100mm celotex as "hardcore" to raise patio base

[benjiman]

Hi,

I've got a solid concreted area as a patio. However the step down from the house to the outside is more than a foot.

I would like to raise the existing level. I know I can put down hardcore and compact before laying 4" on concrete as the final finish.

However I have loads of sheets of 100mm celotex left over from doing under floor heating inside the house.

When the UFH was done, 75mm of screed was put on top. I'm thinking is it possible to do the same thing outdoors? So use the insulation to raise the level and then concrete ontop? This would allow me to use up the spare boards rather than bring it loads of hardcore and compacter.

 

[oldbutnotdead]

I'm not sure how well Celotex etc will perform under a slab which is getting rained on. Theory sounds fine (it weirded me out when I first put Celotex under concrete- seems very wrong), cost-wise you might be better off sticking the Celotex on Ebay and using the proceeds to pay someone to do the hardcore, compacting etc (for 100mm in good nick you should get £20 per full sheet)

 

[Nige F]

If you're in E. Sussex I would buy some off you

 

[noseall]

Trade the Celotex for M.O.T. or concrete.

 

[^woody^]

It's so daft it just might work

 

[benjiman]

Cheers lads.

I know it sounds absurb, but just thought it might work considering it's done internally!

In regard to it being rained on, can easily put the jumbo roll I've still got left over of the DPM ontop of the insulation so no water gets to it.

Sorry not in E.Sussex. I may try a section and see how it compares to the area with hardcore. I guess the results will only be known after a good many years, but interesting to know how well it holds up over the years.

 

[freddiemercurystwin]

They can build roads on top of polystyrene.