new member - new summerhouse project

[julesm]

hi everyone

 

I have joined the forum in the hope that you erudite folk can help a hapless diy'er/consumer help make some informed decisions on material choices.

instead i have jumped feet first into a garden structure - thinking it was the way forward.

 

i purchased a light gauge steel frame that is sat on ground screws - this was due to an undulating lawn and a some pretty big tree stumps and roots that wouldn't have allowed a base

 

so my first problem is - how am i going to insulate the floor on this damn thing -  as due to its construction,, i cannot get any PIR boards to get a tension fit , i cant get any mesh underneath to prevent rockwool from falling out due to the brackets that it sits on.

 

my uncle said as i will not be in it 24/7 - there is no need to bother ??

 

any ideas or suggestions please 

 

many thanks in advance and apologies for such daftness

[SteamyTea]

Welcome

 

An interesting problem as you have already erected the frame.

Will you loose too much height in the shed if you put 100mm of foam sheet on top of the frame?

 

A bit of a left field idea would be to pull some plastic sheet under the structure, then pour in two part expanding PU foam.

[Bonner]

Depends what it will be used for and when? How do you intend to insulate the walls and roof? Have you got space to put some PIR over the frame? Even 25mm would be better than nothing. Although you have a cold bridge with the steel, it’s still worth putting 50mm PIR in the frame if you have the time. Cut it a big bigger and stick in with expanding foam.

[julesm]

many thanks for the responses thus far

this is something i am considering i coming up off the floor with battens and then jamming pir into them 

 

for the walls - i intend it to use a breather membrane on the external and just use mineralwool to try and contain costs.

 

daft question ( prepares to be lambasted) could i not supefoil the floor and board over it ?

[Radian]

I doubt if you would need to batten the floor. Just lay rigid PIR straight over and top with ply or flooring chipboard. The load is spread over the large contact areas. Even just 50mm would make a big difference. Might want to do something to prevent vermin chewing into it from below though? Superfoil not much use especially if squashed flat.

[Gone West]

If possible I would board the outside of the whole frame including under the floor and fill with Frametherm. I would put a thin layer of Celotex over the whole of the inside of the frame and board over.

[Big Jimbo]

You will have spent a few bob on that. It looks like it is within P.D. 30sq m limit. personally, i would clad the outside with 50mm pir. It looks like you would have room re the roof overhang. I would put 50mm on the floor, and board over. Don't skimp now. That structure is going to be there for years.

[julesm]

6 minutes ago, Gone West said:

If possible I would board the outside of the whole frame including under the floor and fill with Frametherm. I would put a thin layer of Celotex over the whole of the inside of the frame and board over.

thanks i cant get access to under the floor 

let me investigate the frametherm 

[ProDave]

Re the floor.  Drop wood into the bottom of the frame void so it sits on the bottom of the C section frame members.  It will be a tedious job as you won't be able to do it in once piece per void, it will be separate bits cut so you can slot them in and slide them into place to drop down.  Once you have that you have support to full fill the void with frametherm.  Sheet over the top of all that with PIR as well if you want more insulation.

 

Don't leave any gaps in the support timber, you don't want vermin to get in.

[ToughButterCup]

5 hours ago, julesm said:

..

my uncle said as i will not be in it 24/7 - there is no need to bother ??

...

 

He's wrong.

I'll leave the technical bits (of how to achieve it)  to others, but I suggest that you should consider the need for your building to be as unreactive to temperature change as possible.

 

Slow to heat up and just as slow to cool down.

(Called a 'U Value'  if you want to research further)

[Gone West]

4 hours ago, julesm said:

thanks i cant get access to under the floor 

Is it impossible to unbolt it from the ground anchors and jack up one end to be able to slide a board under and screw down through the frame flange.

[julesm]

i think lifting it is prob out of consideration

i contacted a steel gauge installer and they have said cut PIR and use expanding foam?

[julesm]

next question - i dont have any decent array of power tools 

so will be hiring 

 

i have seen various youtube videos of people with high powered ( ballistic) nailers screwing drywall straight into steel

 

similarly could i use a ballistic nail gun to go straight into steel with the p5 flooring

 

many thanks

[Gone West]

3 minutes ago, julesm said:

i contacted a steel gauge installer and they have said cut PIR and use expanding foam

Are you going to use wire mesh under the floor to protect the insulation from the rodents.

[julesm]

i reckon so - if i can get a good purchase 

are there any other alternative measures i can take for rodent protection?

[SteamyTea]

I don't think doing this job well will be that hard.

Get yourself a half decent cordless drill from Screwfix, or Lidl even. You will need one anyway.

If you are adamant that you cannot get under the base frame at all, then you will have to 'work from the top'. 

You can make templates from cardboard for any rodent proof mesh (you will need to buy some tin snips) and then place them in each void, attaching to the frame with a decent adhesive (CT1 maybe).

Them fill with just about any insulation type to the top of the frame. Then a 12mm flooring board, then 50 to 70mm rigid PIR or PU insulation sheet board, then 18mm flooring sheet.

This may seem over the top, but heat loss through the floor gan be quite large.

You will also need to fill up the perimeter gap between the frame and the ground to stop air movement. Though I suspect you will need a bit of ventilation as the ground will be damp for many years.

 

Or just pour in 2 part expanding foam.

 

https://www.cfsnet.co.uk/acatalog/CFS_Catalogue__2_Part_Polyurethane_Foam_Liquid_415.html

 

[Radian]

6 minutes ago, SteamyTea said:

Or just pour in 2 part expanding foam

That's what I was wondering about. Back in 1980 something I bought some 5L containers of a two part product that mixed in equal quantities expanded by 100 fold. Used it everywhere (not always intentionally). I guess it was Polyurethane. Put up some formwork around the outside and fill the whole base.

[SteamyTea]

1 minute ago, Radian said:

Used it everywhere (not always intentionally)

Used to make tooling to mould PU. The factory used to squirt it every where. If you think a tin of squirty foam is uncontrolled, watch an idiot with a proper industrial injection matching with shot weights of 7 or 8 kg. Fantastic mess.