Foundation for a Garden Building

[ohnotagain70]

I am looking to install a 6m x 5m garden building at the bottom of my garden. It is of a SIPs construction with insulation etc. For foundations there is already a concrete base which is approx. 300mm deep approx. 9m x 7m so plenty of room for the building to be located on.

The issue is that these buildings usually sit on concrete piles with a timber sub base clear of the ground. In this case I need to ensure the timber sub base is clear of the concrete base. My idea would be to run a course of engineering bricks around the perimeter for the timber sole plates to be fixed to. The other alternative I thought of was to use concrete lintels.

I would be grateful if anyone is able offer some advice/experience of this situation. Additional insulation could also be laid in the void formed by this perimeter.

Thank you

 

[r896neo]

Your plan with the engineering bricks is sound. you can use them to build sleeper walls then lay your sole plates on a dpc on top of the walls

Is the building designed with a sip panel floor too? If your concrete base is truely sound you could add a dpm, insulation and a screed on top of that and form a traditional solid floor rather than have a vented sub floor void which may well become a warran for rats or other fauna?

 

[ohnotagain70]

Thank you for your reply.

This is one of the reasons why I wanted to utilise the existing base as we do have foxes etc.

I was hoping that the course of engineering bricks with the sole plates attached (a neoprene membrane is used between the bricks and timber) would then be enough to prevent vermin attack!

On the cost front, the timber sub frame is included. The cost of 30 sqm of screed may impact the budget a fair bit, but can always try to get a quote.

The building firm guy mentioned running the course of bricks and then pour self levelling compound within the perimeter to lay the insulation on. Should I lay a dpm first then add compound or would this not work very well?

Many Thanks

 

[r896neo]

I'm not sold on this idea of filling with insulation. was that their idea?

If the floor is designed to be a ventilated sub floor and you try and fill the void but dont do it perfectly then you run the risk of condensation and or problems in the longer term.

If the floor panel is already insulated then i would consider forgetting the insulation and ventilate it normally. Using clay air bricks rather than plastic should keep the beasts out.

 

[ohnotagain70]

Hi, got someone round for a 2nd opinion. Now have an option which is a mixture of the 2!!! To lay a reinforced concrete perimeter with DPC 6in high and then to lay insulation on DPC within perimeter and then screed the rest. Hopefully there will be a slight cost reduction in the building cost as a sub floor is no longer required and this could go towards the screed.

The only issue I have is that there is limited access to site

Thank you for the advice