External vs Internal Basement Waterproofing

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Mar 15th, 2022 5:45 pm

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Mar 11th, 2022 2:07 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 2:07 pm

External vs Internal Basement Waterproofing

Hi all,

It`s me and my good ol' 100-year-old Toronto property again

. I was about to start finishing my basement when my contractor discovered leakages on the wall.

I've called several waterproofing companies.
Most suggested external waterproofing as the most effective way to prevent leakages. However, the legendary RCC just came and suggested internal waterproofing (using air-gap drainage membrane) instead with the following reasons:
i) My basement is unfinished at the moment and is the best time to do it
ii) It is effective and will not cause foundation damage nor mold as the water will be drained away to the weeping tiles. RCC offers lifetime warranty (they've been around for more than 100 years, so their warranty counts for something)
iii) It is cheaper and faster to do

He is one of the RCC owners (family run biz) and asked me to trust his expertise.
However, when I read RCC's brochure and website, they indicated that internal waterproofing should only be used when external restoration is not possible or to relieve hydrostatic pressure.

I've read many articles that advocated external waterproofing as the only effective mean to control basement leakages. So, I'm confused. I would like to hear RFDers' experience and opinion on this. Thank you.

Last edited by Ordeal on Mar 11th, 2022 2:32 pm, edited 1 time in total.

40 replies

Mar 11th, 2022 2:19 pm

chris416yyz: Deal Addict; Oct 25, 2017; 1194 posts; 1195 upvotes

Mar 11th, 2022 2:19 pm

External is better if you can achieve it. Internal is purely water management rather than waterproofing.

+16

Mar 11th, 2022 2:32 pm

kevin044: Newbie; Dec 2, 2019; 28 posts; 5 upvotes

Mar 11th, 2022 2:32 pm

I've had about 7 or 8 waterproofing companies come out with everyone having different opinions. RCC was one of them. I would suggest getting a few more waterproofers to come out so you can get other opinions.

+2

Mar 11th, 2022 2:42 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 2:42 pm

chris416yyz wrote: ↑ External is better if you can achieve it. Internal is purely water management rather than waterproofing.

That's what I told RCC but he responded that if the internal waterproofing could drain the water away without affecting the foundation, then it is the best solution for me. He added that even though he could have made more money doing external waterproofing, he still suggested interior waterproofing since my basement is unfinished.

Mar 11th, 2022 2:54 pm

torontotim: Deal Addict; Nov 17, 2012; 4857 posts; 4401 upvotes; Toronto

Mar 11th, 2022 2:54 pm

Ordeal wrote: ↑ That's what I told RCC but he responded that if the internal waterproofing could drain the water away without affecting the foundation, then it is the best solution for me. He added that even though he could have made more money doing external waterproofing, he still suggested interior waterproofing since my basement is unfinished.

Chances are this contractor isn't qualified to do the waterproofing period. Exterior is best - otherwise you're just continuing to draw water through your foundation and giving it a place to go.

If your boat was leaking, would you spend money on a pump to constantly remove the water instead of fixing the leak?

Have you already signed a contract for finishing your basement with a contractor and then realized there are water problems?

I'd be hitting the big pause button on any internal work, get out of the contract if you can and focus on waterproofing. Figure to spend 10's of thousands to do it right, either from the inside or outside. What is the footprint of the house (length/width)?

+5

Mar 11th, 2022 3:05 pm

engineered: Deal Expert; Feb 11, 2007; 19959 posts; 23539 upvotes; GTA

Mar 11th, 2022 3:05 pm

Ordeal wrote: ↑ That's what I told RCC but he responded that if the internal waterproofing could drain the water away without affecting the foundation, then it is the best solution for me. He added that even though he could have made more money doing external waterproofing, he still suggested interior waterproofing since my basement is unfinished.

Maybe he's thinking cost effectiveness for you?
What was the cost for external vs internal? If it's 100k vs 10k, that's a pretty easy choice. If it's 30k vs 25k, then it's harder.

If the women don't find you handsome, they should at least find you handy.

+1

Mar 11th, 2022 3:37 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 3:37 pm

engineered wrote: ↑ Maybe he's thinking cost effectiveness for you?
What was the cost for external vs internal? If it's 100k vs 10k, that's a pretty easy choice. If it's 30k vs 25k, then it's harder.

$15k ext vs $5k int

Mar 11th, 2022 3:40 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 3:40 pm

torontotim wrote: ↑ Chances are this contractor isn't qualified to do the waterproofing period. Exterior is best - otherwise you're just continuing to draw water through your foundation and giving it a place to go.

If your boat was leaking, would you spend money on a pump to constantly remove the water instead of fixing the leak?

Have you already signed a contract for finishing your basement with a contractor and then realized there are water problems?

I'd be hitting the big pause button on any internal work, get out of the contract if you can and focus on waterproofing. Figure to spend 10's of thousands to do it right, either from the inside or outside. What is the footprint of the house (length/width)?

I ve signed the contract unfortunately. The building size is 30 by 18 ft

Mar 11th, 2022 3:40 pm

grumble: Deal Addict; Mar 22, 2017; 2593 posts; 3528 upvotes; West GTA

Mar 11th, 2022 3:40 pm

External is far superior and usually far more expensive. Your call. I moved into a place that had one foundation crack that was internally waterproofed via injection and have had no water come from it whatsoever, though I'm unsure of the reason for its occurrence or if they did anything else to fix it. So it's possible it could work. External almost always works as long as there isn't some other issue like drainage, gutters, etc.

+3

Mar 11th, 2022 4:13 pm

SubjectivelyObjective: Deal Addict; Jun 26, 2019; 2013 posts; 1749 upvotes; GTA

Mar 11th, 2022 4:13 pm

Ordeal wrote: ↑ He is one of the RCC owners (family run biz) and asked me to trust his expertise.
However, when I read RCC's brochure and website, they indicated that internal waterproofing should only be used when external restoration is not possible or to relieve hydrostatic pressure.

Lets try and keep this short:

External waterproofing is the best form of creating an impermeable or near impermeable membrane. This is where I should note that in the foundation world, waterproof does not mean watertight.

In both cases, internal and external, the system must be designed to relieve the hydrostatic pressure. Your foundation was not likely designed to handle the full load of saturated soils. If 100 years old, so may be over engineered compared to todays standards, but probably was not that over engineered. In watertight foundations, they are designed to handle fully saturated soils loads and buoyancy, yes houses can float.

Therefore, in either case, external or internal, a weeper is required to connect into your free draining backfill material to alleviate the loads on your foundation wall. If you don't have free drainage material on the external wall, and your external weepers are blocked, this could potentially cause issues for the internal waterproofing approach.

In my own subjective opinion, external is superior to external waterproofing. You eliminate moisture from getting into your foundation, and you ensure there is free draining material to your weeper to reduce loads on the foundation. It is usually going to be more expensive as well, but in general is a better approach - this is not to say that internal is not comparable under certain circumstances.

If you have an old leaky foundation, with lots of cracks, fissures, etc, the water is freely penetrating, then internal is a viable solution. Just want to ensure that moisture is kept to a minimum and that there is no saturated soils against your foundation walls.

Hopefully that's fairly clear. There are a large number of factors in play, so it will differ from site to site.

Last edited by SubjectivelyObjective on Mar 11th, 2022 4:14 pm, edited 1 time in total.

+3

Mar 11th, 2022 4:14 pm

badass: Deal Addict; Dec 24, 2007; 1981 posts; 505 upvotes; Toronto

Mar 11th, 2022 4:14 pm

The only reason that I could think of is that your clay drain pipes are probably done as it’s a 100 year old home. Waterproofing and installing new drains inside would be the way to go.

I do agree that waterproofing from the outside is best but I guess he consider that your home is 100 years

Cheers.

Thread started in 2016 - 1927 fully gutted and renovated 2 storey detached home in the big T.O. - small projects still in progress.

RFD priceless!

+1

Mar 11th, 2022 4:43 pm

engineered: Deal Expert; Feb 11, 2007; 19959 posts; 23539 upvotes; GTA

Mar 11th, 2022 4:43 pm

Ordeal wrote: ↑ $15k ext vs $5k int

So it comes down to how much you can afford. Obviously external is better, but a well done internal job can do what you need it to. Tough call when external is 3x the price.

If the women don't find you handsome, they should at least find you handy.

Mar 11th, 2022 7:32 pm

mrweather: Deal Fanatic; Aug 29, 2011; 8830 posts; 5803 upvotes; Mississauga

Mar 11th, 2022 7:32 pm

There’s also the issue of accessibility. If they can’t dig down around the whole foundation perimeter, there’s no point.

+1

Mar 11th, 2022 8:33 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 8:33 pm

SubjectivelyObjective wrote: ↑ Lets try and keep this short:

External waterproofing is the best form of creating an impermeable or near impermeable membrane. This is where I should note that in the foundation world, waterproof does not mean watertight.

In both cases, internal and external, the system must be designed to relieve the hydrostatic pressure. Your foundation was not likely designed to handle the full load of saturated soils. If 100 years old, so may be over engineered compared to todays standards, but probably was not that over engineered. In watertight foundations, they are designed to handle fully saturated soils loads and buoyancy, yes houses can float.

Therefore, in either case, external or internal, a weeper is required to connect into your free draining backfill material to alleviate the loads on your foundation wall. If you don't have free drainage material on the external wall, and your external weepers are blocked, this could potentially cause issues for the internal waterproofing approach.

In my own subjective opinion, external is superior to external waterproofing. You eliminate moisture from getting into your foundation, and you ensure there is free draining material to your weeper to reduce loads on the foundation. It is usually going to be more expensive as well, but in general is a better approach - this is not to say that internal is not comparable under certain circumstances.

If you have an old leaky foundation, with lots of cracks, fissures, etc, the water is freely penetrating, then internal is a viable solution. Just want to ensure that moisture is kept to a minimum and that there is no saturated soils against your foundation walls.

Hopefully that's fairly clear. There are a large number of factors in play, so it will differ from site to site.

Thanks. I also thought that external waterproofing is the superior solution..
I would disregard the suggestion if it`s coming from any Tom, Dick or Harry waterproofers, but this is coming from RCC, the supposedly gold standard of the waterproofing industry...So, I`m undecided...

Last edited by Ordeal on Mar 11th, 2022 8:43 pm, edited 1 time in total.

Mar 11th, 2022 8:37 pm

Ordeal [OP]: Jr. Member; Nov 10, 2021; 124 posts; 21 upvotes

Mar 11th, 2022 8:37 pm

badass wrote: ↑ The only reason that I could think of is that your clay drain pipes are probably done as it’s a 100 year old home. Waterproofing and installing new drains inside would be the way to go.

I do agree that waterproofing from the outside is best but I guess he consider that your home is 100 years

Cheers.

Well, I did ask RCC a few times on why he recommended the internal solution and the reasons he gave were:
i) My basement is unfinished at the moment and is the best time to do it
ii) It is effective and will not cause foundation damage nor mold as the water will be drained away to the weeping tiles.
iii) It is more cost effective and faster to do

I'm still unsure if his justifications are valid..

Mar 11th, 2022 9:47 pm

engineered: Deal Expert; Feb 11, 2007; 19959 posts; 23539 upvotes; GTA

Mar 11th, 2022 9:47 pm

Ordeal wrote: ↑ Well, I did ask RCC a few times on why he recommended the internal solution and the reasons he gave were:
i) My basement is unfinished at the moment and is the best time to do it
ii) It is effective and will not cause foundation damage nor mold as the water will be drained away to the weeping tiles.
iii) It is more cost effective and faster to do

I'm still unsure if his justifications are valid..

Those are all valid reasons.
The only thing he left out was that it's not as good as external.
But external has its own issues.
- much more expensive
- may have issues with space/neighbours
- will take much longer
- makes more sense when the basement is already finished.

If the women don't find you handsome, they should at least find you handy.

+1

Mar 11th, 2022 11:56 pm

jacquesstrap: Deal Addict; Nov 9, 2008; 1852 posts; 875 upvotes; Toronto

Mar 11th, 2022 11:56 pm

If you have the ability to do it in the exterior, that will hands down be the best choice.

The only time you would typically do interior over exterior (other than cost savings) is if there are access related issues doing it from the exterior.

Interior is, as someone else has already mentioned, just a water management system. It does not prevent the water and moisture coming through your foundation, but simply directs it down and away from your finished substrates.

Exterior is the better choice. If you can afford it, do it right.

+3

Mar 12th, 2022 2:12 am

exrcoupe: Deal Addict; Apr 26, 2003; 2349 posts; 1417 upvotes; GTA

Mar 12th, 2022 2:12 am

I concur with all the votes for external. I got mine done with using the external method as well. I got a quote from RCC and they only suggested internal if the exterior did not have enough space or access to the walls. I ended up going with another company instead of RCC but both of them said that external is best

If you gave them a budget they might want to stay close to it also to get the job, but I doubt they are hard up for work..

+1

Mar 12th, 2022 8:59 am

random pattern: Deal Addict; Mar 29, 2008; 3897 posts; 1041 upvotes

Mar 12th, 2022 8:59 am

In an ideal world would you do both? Or overkill?

Mar 12th, 2022 9:27 am

jacquesstrap: Deal Addict; Nov 9, 2008; 1852 posts; 875 upvotes; Toronto

Mar 12th, 2022 9:27 am

random pattern wrote: ↑ In an ideal world would you do both? Or overkill?

You do not need both. Exterior will prevent water or moisture coming through your foundation, hence no need to waterproof / manage water on the interior.

+6

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