When to do pad foot

[LA3222]

I have a couple of pad feet which will sit in the hardcore layer under my insulated slab, I'm just trying to work out when to do them.

 

Would it be best to shutter them from the off and build up the hard-core/sand layers around them or get the hard-core base laid and then dig out the area for the padstones?

 

I understand that pathways for foul runs are dug out after so wondered if to do the padstones then too?

[LA3222]

No takers?

 

Well unless someone says otherwise I think that the easy option is to get the stone in and level and then dig out where the pad foot needs to go.  I will then shutter the pad foot for the concrete, once it has gone off remove the shuttering and tidy up/level the stone into any gaps around the padfoot.  I assume two days will be enough time to leave the shuttering in position - I dare say 24hrs will suffice?

[Russell griffiths]

Ok I will chuck this in, why are they not connected to the slab ?

why not dig out the shape, line it with the insulation board as shuttering and pour at the same time as the slab. 

[LA3222]

Ha @Russell griffiths I appreciate the bite ?  They are under the EPS to support a high point load.  I then have to insert 2 layers of 3 x foam perinsul blocks to support said point loads in lieu of the EPS.

 

It seems a straightforward thing to do, just firming up in my mind what the most efficient order to do it all would be I.e. cast the pad then lay the agg or lay the ahh then dig out/cast the pad. 

 

As they say, picture paints a thousand words:

 

 

[Russell griffiths]

If your happy doing all that yourself, I don’t think you need to ask much. 

Crack on bud 

just out of interest what is the high load area holding up. 

[LA3222]

There are three areas - two are steel posts and the other is just an area where the point loads have worked out high for whatever reason.

[SuperJohnG]

@LA3222 typical....I was searching for this very thing and you'd already done the asking for me. What did you end up doing? 

 

I have three of these pads from tanners too. But of a pisser really, I wasn't expecting them and seems to have added complexity (and costs). 

 

I'm now back challenging the superstructure engineer on his points loads. He seems to think I have 34 Tonnes of point load from a roof on a single story vaulted area only 7m x 8m. Doesn't add up to me..

[LA3222]

@SuperJohnG in the end I made some boxes up to size out of ply and put them in first. I screwed some stakes to the corners of them so could hammer them into the ground and use them to bring the boxes to the correct level. One they were at the right level I braced them internally so that as I whacked the stone around them it didn't cause the sides to bulge inwards.

 

The biggest challenge was getting them in the right place. If you get some profiles set up it should be fairly straightforward for you. I took view that the pads are massive and there is likely some tolerance involved with regards to getting them exactly right so I got them within about 20mm which I felt was fine. 

 

I got the concrete into them one the pad was done as the lorry could drive right up to each box. A vibrating poker, a tamping stick and 0 mins later job done. I left the ply box in place.

 

When I cut down through the insulation it was rather satisfying to see they were where I expected. Cutting down through 200mm of EPS 300 was hard going.  I used one of those folding tree branch saws fir most of it. I made up a mortar mix, put a bed down, first layer of foamglass in  another bed of mortar and put top layer in flush with the insulation. Any gaps around them from rough cutting I filled with foam.

 

I'll add pictures once I'm on laptop.

 

 

Edited November 13, 2020 by LA3222

[Big Jimbo]

That looks great, but what a pain in the butt to have had to do them.

[joe90]

Your not using child labour are you ???

[Onoff]

5 minutes ago, joe90 said:

Your not using child labour are you ???

 

Guess who's getting RoughNeck tools for Christmas!

[SuperJohnG]

4 hours ago, LA3222 said:

@SuperJohnG in the end I made some boxes up to size out of ply and put them in first. I screwed some stakes to the corners of them so could hammer them into the ground and use them to bring the boxes to the correct level. One they were at the right level I braced them internally so that as I whacked the stone around them it didn't cause the sides to bulge inwards.

 

The biggest challenge was getting them in the right place. If you get some profiles set up it should be fairly straightforward for you. I took view that the pads are massive and there is likely some tolerance involved with regards to getting them exactly right so I got them within about 20mm which I felt was fine. 

 

I got the concrete into them one the pad was done as the lorry could drive right up to each box. A vibrating poker, a tamping stick and 0 mins later job done. I left the ply box in place.

 

When I cut down through the insulation it was rather satisfying to see they were where I expected. Cutting down through 200mm of EPS 300 was hard going.  I used one of those folding tree branch saws fir most of it. I made up a mortar mix, put a bed down, first layer of foamglass in  another bed of mortar and put top layer in flush with the insulation. Any gaps around them from rough cutting I filled with foam.

 

I'll add pictures once I'm on laptop.

 

 

 

 

@LA3222 that's great thanks for those and very helpful to understand more. I wasn't expecting to having to add these and its just added an extra step of complexity for the groundworks. Albeit - I have now went back to my superstructure engineer this morning and told them to send me the calcs for point loads, I seem to hace excessive load (in my opinion) and I think they have added some fat into the dead loads causing it to be overengineered, hence working back and forth with Tom and tanners to try and make it more realistic and lose some of them if possible.

 

 

Also really helpful to see pics of ducts in there too. 

Edited November 13, 2020 by SuperJohnG

[LA3222]

Got to put the kids to work every now and then?

 

@SuperJohnG putting the ducts in was another PITA because I was worried I'd bring them up in the wrong place. If I'd got it wrong by 20/30mm they'd have been in the wall. As it is I'm not overly chuffed with where the water pipes are and its mainly a consequence of not having a fully planned out plant room. They are right next to where the UFH manifold now resides so I need to stick a 90 bend on it to bring it away and give me some working space. I still don't have my plant room planned out yet and MVHR is on my to do list soon.

 

With the foul drainage, once the pad was all flattened I got the digger driver to nibble out a channel where they all needed to be.  My biggest stress point with all of this stage was whether things would turn out to come up the slab in the right place. I was pretty much bob on for the most part but it was a worry throughout.

 

I'll stick some pics on later of the drainage going in etc. 

[LA3222]

Drainage going in and sand blinding layer that followed. @SuperJohnG the sand blinding needs to be done to a tight tolerance otherwise the kore blocks just won't sit well against each other and you get gaps of a couple of mm between them, over an 18m run this soon added up so I had to take it all off and redo the sand. Much better second time around!

 

Forgot to mention before, I hammered a wooden post in the ground to tie the ducts to so that as the stone went down they remained vertical. Be careful on your bend radius as they come through the slab, my electric duct caused me issues. I have a 5core 25mm2 cable in a 90mm duct, as I pulled the cable in it wouldn't follow the bend and just pulled into the sidewall of the duct. Tantalisingly close but I couldn't get a hand onto it, in the end I had to pull it all out and feed it out from the house end, other than a couple of wasted hours not a major drama but it could have been!

 

 

 

 

Edited November 13, 2020 by LA3222

[Gus Potter]

Hi all.

 

This may seem like music to some ears... £££ savings possible here.

 

Key points for pad footings, and any footings for that matter are to:

 

1/ Put them in the right place and at the right depth. Remember that deeper is not always better, sometimes we look to sit the footings on a hard crust rather than digging for glory. The hard crust spreads the load out so when it get to the softer lower area it does not load that softer layer so much and this reduces settlement amongst other things.

 

2/ It's actually better to have rough sides to the founds in virgin ground as the concrete gets into the vertical sides and provides a extra shear key, thus spreading load more. So have a think about that before you spend money and time on shuttering, maybe just spend a little more on concrete, it's worth weighing it up.

 

3/ Do not put services etc under foundation pads as you can compromise the design.

 

4/ Please remember that excavations can be dangerous and behave in unexpected ways.

 

5/ 34 tonnes is about 340 kN which is a lot for a single storey small span building unless you have some heavy masonry? 100 kg ~= 1 kN... 1 tonne ~= 10 kN...

 

6/ Oh, and as a teaser for the basement folk.. you often design for minimum surcharge load on the finished ground around the outside of the building of 10 kN/ sq metre ~ 1 tonne a sq metre. This is to account for someone driving a JCB etc around the building later, or someone changing the ground level, storing material. Sometimes this can drive the design even if you have a low water table, favourable ground and so on.

 

In summary, it's worth having a chat with your Engineer. Pad footings can also resist horizontal loading so it's important to understand what the are intended to do. Are they for just carrying vertical load or do they also need to take some sideways loading.. often this happens when you have a "goal post" portal frame type of structure or the pads are designed to resist the overall sideways wind load on the building.

 

 

 

 

 

 

[SuperJohnG]

8 hours ago, LA3222 said:

Its mainly a consequence of not having a fully planned out plant room

 This helps move me along. I've written all my ducts down and been avoiding eating that frog of planning them all out in my plant room. I have a good idea of where it is all going but just need to finalise in ACAD. Also gives me the stress as I want them exact and planning how I achieve that with surveyor and controlling the location without it costing a fortune. I have a local guy who is good and has some good ideas around the profile boards and he is genuinely interested so hopefully I can get them all bang on. Would break my heart I think coming up in a wall. 

1 hour ago, LA3222 said:

otherwise the kore blocks just won't sit well against each other and you get gaps of a couple of mm between them,

This is a great wee titi bit of info. 

 

As always I appreciate you taking the time to post these @LA3222 it will help no end. 

58 minutes ago, Gus Potter said:

 

5/ 34 tonnes is about 340 kN which is a lot for a single storey small span building unless you have some heavy masonry? 100 kg ~= 1 kN... 1 tonne ~= 10 kN...

 

 

Fortunately for me I'm a chartered mechanical engineer..albeit my structural calculations are usually moving up  down and left and right as I design equipment for offshore. So that all make sense. 

 

Had a long chat with the engineer this morning...loads now revised and significantly reduced to where they should be, its now engineered to suit rather than over engineered. I'm hoping Tanners might get rid of a few pads once they see the revised point and line loads. 

[Gus Potter]

Spot on @SuperJohnG it's always worth phonig up for a chat and asking for an explanation.

 

For all it may be worth having a look about for Engineers who are local to you that can provide a similar service in case you encounter a soil / ground works problem. In this case if you have to have a few site visits then any initial savings may be lost? Also.. what is the cost of supervision. Often a local Engineer will just "drop in" to see how things are going! It's amazing how that can inprove the quality of the work.

 

 

[LA3222]

"Would break my heart I think coming up in a wall." Its an achievable task without a doubt, check and double check your measurements and it will work out. Mine ended up exactly where intended, my grievance with the water pipe location stems from my failure to come up with a comprehensive plan of how I intend to install all the equipment in the plant room rather than getting the location wrong.

[SuperJohnG]

Great pics @LA3222

 

How thick was you slab by the way?

 

Tanners had called saying the super structure changes now added another 2 pads (5 in total now) however they have told me they can increase the slab by 50mm (so from 100 up to 150mm non load bearing and 200-250mm in the ring beam) which will  remove the need for the pads. 

 

Only downside I can see is extra concrete ( I calculate around extra 9 cubes, which is a 40% increase) an extra 1k i think but drastically simplifies it again. I can't see any other reasons not to? anything I should consider? 

[Oz07]

If take the grand extra with simplification if it were me. Messing about with the boxes plus cost of concrete inside of them would put me off. 

Good pics @LA3222. Look like you had decent depth to work with on your drains!

[LA3222]

1 hour ago, SuperJohnG said:

Great pics @LA3222

 

How thick was you slab by the way?

 

Tanners had called saying the super structure changes now added another 2 pads (5 in total now) however they have told me they can increase the slab by 50mm (so from 100 up to 150mm non load bearing and 200-250mm in the ring beam) which will  remove the need for the pads. 

 

Only downside I can see is extra concrete ( I calculate around extra 9 cubes, which is a 40% increase) an extra 1k i think but drastically simplifies it again. I can't see any other reasons not to? anything I should consider? 

What will that do to your kore quote? Simplifying sounds good, if I'd thought about it I'd have been happy to up spec the slab vs mess around with pads.

[LA3222]

25 minutes ago, Oz07 said:

If take the grand extra with simplification if it were me. Messing about with the boxes plus cost of concrete inside of them would put me off. 

Good pics @LA3222. Look like you had decent depth to work with on your drains!

Yeah, I had to tap into the main sewer just outside the drive at 3m depth. It was a 60m run to the house but falls were easy to sort out. 

 

Whilst mentioning falls, @SuperJohnG the better Lazer levels have a function on them which allows you to input the required fall into it. Once the staff is set you can then just walk down the drain run and measure away without having to change/recalibrate anything else. Makes life so bloody easy when getting the falls its unreal!

[SuperJohnG]

1 hour ago, LA3222 said:

What will that do to your kore quote? Simplifying sounds good, if I'd thought about it I'd have been happy to up spec the slab vs mess around with pads.

Hm. Thats maybe one to check in the morning with Kore actually. I'm assuming that having a thicker slab is a better thing somewhere..maybe better for the UFH. 

1 hour ago, LA3222 said:

Whilst mentioning falls, @SuperJohnG the better Lazer levels have a function on them which allows you to input the required fall into it. Once the staff is set you can then just walk down the drain run and measure away without having to change/recalibrate anything else. Makes life so bloody easy when getting the falls its unreal

Spot on thanks. Amy recommendations and ill have a wee read up? 

[LA3222]

10 minutes ago, SuperJohnG said:

Hm. Thats maybe one to check in the morning with Kore actually. I'm assuming that having a thicker slab is a better thing somewhere..maybe better for the UFH. 

Spot on thanks. Amy recommendations and ill have a wee read up? 

I'd agree more concrete is better, it will change the profile of the EPS insulation pieces though as the perimeter upstand will need to be 50mm higher?, which may affect pricing. If its feasible then I'd say do away with the pads, it will make things easier for you.

 

Not sure what model it was, the neighbour is a builder and it was his. A variant of the Leica Rugby family, I expect most of the more expensive types do this, it just wasn't something i had considered until the neighbour set it up. A doddle to set up and a boon to use.

Edited November 16, 2020 by LA3222

[SuperJohnG]

6 minutes ago, LA3222 said:

I'd agree more concrete is better, it will change the profile of the EPS insulation pieces though as the perimeter upstand will need to be 50mm higher?, which may affect pricing. If its feasible then I'd say do away with the pads, it will make things easier for you.

 

Not sure what model it was, the neighbour is a builder and it was his. A variant of the Leica Rugby family, I expect most of the more expensive types do this, it just wasn't something i had considered until the neighbour set it up. A doddle to set up and a boon to use.

I was thinking that now and yep, that height will go up which will mean the wall thickness of that section will increase, so cost will rise there. Also wondering now I'll think the TYPE 3 stone underneath will increase from 150mm to 250mm probably. so possibly 2-4k extra depending on the Kore costs.  I'll maybe check a few things in the morning with Tanners, at 2k it makes it simpler for sure, but at 4k it starts to not make sense, considering the concrete for the pads only costs 150 quid. The rest is just time to dig the holes out really, plus the foamglass blocks.