Repointing a shoddy paving job

[doobin]

Hi All,

First post here. Many thanks to Tony for a great site- always nice to see a guy who takes genuine pride in his work.

Right, so I have priced and won a right bodge of a job to sort. Essentially, it's uncalibrated Indian sandstone in a residental development. It was laid ten years ago, very shoddily. It varies between a half-arsed attempt at a full bed, and dot and dab, all with building sand rather than sharp, and varying strength of mix between reasonable to 'forgot to put the cement in the mixer'. Oh, and no sub base to speak of. Approx 350m2.

It's held together remarkably well considering. Last year they had it jet washed, and the gimp on the pressure rashed just kept going despite the pointing being blasted everywere! On the bright side, barely any joint raking needed.

After this, the resident's association (who we do a lot of work for) asked as to quote for repointing 'with a brush in resin compound' :laugh: :laugh: Having done a test patch a year prior ago (with an eye to doing the whole job) I sent them the following:

Please forward this email to everyone so the everyone understands the technical stuff behind both the problems and the possible solutions.

The pressure washing was not the cause- properly laid patio can be pressure washed ad infinitum. A properly laid patio is similar to a concrete slab- rock solid. The pressure washing simply washed out pointing that had already parted company with the slabs.

A path should be laid with a sub base (compacted granular fill, ie. Type 1/granite scalpings), a cement bedding layer, and then the slabs. As far as I can see, none of Budgenor's slab paths have a sub base.

Parts of your path are laid with four of five blobs under each slab, on the original soil. Other parts have a 'full bed' underneath, but as the slabs were not calibrated (this means sawn completely flat underneath), laying would require considerably more skill than was presumably available- hence a lot of slabs have cement underneath but this is only touching the slab in a few places. This is no better than the aforementioned 'dot and dab'.

Most of the paths are laid upon a building sand and cement mix. Building sand should not be used for laying slabs on- it is too soft, and moves too easily. Think of quicksand and you can understand how rain and ants wash the building sand away under the stones. Sharp sand is load bearing (due to the angular grit contained within it) and is the correct sand to use. Now, were this cement mix a decent mix then the use of building sand might not matter. However, it is almost all a very weak mix, and in parts no mix at all (just building sand)

What all the above means is that the slabs are free to move. However slight the movement, cement has no elasticity and this leads to the pointing breaking away at the sides. This has become progressively worse as the weak building sand mix has been washed way over the years. As I mentioned earlier, the pressure washer simply finished the job.

The 'bodge' to which I refer is the path on the left hand side as you exit the automatic gates, which I did as a test a year or so ago. A very wet mix was injected into the gaps with a pointing gun. This mix then gave support to the edges of the slabs where it was injected. The 'magic ingredient' in this mix was SBR. SBR is a polymer bonding agent, a waterproofer, and also adds a degree of flexibility into the mortar. It's uses are many, in particular laying thin screeds over existing concrete. In your application, these properties provide two things- one, that the mix will bond to the slabs far better. Two, that a small amount of flex (imperceptible to your eye) is allowed, hopefully (along with the extra support by injecting it down the cracks) preventing rocking and the pointing cracking away from the slabs.

The above is not correct practice, and I couldn't offer any warranty upon it's effectiveness. Were the base to continue to erode, the whole lot may again fall apart years down the line. However, the theory is (to my eyes) sound; it's relatively cheap compared to replacing the lot, and there is a test patch to examine which has been down a year. If the slabs laid upon dot and dab upon no base whatsoever are still relatively in place, simply missing the pointing, it sounds reasonable to presume that the above would go a long way to holding it all securely. It's only taking foot traffic, after all.

Now, whilst you have all the information above, there is simply no substitute for a site meeting, with me lifting some slabs and showing the committee for their own eyes the state of the underside. I would also be minded to try to lift some of the repaired section by the gates- test a slab or two to destruction even. If you could arrange a convenient time for the majority of yourselves, I should be delighted to meet you and demonstrate, either on a Sunday or of an evening.

I've since won the job and started work. It's going well- can highly recommend the PnuPoint gun- it's given us no bother and just works.

The mix I'm using is 3:1 with 200ml/kg of SBR, plus plasticiser and colourant.

Can anyone see any way to improve this bodge further?

Secondly, we occasionally (like one batch in five) have issues with cracks appearing after striking off. I'm mixing each batch in a bucket to keep it fresh, one bucket fills the gun twice over. Very sloppy mix, gets it right in there. It's not been too hot, and I'm loathe to wet the joints due to potential staining issues. I'm using 50/50 fast set and normal cement, as this gives us a good setting time for striking off. Any ideas?

[lutonlagerlout]

sounds like you are on the right track although using rapid set cement may bite you in the arse, also be aware you cannot really warrant any of it due to the possibility of further movement due to incorrect construction
not sure where you are but down south the sand does not go well through ointing guns and we have used easy point and larsen in the past with some success although micro cracking is always an issue with cement mixes,and some picture framing,although this goes with time

I find the SBR alone speeds up the cure time

cheers LLL

[doobin]

Thanks LLL. Yeah I made sure to say I couldn't warranty it in the email. Pure rapid set did indeed try to bite us in the arse- two buckets down then a frantic scramble to strike off and clean the gun and buckets all at once! So 50/50 seemed to work well, although I may cut the ratio down further as it warms up.

I've had no issues with the sand going through the PnuPoint. Had all kinds of trouble with manual pointing guns, and I'm always one to buy the best tool for the job which PnuPoint seems to be (so far anyway) We've found that a through mix is critical- next time we're on site I'm taking the plaster whisks to really cream it up in the final stage of mixing. The difference between the PnuPoint and a manual gun is that the air pressure is what pushes the mix out. With a plunger gun I found that the sand and cement tended to separate, but so far not an issue with the PnuPoint. Take your time to get the air pressure and the bleed off valve set right and it's a joy. It likes a really runny mix- the sort of mix that would normally drop out of a manual pointing gun. With the 90 degree bend in the PnuPoint this hasn't been an issue.

Picture framing- is that the white stuff that seams to 'sweat' out of the cement but brushes or washes off?

I considered a special gun injected pointing mortar, but reasoned that they are probably just a fine sand/cement mix with some co-polymer technology in them anyhow, so given the large amounts required and the eye on costs, an SBR-enriched strong mix would be most cost effective. We're using a lot deep into the joints, trying to 'underpin' the voids around the edges of each slab. Yes I know it's a bit of a bodge but it's the best I can see that we can do with minimal labour, which is the most expensive bit of any relay. The clients know us well and are on board with a bit of an experiment rather than a relay, having seen first hand the state of the original lay when you lift a slab. The test patch I did a year ago is still very solid, and it took a lot more effort to break a slab out as a test than to lift any other slab on site.

I went in at £15/m. Almost broke even on the first two days costing labour at £180/day, but there was a lot of joint raking and we were still finding our feet with the system. Biggest problem is having an air supply- can't run a decent compressor off an extension lead so it might be time to buy a petrol one. We used a 1.5hp filling a gas bottle as a reservoir, but it's pretty hard on the compressor.

Most of the rest of the job has very little mortar remaining in the joints, just a years worth of dirt which you pull out with a crack knife and then blow off with a blower. So I'm hopeful I might even see some profit. flip all point otherwise, eh?:laugh:

[doobin]

Just checked out Larsen Streetscape.

"It is manufactured from a controlled blend of specially selected fine aggregates, cements and additives and only requires the addition of water to produce a high quality pointing mortar for rigid construction methods."

Sounds like as I thought. £23 per 25KG. My mix is probably costing under £5 per 25kg. The extra cost on a job like this couldn't be justified.

On the petrol air compressor front:

https://www.ebay.co.uk/itm....iJQ9szE

Sorted! I have an LTS whacker- as I said in another post the anti vibe isn't great but the engine is a beauty. Just ordered that compressor.

[lutonlagerlout]

£15 a metre!!
I have loads of work for you :;):
good luck
as said elsewhere 2 part resin is the way forward
expensive but quick to install and bullet proof
LLL

[doobin]

£15 a metre!!
I have loads of work for you :;):
good luck
as said elsewhere 2 part resin is the way forward
expensive but quick to install and bullet proof
LLL

Bugger, what's the going rate? Spons pricebook reckoned £10/m on a new patio, so I added £5 on for cleaning out the old joints, which are 90% just dirt.

I try to price things about right to make money- basic Indian sandstone patio installed on a proper base I'd price at around £110+VAT per m2. Does that sounds right?

I hear you re 2 part resin, but with the voids under the slabs you'd use a tenners worth a slab and the base is still non existant.

[lutonlagerlout]

I tend to price according to the job,so many variables
we finished a job recently where everything had to be moved 100M down an alleyway
this increased the logistics massively
also depends on the size
20m2 patio wont cost the same rate as a 200m2 patio
in general rates are a dangerous thing to work from
if you lose money spons wont want to know
cheers LLL

[doobin]

I tend to price according to the job,so many variables
we finished a job recently where everything had to be moved 100M down an alleyway
this increased the logistics massively
also depends on the size
20m2 patio wont cost the same rate as a 200m2 patio
in general rates are a dangerous thing to work from
if you lose money spons wont want to know
cheers LLL

I find Spons to be a good starting point. They are very clear that site overheads need to be considered. When I first got the book I compared stuff that I know I make good money on, such as sleeper retaining walls, with their rates, and found them to be on a par. That gave me the confidence to use their rates as a starting point for other stuff.

Re taking mterials down an alleyway- can't recommend a MuckTruck Max with the flatbed carrier enough. Around £2k plus the VAT- will go almost anywhere, nice and quick and the simplest of labourers can use it and treble their productivity.

[doobin]

Roughly much would you price a 300m2+ repointing job at?

[lutonlagerlout]

Doobin
I never do ball parks,too many variables,once you get caught a couple of times,you learn
we did one a few years ago it looked straightforward so I went in at £25 a metre rake and repoint with easipoint
started grinding and the flags had been laid on ready mix with had squirted up between the joints
what we thought would take a day to rake out took 2 men 3 days and 4 expensive £70 diamond blades
then the client started to get unreasonably picky about the jointing
had priced for dinged,but they then wanted birdsbeak for the same money
so now I try and cover every eventuality on the quotes,and if they dont like the detail or price ,then " get someone else to do it " :;):
LLL

[doobin]

I like to have ballpark figures as a start point, so £150 for the Spons landscape pricebook was well worth it for me. Often, as on this job, I'll do a test patch to see what we're dealing with.

I learnt the hard way to make sure that the full spec is in writing in the quote:0

[Tony McC]

While they have the uses, you have to be exceptionally careful with the prices quoted in Spon's, and particularly the fantasy rates they use for paving work. I find many of their rates to be far troo low, and that is, I suspect, because they are based on the rates charged by labourers, jobbing builders and landscapers to do a "it'll-be-alright" job rather than the sort of money needed by a paving professional to do a quality job to a proper and compliant spec. The rate I saw for sett-laying was considerably less than I was needing to pay for quality work 10 years ago!

The 10 quid/m² rate for re-pointing a patio is the sort of money that's would be OK for a a brush-in or resin slurry job. Gun injection, cement mortar slurry or hand-pointing would need to be considerably more than that.

[doobin]

Thanks Tony. The £10/m Spons rate was for initial pointing upon a new lay, so £15/m seemed OK to me allowing for a small amount of raking on some joints and blowing out the majority of the rest. I googled everywhere looking for a typical rate for repointing a patio, but found nothing.

On the 'hardest' part of it I've covered my guys on a usual day rate, so the rest should be OK as hardly any raking. You pay to learn anyhow. :laugh:

Rates are a tricky thing, and every trade from tree surgeons to pavers is undercut in some way by people starting up. To be fair, I'm a 'jobbing landscaper' on this job but I always buy the best tools for the job and learn how to do it right- pavingexpert.com has been my go-to when asked to do a job.

Just given my new Chinese petrol compressor a once over- fitted a regulator and PCL XF outlet ports. It's rattly but will do the job for £320 with the VAT! Got it paired up with an old gas bottle as a secondary tank so should only need to run it once or twice a day for five minutes. Beats messing about with tiny compressors and extension leads or miles of airline.