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Interlock base

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  • Jun 1st, 2021 7:09 am
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[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham

Interlock base

Need some advice here. I hired a landscaper to install a new interlock walkway and patio for me and I noticed he dug out probably 6 inches of soil, compacted the soil with his machine and it looks like he put down about 1.5 -2 inches of HPB (just roughly checked with my finger in the ground) and then then plastic netting type material before laying down the slab pavers.

I always thought you needed a minimum 3-6" of base? Feeling a little uneasy now. I specifically avoided other contractors who told me they only install a 2" base . He's been fairly professional and trustworthy so far so I didn't think to scrutinize the work on the day he was installing it until the next day when I noticed the pavers seemed very low relative to my existing wood deck skirting.

Do you think it is possible that it will be fine or am I guaranteed to have a settlement issue in a few years? He has another area to complete later so we can still have a discussion about it... but I imagine he is going to tell me how he installed it is fine and that he will refuse to do any rework.

He installed large format slab pavers if it makes any difference.
Last edited by dadapoet on May 24th, 2021 9:02 am, edited 1 time in total.
28 replies
Deal Addict
Apr 26, 2003
2318 posts
1385 upvotes
GTA
Since you got different quotes and didn't want to go with only a 2" base, was what you wanted noted in your agreement?
[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham
When we were talking about the job he mentioned a 6" base, unless I misunderstood something (e.g. remove 6" soil, and provide an unknown thickness of base). He didn't write down the base depth on the agreement, just areas of interlock. It's not a big job and a lot of people who quoted me were giving me very vague quotes like that with areas only.

So hard to find contractors in the gta who install based on industry best practices. Confused Face
Deal Addict
Nov 9, 2008
1852 posts
875 upvotes
Toronto
I'd be concerned with that little base.

I did ~10" of HPB. Definitely overdid it but nothing has moved in 6 years
Deal Addict
User avatar
May 18, 2004
2796 posts
429 upvotes
Ontario GTA
typical contractors.
i had mine say he was going to dig down 10" then when the actual day they ran into some roots (not a big surprise since it was next to a tree) and then without telling me he was there he quickly compacted and put in screening so it would be too late to complain saying it would be ok. digging 6 inches is really shallow in my opinion.
you will probably need to re-level in a few years, expect it after their "warranty" ends.

let it be a lesson for future contract jobs on this nature to have a sign off on the dig-out to the agreed level.
Deal Addict
Jun 26, 2019
2007 posts
1743 upvotes
GTA
Generally speaking you can't really quote a standard thickness of base material. Really, to do it right you should excavate until the bottom is not sitting on topsoil or material with more organics.

In a standard subdivision there is usually around 12" of topsoil, so you want to get through that.

This said, 2" is probably to little. If it was on a good native soil or well compacted fill, you might be fine. If it's a new subdivision and close to your foundation you're screwed.
Member
Feb 11, 2009
391 posts
132 upvotes
Some of the contractor use new construction techniques.

Google Alliance gator synthetic base. It's some sort of plastic or rubber base that speeds up installations...I saw my neighbor get that installed that way.

Whether it is good or not I don't know.
Deal Addict
Dec 14, 2011
1901 posts
1066 upvotes
London
I’m redoing mine because the contractor didn’t use edge restraint and my walkway has widened by about four inches, which is quite abit considering it is only four feet wide. Long gone are the days where men just did the job the correct way based on a handshake just because it was the right thing to do.
Sr. Member
Apr 10, 2019
517 posts
1084 upvotes
Ottawa
SubjectivelyObjective wrote: Generally speaking you can't really quote a standard thickness of base material. Really, to do it right you should excavate until the bottom is not sitting on topsoil or material with more organics.

In a standard subdivision there is usually around 12" of topsoil, so you want to get through that.

This said, 2" is probably to little. If it was on a good native soil or well compacted fill, you might be fine. If it's a new subdivision and close to your foundation you're screwed.
No 'standard' subdivision in North America has 12" of topsoil. If it did you'd be knee deep in mud every time it rains. I've been a developer for many years. Organics are scraped, trucked off and screened before any work begins. Then they truck some of it back for final grade and lay 6" if you're lucky to compact it to 4" but usually 5" compacted to 4"
[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham
My house is over 30 years old and the patio and walkway are maybe 12 feet away from the house, it wraps around the deck. I noticed he didn't use an edge restraint either....should I try to add one in by myself after the fact?

I'm at the point where I'm feeling a bit defeated and will just try to fix it myself in a few years if/when it goes out of level. It's really not a big area. Maybe I can try that gator board...I did see it at home depot. What else can I do now?
Deal Fanatic
Jun 7, 2005
9707 posts
1158 upvotes
I agree with what you said. I think our builder only put a few inches of top soil on the lawn.

Here is what Google says "There is no absolute rule to determine how required depth, however recommendations vary by use. The guidelines are 4 to 6 inches for pedestrian walkways and 8 to 12 inches for driveways. Local soil conditions also impact depth needs."
SubjectivelyObjective wrote: Generally speaking you can't really quote a standard thickness of base material. Really, to do it right you should excavate until the bottom is not sitting on topsoil or material with more organics.

In a standard subdivision there is usually around 12" of topsoil, so you want to get through that.

This said, 2" is probably to little. If it was on a good native soil or well compacted fill, you might be fine. If it's a new subdivision and close to your foundation you're screwed.
[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham
I talked to the landscaper today and he was surprisingly cordial about it and said he will raise the stone if that's what i want, but the stone will be higher than my grass (e.g. 2 inches higher?!) . I'm conflicted because it will help me achieve closer to the proper granular base thickness but it will screw up the grading and introduce tripping hazards which will be really bad for my young kids. I don't think he is going to dig down deeper plus add the right amount of granular base. Sometimes the fix is worse than the problem....

What do you think I should do?

(Also I'm not sure if he really meant it. He's the type who yells me he will come "Sunday" and then shows up 2 weeks later).
Deal Addict
Oct 20, 2011
1159 posts
436 upvotes
Mississauga
I didn't take the time to read through all the posts but when I did my walkway, I went with Unilock and installed it myself according to Unilocks recommended specs which are as follows.


"The base material we recommend is a locally approved road base gravel (6″ thick for a patio and/or walkway, 10-12″ thick for a driveway). On top of this compacted gravel a 1″ bedding course of coarse sand is placed prior to laying the pavers."

I ended up going with a couple if inches of 3/4" crusher run , then limestone.

I dug down 8 1/2" compacted.
laid down geotextile fabric, then couple inches of 3/4" crusher run, compacted.
laid down couple inches of limestone, compacted.
last layer was 1" bedding course, level then laid interlock.

Base was 5 3/4", bedding course was 1", paver was 2 1/4", for a total of 9". It's never been re-laid in 32 years.

When I did my driveway, I went down 18" and after 32 years, it's never been re-laid.
[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham
Is edge restraint mandatory for all installations? I talked to my contractor about it and he said edge restraint is only required for a driveway. He said my walkway doesn't need it. Is this true?
Deal Addict
Nov 9, 2008
1852 posts
875 upvotes
Toronto
dadapoet wrote: Is edge restraint mandatory for all installations? I talked to my contractor about it and he said edge restraint is only required for a driveway. He said my walkway doesn't need it. Is this true?
It will move without spiked in edging, or some solid edge for the pavers to but against (driveway, concrete etc. There should be an expansion joint between them).

That's two red flags for this contractor. Beware.
Deal Fanatic
Jun 7, 2005
9707 posts
1158 upvotes
dadapoet wrote: Is edge restraint mandatory for all installations? I talked to my contractor about it and he said edge restraint is only required for a driveway. He said my walkway doesn't need it. Is this true?
It all depends on how much you pay them as everything is additional cost LOL
Deal Expert
User avatar
Sep 1, 2005
18575 posts
13380 upvotes
Markham
The issue you have is...is there a misunderstanding? Is the pricing reflective of 2" base or a 6" base.

If materials alone don't make sense relative to the entire job, then you might want to pony up more $ and get him to re-do what's already done.
We're all bozos on the bus until we find a way to express ourselves...

Failure is always an option...just not the preferred one!
Deal Addict
May 18, 2015
1780 posts
802 upvotes
Ottawa,Ont
steph3n wrote: Some of the contractor use new construction techniques.

Google Alliance gator synthetic base. It's some sort of plastic or rubber base that speeds up installations...I saw my neighbor get that installed that way.

Whether it is good or not I don't know.
This--for others in the future. Gator bases are extremely strong and can replace some granular material. It does not sounds like OPs contractor is using one tho
[OP]
Newbie
May 6, 2008
48 posts
19 upvotes
Markham
I'm not an interlock expert and I really don't want to learn the ins and outs of how to install interlock just so that I can hover over someone and inspect their work and scrutinize their price. I really just want to hire someone for their expertise, let them complete their work in peace. But yeah.... here we are! I didn't know about tile edge restraints until someone mentioned it on this thread (thank you!) otherwise I totally would have asked for it in the quoting stage. I wasn't aware that it's required to install it vs a nice to have. I was just focused on the base thickness from the onset of the job.

Appreciate the feedback so far. I still don't really have an idea of how bad it will be in the long run but I also figure...its a stone patio at grade. It's not the end of the world whatever the results are... :(
Deal Addict
Jun 26, 2019
2007 posts
1743 upvotes
GTA
dadapoet wrote: I talked to the landscaper today and he was surprisingly cordial about it and said he will raise the stone if that's what i want, but the stone will be higher than my grass (e.g. 2 inches higher?!) . I'm conflicted because it will help me achieve closer to the proper granular base thickness but it will screw up the grading and introduce tripping hazards which will be really bad for my young kids. I don't think he is going to dig down deeper plus add the right amount of granular base. Sometimes the fix is worse than the problem....

What do you think I should do?

(Also I'm not sure if he really meant it. He's the type who yells me he will come "Sunday" and then shows up 2 weeks later).
Adding more base will spread the (point) loads out a bit more... which will put less pressure on the soils below, therefore making it likely to settle slower.

This said, if you have topsoil or organic material below the base of your patio, it will still settle overtime.

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