie into saving you cutting that big trench across the room when you don’t need to. 

Q - Does it cost extra to produce the sub-slab utility plan?

A- There is no specific extra cost for the utility plan sketch, it just adds a small bit of site time as we complete it onsite and include it in our report which we 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 as we have to utilise different equipment and techniques.