Strip foundations

H

hayabusa

Registered User
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115
Folks,
I am getting strip foundations put in , in the next few weeks.
I do have an engineer to oversee all, however i would like to know for myself a few of the steps as I am a little confused.
Firestly let me explain, this will be strip with fill and a concrete slab poured. Then after the house is roofed there will be 100mm kinspan insulation and a 75 mm screed over this.

However my concern is that there are quite a few walls to build on the gnd floor, and these will be solid block walls.

Is it correct that all rising walls will be built to a certain level, and each space filled with compacted hardcore, then sand blinding and then DPM and radon layer, then concrete poured over this.
If this is the case then, how does one know where to continue the wall from. I do know that the measurements should point out wher the rising walls are.

Or is DPM put in in each room up to the rising wall.
Difficult for me to explain.

Any input on the process would be appreciated.
 
Re: Strip Foundations.

When doing a rising wall, the internal walls have to be built and are normally kept down 9 inches below the external wall so that the interior is all one level.Dpm is then rolled out, overlappiing the external block and tthe internal walls are then built up to the same level so as to screed off.This is just one way of doing it.
 
Re: Strip Foundations.

as csmd states...
its a better standard of workmanship to leave the internal rising walls 1 block course below the outer walls...
this means the whole floor can be poured as one and the internal walls act as support to it....
otherwise you will end up with many seperate floor slabs which may settle differently...
 
Re: Strip Foundations.

Hi sydthebeat,
I'm in a similar situation. Do I lay the insulation between the rising walls in each room before pouring the screed or do I fill up to the level of the rising walls with compacted hardcore, then lay insulation above the rising walls so to speak? May sound rather uneducated, but if the insulation is above the rising walls, is there any issue wrt carrying the "load" or supporting the screed? One other quick question (since you sound knowledgeable on the subject), can you lay insulation directly over hardcore, then screed on top or do I need to pour a subfloor over the compacted hardcode? Thanks in advance, apple1
 
Re: Strip Foundations.

a couple of questions there apple1..

1. the insulation is laid on top of the waterproof element (the 1200 gauge Damp Proof membrane)... this membrane can be punctured by the hardcore, therefore the hardcore is generally 'blinded' with sand to prevent these punctures.... with this situation the floor slab can be poured as 1 pour of 150mm and powerfloated after.

2. The insulation is generally stopped at the inner rising walls, and the dpm is carried up and over them at this point. And before you ask, yes, this creates a cold bridge at this point... but either method would create a cold bridge.... The other method of carrying up the inner rising walls and pouring each room floor slabs seperately has the advantage of having a level that you can screed off ie the top of the block, but the disavantage is the likelyhood of having slightly different floor levels, and an increased chance of a sunken floor slab. And remember to reinforce over the rising wall in the floor slab.. this detail is on page 43 of the HOMEBOND house builders manual (The Bible!!!!)
 
Re: Strip Foundations.

Just a tip, If your pouring the slab in one go. Put in a couple of nails in the side of your external rising walls either side of your internal rising walls. This will save your time when setting out internal walls from the floor slab up.
 
Re: Strip Foundations.

Thanks Syd. Appreciate very much the insight. If I follow you correctly then, what I should do is as follows:
1. Fill inside my rising walls with compacted hardcore, leaving it 65mm below the internal rising walls (to allow for 65mm insulation).
2. Cover with DPM/radon barrier
3. Place my insulation in place so that the top of it is flush with the internal rising walls.
4. Lay my UFH in the loops as prescribed.
5. Pour the concrete to a depth of 6" & power float.

This option negates the need for a concrete subfloor.

One quick one before I go.....without buying the manual, how do I re-inforce the 4" section above my inner rising walls? Thanks in advance, apple1
 
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