Waterproofing Contractors | C-Link

Waterproofing Contractors

This guide provides a full review on the tips and considerations to make when procuring a waterproofing contractor. The guide broken down into sections: Tender Analysis, Value Engineering, Programming.

The Tender Analysis

Quotations received from multiple Subcontractors invariably have differences and it’s important to make sure you’re comparing Apples with Apples. Look out for these important ‘cross-checks’ to make sure you’re comparing like-for-like proposals.

1. Design Liability

With Waterproofing one of the major risks is liability: particularly in the design. When comparing tenders, ensure there is no split liability and that the final installation is covered for design, materials and installation by one specialist.

2. Guarantees

Guarantees are a mine field. Accept nothing less than one insured warranty, from one company, for all aspects of the waterproofing - covering the design, the materials and the installation. Many Guarantees are product guarantees, but consider - have you got a leak free basement guarantee? Product guarantees from the manufacturer only cover the value of the materials in the event of a claim.

3. Sequencing

All basement waterproofing systems will need to be carried in stages on site. Make sure all of your tenderers include for the same sequencing / quantity of site visits as required.

4. Inclusions

Basement waterproofing packages must include for an Internal Cavity Drain; floors; walls; a top of the wall detail which is critical to ensure a continuity of waterproofing from inside to the external DPC; deck Waterproofing and in some instances external waterproofing. Ensure all aspects are included for in each tender.

5. Preliminaries

This may sound obvious but with such a major design liability, make sure all tenders received include for adequate levels of on-going design and technical support, as well as the appropriate site and quality management resource to ensure quality assurance levels are met.

6. Quality Control

Have all specialist contractors confirmed included for an appropriate Quality Control / Assurance System on site. Specialists should complete regular site reporting with photos and diary, together with weather reporting for external works. Moreover, any Quality Assurance plan needs to consider sign off and handover, together with the appropriate site certification.

Value Engineering

This section identifies simple, intelligent solutions to Value Engineer waterproofing packages…

1. System Selection

In many instances there are more systems and materials built into a contract by manufacturers than is necessary to achieve compliance with insurance requirements; codes of practice and in fact, the British Standards. Consider the Grading of the building to ascertain Value Engineering opportunities.
  • For Grade 3 Habitable Buildings you require two systems of waterproofing for insurance companies to offer guarantees.
  • For Grade 2, you may only need one form of waterproofing but beware that Grade 2 for storage should be looked at very closely because different stored items require very precise environments.

2. Options, Options, Options…

Do you need external waterproofing and internal waterproofing? Do you need additives in concrete which double the cost? Always ask the Specialist what you need to achieve the insurance requirements. Also consider that external waterproofing can extend programme durations and be subject to delays due to bad weather: extensions of time can often be costlier than the waterproofing itself.

3. Pumped Systems

Does the proposed system come with multiple pumps and is this necessary? Do the pumps have backups and alarms? Important questions to consider are as follows:
  1. Has the contractor considered flow rates in his design? The duty pump (the one that does all of the work) should be large enough to pump effectively with a 100% spare, redundant capacity. The backup pump should be the same size and should be set to operate in the event of a failure of the first pump – is it?
  2. The inclusion of alarms for Pumped Systems is critical; however, alarms need to be installed where they can be heard so basement installation is often not the best solution – what is included and can a better location be found?
  3. Back-up Pumps come in all shapes and sizes but should have enough battery power to run until power is resumed or alternative power supplies can be utilised. What is included, and can this be value engineered?

4. Area Availability

Waterproofing is often completed in multiple site visits due to availability of areas on site. The waterproofing specialist will save time and setup costs on site by reducing the number of visits so consider, can you make larger areas of work available to allow continuous working on site to increase efficiency and decrease the costs? Be sure to check that all tenderers have included for the same minimum areas and visits.


Basement Waterproofing is a package of works that falls on the critical path of the project. Genuine focus and attention must be paid to this trade as often it kick-starts the project either on a successful or a difficult path. Follow these tips for a smooth delivery and handover…

1. Early Engagement

Basement Waterproofing is a technical and design driven package. Engage the waterproofing company as early in the design process as possible to best understand the risks and opportunities available to you.

2. Sequencing

Fragmenting the sequence of the waterproofing works can be time consuming and lead to inefficient working. Agree the areas that will be waterproofed at each visit as soon as possible and try to best coordinate this with any preceding trades to keep the waterproofing contractor on site for long visits.

3. Attendances & Preparation

Agree the preparation and attendance inclusions to be carried out by whom and when prior to the contract being signed. For example, consider the following key matters which will significantly impact the efficiency of the site installation:
  • Are there any noise limits restrictions?
  • Are there any working hours restrictions?
  • Who is responsible for concrete grinding for coatings?
  • Who is responsible for de-watering?
  • Who is responsible and how long should be included for surface drying?
  • Who is providing access equipment for working at height?

4. Pre-Start Meetings

It is paramount that a pre-start meeting is held with all package stakeholders – whether client, consultant or interfacing specialist trades. At this meeting all stakeholders need to be made aware of site constraints and requirements to ensure the programming and plan for the waterproofing is achievable and risks are removed ahead of commencement.

5. Weather Constraints

Consider the impact of the weather and the time of year the installation is being undertaken. Any external waterproofing will have set environmental requirements: normally dry surfaces require 3 above dew point but some require 5 above dew point and more. Does your programme suitably allow for covering, drying etc.?


This content was created in Collaboration with Maclennan, a leading Specialist in the supply and installation of waterproofing systems in the UK. MacLennan count among their staff qualified Civil Engineers, Quantity Surveyors, Waterproofing Designers and Electrical Engineers for pump design.