Insulating/strengthening single skin outhouse

[Grahamshed]

Title says it all really, we have an 'outhouse' for want of a better word over the side door to the house proper. It is single skin brick with tiled pent roof. The whole structure is maybe 9ft by 7 ft with a door in each end. The brickwork needs repointing and 'brick bees' are eating small holes right through the bricks.
I want to insulate the walls and strengthen them without loosing any space which means doing it on the outside....... any ideas folks ?

 

[SteveF]

battons
celotex
vapour barrier
aquapanel
render
paint

job done

Steve

 

[Grahamshed]

Okay ..... good with all that till you got to aqua panel..... which is ?

 

[SteveF]

concrete water resistant plasterboard sort of stuff

normally used for bathrooms ...but why not

Steve

 

[MMUK]

Aquapanel is basically a cement board used on exterior studs to take render when you clad the existing wall. An exteroior equivalent to plasterboard HTH

 

[carlb40]

You can render directly onto celotex etc and use a re-enforcing mesh. Plus you can fix the celotex directly to walls.

http://www.ebay.co.uk/bhp/insulation-fixings

 

[Grahamshed]

OK, have to check on that. Would all that go right down to the ground ( mostly slabs/concrete ) or should I make a kind of concrete foundation alongside the existing one ?

 

[flat n smooth]

a way u could do this is with an ewi (external wall insulation) system.
this would mean fixing insulation boards on the outside of the walls which are then base coated with a mesh sunk into it
Then a choice of top coat can be applied to suit the existing finish on the property
This system would not take up any of the internal space

 

[Drudgeon]

The advantage of battening first is you can pack the battens off top and bottom by a small amount and you have a cavity/void which will aid insulation, you could clad the battens in some form of ship lap, timber, UPVC etc etc rather than rendering, would probably save on cost.

 

[Bigdanny]

Carls method is good. Is used widely here in Bulgaria with XPS stuck on with adhesive and plastic rawlplug nails, similar to tile adhesive but usually has flex in it, then skimmed with nylon mesh and external finish render. Works well down to -25C here.

Danny

 

[Drudgeon]

OK, have to check on that. Would all that go right down to the ground ( mostly slabs/concrete ) or should I make a kind of concrete foundation alongside the existing one ?

I would say if you were to use a visqueen type moisture barrier, tack to the wall (externally) a foot up, then batten/insulate over the top, you could then wrap this back up the front ensuring at least the bottom 12" or so is protected. Not a standard detail but a means of getting over a problem I guess.

 

[carlb40]

Carls method is good. Is used widely here in Bulgaria with XPS stuck on with adhesive and plastic rawlplug nails, similar to tile adhesive but usually has flex in it, then skimmed with nylon mesh and external finish render. Works well down to -25C here.

Danny

I was on a job last year in Banbury and the housing association used that system. Along with a pre coloured water based render type system.

 

[blackrodd]

Can I suggest an alternative? It Seems a lot of work and expense to save the 50mm lost around inside by tanking out with synthaproof, or similarand dry lining with 38mm thermal plaster board, then tape and jointed. all the work is inside, as well!
Cellotex and the materials spoken about are all good but very expensive.
It would probably be a good idea to work out a square metre costing.
38mm thermal board @2.88 square mtrs should be around £8. mtr square and I would guess the synthaproof, adhesive and jointing stuff at around another £5. mtr. HTH Regards Rodders

 

[MMUK]

.
38mm thermal board @2.88 square mtrs should be around £8. mtr square

I take it you mean plasterboard with polystyrene backing?

Selco charge £22 for an 8x4 sheet. I've started buying it from Magnet for £15 a sheet inc VAT.

A much cheaper option though is to buy an 8x4 3/8" plasterboard for £6 and a sheet of 25mm polystyrene for about £5. Just not practical for me on these roof conversions.

 

[blackrodd]

.
38mm thermal board @2.88 square mtrs should be around £8. mtr square

I take it you mean plasterboard with polystyrene backing?

Selco charge £22 for an 8x4 sheet. I've started buying it from Magnet for £15 a sheet inc VAT.

A much cheaper option though is to buy an 8x4 3/8" plasterboard for £6 and a sheet of 25mm polystyrene for about £5. Just not practical for me on these roof conversions.

Yes, thanks for pointing out thermal plasterboard was my meaning, another senior moment! Regards Rodders

 

[lincs1963]

OK, have to check on that. Would all that go right down to the ground ( mostly slabs/concrete ) or should I make a kind of concrete foundation alongside the existing one ?

I would say if you were to use a visqueen type moisture barrier, tack to the wall (externally) a foot up, then batten/insulate over the top, you could then wrap this back up the front ensuring at least the bottom 12" or so is protected. Not a standard detail but a means of getting over a problem I guess.

Not a very good idea, you are effectively creating an internal 'gutter', any condensation or moisture that forms within the wall will not be able to escape. Apologies if I am misunderstanding your suggestion.
I would certainly be looking at doing this job internally, you could create yourself all kinds of problems with regards to finishing at the eaves and gable verges.
HTH, regards, Neil

 

[MMUK]

If you're set on cladding the outside I'd personally not clad below the damp course. You can close off the bottom edge with a plastic trim and use a bell cast rendering bead to create a bottom edge for the render. You will need to fit a lathe to fix the render bead to though, I'd fit a treated 2x2 around the bottom perimeter if you're using 50mm Celotex, then fix the stop bead to this and use a 60mm uPVC window trim to cloak off the underside but don't silicone seal to the brickwork (to allow any moisture between bricks and Celotex to weep out).

 

[Hivenhoe]

Some advise here http://www.energysavingtrust.org.uk...-insulation/Choosing-external-wall-insulation

Local authorities around here's been doing it for about a year or so.
Jury's out, as the firm they've had doing it, covered up vents, didn't remove some pipe work so you have channels ( cold spots) left gutters open so water now runs down behind join. Someone either got a backhander and certainly deserves one!
The house/porch will still need to breath out moisture, so allow for some sort of top and bottom ventilation but this sort of defeats the insulation?

On Radio 4 now or iPlayer later?

 

[Grahamshed]

Thanks for your input guys. Plenty to think about there. I am loath to take any of the inside space ( it could really do with enlarging ) but what to do with the outside skinning at the top of the long (non eaves ) side is a problem

 

[MMUK]

Gable ends? You could try fixing a 2x2 batten at the top and then cloaking with 100x80 plastic angle like this stuff.

About £20 for a 5m length from Eurocell Fix it down with screws and cup/caps.