Doing one's "levels".

[epsilonGreedy]

As a prospective hands-on self builder the two most frequent questions I am asked are:

 

1. Who is your main builder?
2. Who will be setting out for you?

 

The answer to both questions is = me. I am not troubled by the intellectual or practical challenge of setting out the plan view of my house but "doing levels" remains a mystery. I have a prescribed ridge height with my planning permission and lack of gradient for the foul drain is of more concern than too much gradient. On the positive side the max height delta across my foundation plan is 300mm according to my diy water level survey.

 

Can anyone point me to a tutorial on doing levels for residential property setting out or a YouTube video?

 

Other info:

 

• Building control diagrams are being prepared.
• Foundations will be trenchfill and a beam & block floor.

 

p.s. I understand that step one for the digger man will be to create a level area prior to digging the trenches.

Edited June 13, 2018 by epsilonGreedy

[ProDave]

The first thing you need is a reference to work from that will not change throughout the build.

 

If you have something you can reference to on Ordnance Survey level that is great. Otherwise you create a Temporary Bench Mark that remains in place and everything is referenced to that.

 

In my case there was a substantial fence post at the highest corner of the plot so I created a permanent "mark" on that by banging in a row of horizontal large head (roofing felt) nails about 100mm above ground.  That became my Temporary Bench Mark and is still there now.

 

All my planning drawings referenced site and building levels relative to that TBM

 

In your case depending how your ridge height limit is defined, you must "callibrate" your TBM so you know how far above it is your ridge height limit.

 

Once you have the TBM you take all your levels from there by any means you like including the water level.

[MikeSharp01]

Yes at least one fixed point is vital. I am now finding I need several as the total station (TS) cannot see everything from one place so I have created a couple more fixed points and associated back sights over which I can set up the TS and know where it is in X/Y and use the back sites to get the Z and angles to the grid. There is no ridge height fixed, by planning, our build but the eaves line is fixed and so determines all else.

[Brickie]

Have you looked on OS map to see if there’s  benchmark near you? Commonly found on Churches or other historic buildings-somewhere considered ‘permanent.’

[PeterW]

6 minutes ago, Brickie said:

Have you looked on OS map to see if there’s  benchmark near you? Commonly found on Churches or other historic buildings-somewhere considered ‘permanent.’

 

Or look here Bench Mark database

[Jeremy Harris]

Worth looking around in the road, too.  We noticed a spot height on the OS map that seemed to be in our lane.  A quick look revealed a survey nail and washer in the lane right next to where our drive was going to exit, with a height of 81.48m AOD.  We referenced everything from that nail, which made things nice and easy.

[epsilonGreedy]

Thanks all.

 

Assuming such a reference height can be translated to a corner of my house foundation, what next?

 

The approved plan shows a spot topographical height for DPC at one corner of the house and further heights on the elevation diagram up to gutter height. From this info I will be able to calculate how much of the soil at the high corner of the house footprint needs to be removed but how do I indicate this to the digger man? I have seen some sites marked out with coloured stakes within the foundation foot print, are these higher/lower hints to the digger operative?

 

Following this and assuming I have a level soil plinth it then seems quite rudimentary to observe the trench dig and ensure all are about 1 meter deep. Is there any need for laser cross checks at this stage?

 

Finally in my mind I will need some height stakes bashed into the bottom of the trenches at say 2m intervals to provide a concrete fill level. This stage seems critical and a job for someone with a laser level?

Edited June 13, 2018 by epsilonGreedy

[Brickie]

On your approved plan does it show the heights as a height above Ordnance Datum? E.g. 77.6 AOD. If so,this would suggest a nearby datum exists. 

Regarding your trenchfill,the groundworkers I know use a laser level with the beeping audio on the receiver & an ‘elephants foot.’

This is basically just an upside down ‘T’ shape in 4x2 timber,around 1.8m in height. The receivers are designed to be fixed to surveyors staffs so can easily be fixed to the 50mm side of a 4x2. They set the level & receiver so the underside of the elephants foot is at the desired height for the concrete & check it as it’s poured. It’s not 100% accurate as the timber can sit down a bit in wet concrete but is near enough for footing concrete. 

[epsilonGreedy]

2 hours ago, Brickie said:

They set the level & receiver so the underside of the elephants foot is at the desired height for the concrete & check it as it’s poured. It’s not 100% accurate as the timber can sit down a bit in wet concrete but is near enough for footing concrete.

 

 

I prefer this method because the idea of leaving a swell-able piece of height indicator timber embedded forever in my foundations just feels wrong. My DPC will be higher than usual due to  minor flash flood concerns which means even with trench fill there will be a few extra courses of bricks to adjust out a small error in the foundation concrete height.

[Russell griffiths]

If you are building a lot of this yourself

i would go and get a rotating laser and receiver 

most of the trades you employ will have one with them, so if you are going to do away with these trades and do it yourself it will be invaluable. 

It may seem like a lot of money but you can sell it on afterwards

mine comes out nearly every week for some job or another. 

 

Ps. Don’t put stakes in your concrete, it always looks rather amateurish, walking around with your receiver will make you feel like your a pro. 

[epsilonGreedy]

3 hours ago, Russell griffiths said:

If you are building a lot of this yourself

i would go and get a rotating laser and receiver 

most of the trades you employ will have one with them, so if you are going to do away with these trades and do it yourself it will be invaluable. 

 

 

I am beginning to think I need one of these, is £500 to £700 the going rate for something decent?

 

3 hours ago, Russell griffiths said:

It may seem like a lot of money but you can sell it on afterwards

mine comes out nearly every week for some job or another. 

 

 

I am trying to create a list of tasks for a rotating laser to justify the purchase:

1. Translate official OS height to reference marker within my plot.
2. Establish height differential across foundation plan.
3. Check level of scraped back soil plinth.
4. Check trench depth across foundation plan.
5. Measure height of concrete pour to obtain mm accuracy of trenchfill height across foundation plan.
6. Guide further fine tuning of below dpc plinth level as courses are laid.
7. Check levels as block and beam floor is laid.
8. Measure gradient of drainage trench falls.
9. Check internal block course levels as above dpc elevations are built.
10. Measure levels prior to fitting first floor joists.
11. Check window/door aperture levels and squareness as brick/blocks are laid. 
12. Post weather tight, help vertical/horizontal aliment of stud walls, plasterboard panels, kitchen units.

What have I missed?

 

[MikeSharp01]

Pretty comprehensive list but you can also use it to set up your string lines for brick / block work and such. I fitted my reciever to the digger arm for grading the site it was fine providedicated the digger was always facing the laser device and you only get +/- 50mm on the reciever.  I have one of these and it has been well worth it - I didn't get it from this supplier though.

[Mr Punter]

I think you need:

 

Rotating laser level - ground works, foundations, concrete, brickwork

 

Laser line level - tiling, kitchen fitting, flooring

 

Long spirit level - wall and floor level and plumb

 

Short spirit level - sockets and switches

[epsilonGreedy]

16 minutes ago, MikeSharp01 said:

I fitted my reciever to the digger arm for grading the site it was fine provided the digger was always facing the laser device and you only get +/- 50mm on the reciever.

 

 

Hmm that is disappointing for a £600 piece of kit, my home made water spirit level was good for a 20mm accuracy across 10 meters. Is it more accurate when not attached to the digger arm?

 

 

[epsilonGreedy]

20 minutes ago, Mr Punter said:

Rotating laser level - ground works, foundations, concrete, brickwork

 

Laser line level - tiling, kitchen fitting, flooring

 

 

I did wonder after posting if using a precious £600 rotating laser for internal 1st / 2nd fix jobs was a bad idea. Laser line levels are a quarter of the price, looks like I need two decent lasers.

[Declan52]

Hire a rotating level for your founds.

Use it first to figure out how much needs stripped of from transfering a level from an outside marker like a kerb, manhole cover. 

Dig out whatever needs removed and dig the trenches.

Put some wooden stakes in your trench for a concrete depth height. One at each corner and a few along the long walls. Tap these in and set them all level.

The next day after your concrete is poured go round and see what way the corners are. Might be +-20mm which is no big amount. 

Next height will be your blocks that the b&b floor sit on. By going round the concrete you will know which corners are low/high and  then using a tape the brickies will be able to bed up/down to get to whatever height you need to be. 

Put a masonry nail in the top course of block in each corner set level. From this nail it's easy to use a tape to check you are building it level the whole way up. Don't be afraid to put a tape on each corner during the build and if it's out ask why.

If it's brought up level then your window cills,wallplate etc will all be level. Any brick layer worth his salt will have profiles at the corners so will be easy to maintain the correct bed depth from the bottom to the top.

If you really want a level don't discount an optical level. Only thing is you need another pair of hands, but they can be had for less than £200.

A long level and a line laser is all you will need for the internal work.

[Russell griffiths]

If you get a good level it should have a setting to alter your accuracy 

 

for instance @MikeSharp01 said he had it set on his digger arm, so he probably backed of the accuracy as 50 mm in a footing is good enough. 

 

Mine has two settings rough and accurate 

on rough I can still get within 5mm over 20m

on accurate it can be a bit finicky as you start splitting hairs over the thickness of a string line. 

 

If you can get one without a staff I would, I never use mine instead get a nice smooth piece of 2x2 and paint it white so it is easy to see all your little pencil marks on it. 

[MikeSharp01]

1 hour ago, epsilonGreedy said:

Hmm that is disappointing for a £600 piece of kit, my home made water spirit level was good

Sorry for rhe confusion. The accuracy is 0.5mm (half a mm)  but the range the reciever can read either side of the rotating laser line is 50mm so the digger  bucket  has to be within 50mm of the line to get a reading it does tell you if the last reading was above or below the line if it can't any longer see it so you know which way to go. I found it worked OK once you got the hang of it. The 0.5mm measurement is great for everyday work. And getting a reading either side I'd fine. Our foundations has to be +/- 10mm. You can of course measure any height by skinning the reciever up the staff and adding the staff reading to the scanner reading.

 

Edited June 14, 2018 by MikeSharp01

[SteamyTea]

On 13/06/2018 at 13:49, PeterW said:

Or look here Bench Mark database

What a brilliant tool.

[Tyke2]

Hi

 

The old fashioned way works ok too!.

 

This video shows setting out in plan form only, but it shows how to set the profiles too.

https://www.youtube.com/watch?v=7dN3Iku0Bns

If you set the string to a known level. Say 500mm above DPC. then work out the distance from this level to the required bottom of foundation. Make a stick this long - this is your "traveller" the digger driver then uses the stick at each point along the string for his depth. Similar to this method for digging a trench:-

http://www.ruralworks.com/reports/profileboard/ProfileBoard.html

 

Costs are some bits of wood, and a ball of string. This method would be used for most buildings before laser levels were invented.

Edited September 5, 2018 by Tyke2