self build waterproof basement formwork membrane concrete benefits

Benefits of Waterproof Concrete
and the benefits of using my waterproof concrete admixture rather than anyone else's.

Waterproof concrete does not let water in or out:
  1. Water cannot get through. Depending on the exact concrete mix it might be that no vapour could get through either, but there isn't a test for vapour transportation through concrete that I know of.

  2. Waterproof concrete cannot dry out over time. Drying shrinkage is the major cause of cracking in old concrete. Waterproof concrete cannot dry out so it cannot crack for that reason. That is why waterproof concrete should never crack.
  self build basement
  1. Most chemicals that are deliterious to concrete, such as sulfates, salts and oxygen, need to be dissolved in water to do harm. Since the water cannot get in neither can the deliterious chemicals.

  2. In basement construction, waterproof concrete meets the requirement in BS8102 that the first defence against ingress of water should substantially reduce the amount of water that internal drainage (if chosen) has to deal with.

Waterproof concrete can be made with pure OPC, OPC blended with PFA or OPC blended with GGBS. These are known in the UK as CEM1, CEM2 and CEM3.

Waterproof concrete generally has 350kgs of cement. 350kgs of pure OPC is good for DS2 sulfate resistance, which is almost always sufficient. GGBS or PFA replacing part of the OPC should give class 3 and class 4 protection. Check with your concrete supplier what cement blends he can offer you.

Most customers want their waterproof concrete STRUCTURE not to leak. But other suppliers of waterproof concrete admixtures only "guarantee" that sound concrete won't leak, which is worthless since sound concrete is inherently water resistant even without any admixture, see the reference below.

Clients want a structure free of leaks. Leaks can be through joints, voids, cracks or debris where it wasn't cleaned. Leaks aren't usually through concrete. Leaks are through spaces between pieces of concrete. Clients want none of these spaces.

The Concrete Society, report referenced on the architect page, quotes as follows (at 7.1.1.):

" In its introduction to the selection of materials the publication Concrete Basements Guidance on the design and construction of in-situ concrete basement structures to the Eurocodes (The Concrete Centre, 2012) states: "Good concrete is inherently water resistant".

It then goes on to say;

"Before considering selection of materials, it is worth emphasising the fundamental requirements for achieving such performance. These are:
  • correct structural design
  • appropriate concrete mix
  • good workmanship in construction
  • appropriate supervision.
Many water-resistant basements have been successfully constructed on the basis of the above alone. There are a number of admixtures in the market to modify the properties of the fresh and hardened concrete (e.g. porosity, permeability). Such measures should not be necessary if the basic principles noted above are observed."

The 4 bullet points just above are worth reading again.

Successful waterproof concrete needs
  • correct structural design
  • appropriate concrete mix
  • good workmanship in construction
  • appropriate supervision.
The concrete is only a quarter of the requirements.

You only have to read the news about towers that burn and houses built with many faults to know that good workmanship and supervision are very rare.

I supervise concrete and I have a method that improves workmanship.

No basement with my admixture, my fibreglass rods and, most important, my supervision since 2013 has had any leak through the concrete structure. Not through concrete, joints or voids.

I don't make you buy any expensive tapes, strips or membranes. You can rely on the concrete alone.

My methods and my products allow me to guarantee YOUR work because I know your work will work.

I was at this site to supervise the concrete pours, they used my rods and I put my admixture into the concrete.

Most of my clients employ a team directly to build the basement they will live in. You can see in this photo
  1. Lots of reinforcing steel, evenly spaced, neatly tied, clean beneath - correct structural design

  2. A very dense and cohesive concrete obviously not over watered - appropriate concrete mix

  3. a concrete pump to place the concrete where it needs to be, air driven poker as well as vibrating screed bar, hose pipe being deployed to spray water to cure the surface properly. The air compressor will be used with a pole scabbler to scabble the wall joint concrete before the wall formwork goes up - good workmanship in construction

  4. and on the top looking down - appropriate supervision
All 4 bullet points met in full.

basement slab

Neither are they forming kickers, the timber is for a drainage channel around the inside.

Waterproof concrete is a good concrete fit for purpose AND good workmanship. Not just one or the other.

Question. What would you normally get from a contractor using what your architect or structural engineer specified?

Answer = LEAKS

  1. The kicker your structural engineer specifies will leak badly

    because the contractor will use concrete a few hours old that is too stiff to compact because he needs to wait until the slab concrete is stiff enough for the kicker not to sink into it.

    This photo was taken of a basement built 6 years ago that has to be substantially repaired. The estimate just to stop the otherwise "WATERPROOF" concrete leaking through poor joints, holes and voids is £8,000.

    It is likely that at the end of the slab concrete pour they dumped some concrete on the floor somewhere then carried it in buckets to form the kicker a few hours later. You can see they scooped up bits of wire and other rubbish with it.

    I can promise you that no branded waterproof concrete admixture supplier will give you a waterproof concrete guarantee that covers poor workmanship.

    If you use all my products as appropriate and your team listens to me when I attend the concrete pours I will fix any leaks through the structure for free. My methods mean there has not been any leak to repair in any basement I was paid to help build since 2013. I can save you a lot of money and grief.

    leaking kicker

    I have a page about how to succeed without a kicker here.

  2. The holes deliberately left through the waterproof concrete wall will leak.

    Will there be holes? Yes. Hundreds of them. They might get a rubber bung or even a repair but a few will be missed. The contractor just left the holes through these walls. The client bought the rubber bungs later but they didn't work.

    holes through basement waterproof concrete   hole through basement waterproof concrete

    Every hole is lined with a plastic sleeve, because that is what all contractors use. The sleeve means they can recover their steel threaded bar to use many times.

      waterproof concrete tie bar plastic sleeve

    Years ago I was asked to visit the new home being built for a Professional Football Player in Cheshire.

    The holes through his basement were all filled but some still leaked.

    The water could be getting in through the plastic sleeve past the repair, or it could be getting in past the outside of the plastic sleeve because the concrete does not bond to smooth plastic pipe.

    The biggest expense wasn't re-filling the holes. It was ripping out all the decorated plasterboard in front of where the water was appearing and continuing along the wall ripping plasterboard down until the sources of the leaks could be found.

    Then doing the plasterboard, the finishing plaster and the decorating again.

    They told me this was Caltite concrete.

      caltite leak

    You can buy expensive hole repairs that are quick to use, such as expanding sodium bentonite clay plugs, but they don't stop water getting past the outside of these tubes. Your labourer could miss a few plugs out and put a few more in wrong.

    I was able to push about a quarter of the tubes out and the rest I drilled out. Drilling each one took 8 minutes. This is one of 400, so they took 2700 minutes to get them all out. That's 6.5 man days or about £650.

    Next I put a plug of concrete mid way along the hole and 2 days after that I ram concrete in from both ends.

    Finally I paint each side with 3 coats of waterproof paint.

    400 holes took about 12 man days to completely seal with absolute confidence. 33 a day. £3 each.

    The black paint is useful because it is a thorough and simple visual check that a hole repair has been completed.

      leaking tie bar hole drilling

    I can sell you a fibreglass threaded rod and a nut to go on each end. The rod is cast in the wall and the ends cut off later. They do the same job without a leak, and I can hire you the steel waler plates.   FRP threaded rods and nuts tie bar concrete formwork

  3. The swelling strip will not work, and the joint will leak;

    It is far too difficult to fix a swelling strip properly and continually to the substrate.

    It is far too difficult to butt the tape ends together properly.

    The contractor will be in a rush to get the work done and paid.

    You won't know about these errors till you move in and discover water.

    The tapes are a mix of rubber and a special clay (sodium bentonite) that swells to about twice the volume when it soaks up water.

    The clay swells and the rubber stops the leak.

    As if being too difficult to fix properly wasn't bad enough. If it rains before the concrete goes in the tape swells early and rips itself off the fixing as it doubles in length.

    waterproofing strip failing in rebate

    The result every single time is that somewhere at least, or more probably almost everywhere, the tape will not be in the joint between two bodies of sound concrete so it cannot do its job.

      swelling joint strip

    In the example above, the next concrete will get between the tape and the joint so the tape will not be in the joint where it could swell.

    And this stuff is incredibly expensive - and profitable. Your contractor will want you to pay for miles of it.

    I have a page about how to form waterproof joints properly here.

  4. The membrane stuck on the outside will not stick properly, and leak.

    When you are shown some sticky back membrane and see how well and quickly it sticks you will be amazed.

    1. Out the ground, and especially in an architect's office, it sticks instantly.

    2. In fact, it can stick instantly to everything and itself which means it is hellishly difficult to get a flat membrane on a flat wall without it creasing up and becoming useless.

    But the real issues are

    1. When you finally get the membrane spread out all over your concrete blinding and you fix your steel and pour your slab, you then have to pick up the ends that have been trampled half to death, get them scrupulously clean and hope that when you peel off the paper the strips stick together. They might stick in most places but that crease up from under the slab won't. If you don't have waterproof concrete and water can get in a tiny hole at the bottom corner of your slab concrete then your slab concrete will always be saturated and the sticky back membrane was a waste of money.

    2. Beneath ground, on the north side of a basement that never sees the sun, the atmosphere will be damp and sticky back membrane just doesn't stick any more. Not even if you prime the walls first as directed.

      If you are being shown how brilliant this stuff is in someone's office. Put the kettle on and let it boil with the lid removed. A bit of water vapour and this magnificent product will lose all its magnificence. It will lose all its magnificence down the north side of your basement as well, and be a very expensive waste of money.

  5. The concrete will have voids that will leak.

    Please remember. I am discussing what contractors do, not what you will do with my help.

    Because you will pour your wall in two goes, bottom then top, you will get your concrete to the bottom of each form in much better condition and you will compact it properly much more easily.

    basement leak 1   basement leak 2   basement leak 3   basement leak 4   basement leak 5

    That is why you won't have any photos of poorly compacted concrete like these above if I help you.

    Neither will I let you or your team not bother to clean a layer of dust or dirt out in the bottom of the wall formwork before you pour concrete. I will have explained how to clean it and I will refuse your concrete if it is not clean.

    This joint had been leaking for 6 years. You can clearly see where the soil from the excavation that had collected in the wall formwork had washed out over that time. To prove my suspicion, I chiselled out as far as the reinforcing steel and with an air compressor to clean the site I found the local red soil still there, still leaking.

    leak at the base of a basement wall   leak at the base of a basement wall investigated sand found

    No expanding tape or strip is going to stop a layer of soil letting water through.

  6. Water will get in over the top of the retaining wall if the retaining wall has a flat top that stops beneath outside ground level.

    Specifiers often aren't used to designing basements. They want the ground floor to be a normal ground floor which might mean beam and block. But great care needs to be taken to ensure that the waterproof retaining wall extends to above outside ground level, otherwise there will be an ingress of water horizontally over the retaining wall beneath the construction above.

    I have a section on my page for architects that explains why beam and block, precast concrete planks and corrugated steel decking will all fail when they are the floor over a basement.

  7. The internal drainage, sump, pump, backup pump and backup power supply will fail and your basement flood.

    Not because any of these components will necessarily fail but because the pipework getting rid of the water will fail.

    basement sump pumping   You can buy a chamber with everything you need including a loud alarm if the pump isn't working.

    But when the pipe up your basement wall to the outside splits at a joint your basement floods without the alarm sounding because the pump still pumps.

    You need to plan your basement to be dry without relying on any membrane with a life of only 60 years or any pipework whose life might be less than 10 years.

    The only waterproofing measure that lasts hundreds of years is waterproof concrete poured properly.

If you are reading this page because you are planning a basement that is for you to live in, you shouldn't think you have any other choice but to use me to help you build it waterproof from the start.

basement construction menu page   At the foot of every page you will find this image. Click it to go to our menu page where every page is listed.

Clicking the banner at the top will return you to the home page.

 Previous Page

why not icf

 Next Page

bare concrete walls

 The Page After That

basement information