Why is there no single square metre price?
Most people asking for a waterproofing quote expect a clear unit price. But two basements of the same size require completely different systems if their ground conditions differ. The source of a price difference is usually not the profit margin, it is the scope of work.
1. Groundwater level
If the water table sits below foundation level, the water is not under pressure and a single membrane layer may be enough. If the water table sits above foundation level, the water is pressurised; a double membrane layer, drainage board and discharge system are needed together. This single variable can double the cost.
2. Whether excavation is possible
External application is always more durable but requires excavation. In terraced buildings, on narrow plots, or in gardens where the landscaping must be preserved, excavation may not be possible. In that case negative side waterproofing or injection is used from inside, and pricing is based on linear metres or the number of packers rather than square metres.
3. Condition of the existing structure
If there is active seepage, cracking or segregation on the surface, repair comes first. Concrete surface repair, crack injection and levelling are cost items that arise before the waterproofing itself begins.
4. Material class
The square metre difference between a membrane certified under TS EN 13967 and an uncertified sheet looks small on paper. The difference shows up in service life. Applications made with uncertified material have to be renewed within three to five years.
5. Number of detail points
Covering a flat surface is easy. What really drives cost is corners, pipe penetrations, expansion joints and changes in level. These points require separate taping and reinforcement. On a detail heavy project the labour share can approach half the total.
6. Access and site conditions
Getting material to site, hauling excavated soil away, machine access and restricted working hours all feed directly into cost. A basement in the city centre and a detached house with a garden are not priced the same way.
7. Warranty scope
A company that issues a written warranty takes on the risk and reflects that in its price. A quote without a warranty is always cheaper; when something goes wrong, the cost becomes a multiple of the original job.
What to check when comparing quotes
- Does it state clearly which system is being proposed
- Are the material brand and standard certification specified
- Are excavation, haulage and backfill included in the price
- Have the detail solutions been itemised
- Are the warranty period and scope written into the contract
Two quotes compared before these five items are clarified are in fact comparing two different jobs.
Why quotations differ so widely
Quotations for the same job sometimes differ by a factor of two. The reason is usually not that one is expensive but that the two cover different work. Before comparing, make sure the quotations cover the same scope.
How many layers of waterproofing? The difference between one layer and two is significant in both material and labour. One layer is not sufficient where the water table is high.
Is drainage included? Some quotations cover only the waterproofing item. Waterproofing installed without drainage works under constant pressure and cannot reach its design life. The cheaper looking quotation can mean paying for the job a second time a few years later.
Is there a protection layer? When the drainage and protection board is omitted, the membrane is punctured during backfill. This item is a small share of the total, yet omitting it wastes the entire job.
Are details resolved with separate products? Corner tape, sleeves and joint tape are separate products. If they do not appear in the quotation they will probably be improvised with the main material.
Who carries out excavation and backfill? Excavation, haulage and backfill are excluded from some quotations. These items account for a considerable share of the total.
Conditions that quietly raise the cost
Difficult access. A narrow street, the distance to a neighbouring building or a garden a machine cannot enter may force excavation by hand. The same square metre costs noticeably more than on a site with easy access.
Condition of the existing structure. Honeycombing, burrs or degradation on the wall face require repair before waterproofing. This item cannot be quoted without an on site survey.
No discharge point. If there is no chamber or natural fall for the drainage line to connect to, a pumping chamber is required. This decision changes the cost of the system.
Reinstating landscaping. Garden, pavement or car park reinstatement after excavation is excluded from most quotations.
The building being in use. Restricted working hours, noise and dust control and the need to work floor by floor all extend the programme.
The real cost of the cheap quotation
Waterproofing is work that gets covered by other layers once complete. Backfill at the foundation, screed and tiles on a terrace. For this reason mistakes surface years later, and putting them right means first removing everything above.
The cost of doing the job a second time is therefore not merely the cost of the first job. Stripping out, haulage, refinishing and the loss of use of the building during that time all count. The question to ask when comparing prices is this: does this quotation get the job done once?
Five things to ask for when requesting a quotation
The brand and type of products to be used, the number of layers and the target thickness. Whether drainage is in scope and which components it includes. A list of the separate products to be used for detail work. Who is responsible for excavation, haulage, backfill and landscaping. What the guarantee covers and which situations fall outside it.
Once these five headings are clear, quotations become comparable. Until they are, what you are comparing is not price but two different jobs.