Summer House base help! Packers or re-skim the concrete

[James 2 Sheds]

Apologies for the bullet points (this is just to try and keep it to the point) and thanks for any help/ suggestions in advance.

• We have just bought a summer house (10 x 12)
• We have laid a raised concrete base.
• We thought it was level but when they arrived to assemble it, it was out. They supply a wooden base to let the air flow. It comes in three parts and couldn't be screwed together because the base was out, so we need to rectify.
• A family friend has said that this can be done with plastic packers. He has levelled of the air flow base (I don't know the correct name!) using these but it does mean that quite a lot of the wooden struts (again don't know the technical term! - they run the length of the base) aren't now touching the concrete.
• Is this a good idea? The concrete base was only slightly out but now using the packers to level off the base that they are going to place the summer house on to, has meant a lot of wood is not touching. Does this put more pressure on the packers? I understand that they can take tons of weight.

If any one has any helpful comments they would be greatly received!

 

[JohnD]

The concrete base was only slightly out

How slight?

Can rain fall on the base?

When was the base poured?

Photos might be helpful

Do you know anyone who can lay bricks?

 

[James 2 Sheds]

Hi - Pics now attached.

A family friend has come round today to have a look. He's put packers under to make it level just to get an idea. As you can see this means that the wood is now raised. The first pic show a side view. The second is a front view. I have pushed the packers back so you can see the gap between concrete and wood. I think he has had to do this all the way round because the base was in three parts and in levelling the first this has cause the others to become raised when levelling all three and screwing them together.

The weight of the house means they're not going any where but I'm worried about extra pressure on those points. Would it make more sense to have more of the wood touching the concrete?

Rain will fall on the base. It was done two weeks ago. Mixed by hand, hence the uneven surface.

 

[JohnD]

Consider laying a bed of bricks, one course should do it, adjusting the depth of the mortar bed to achieve level. Mark the base to a stencil of the wooden frame so your bricks are a perfect fit. When firm, spread a thick layer of soft mortar over it, put down a DPM on top, place your wooden frame and tap it down, using a long spirit level, to ensure it is fully level all directions.

I think the base ought also to be fixed down to the concrete with some stainless bolts to prevent any movement.

The brick course and the DPC will prevent the timber getting wet and will resist dirt, leaves, water or animals getting underneath. You could use a few airbricks in the course too.

An easier but not so good option would be to squidge mortar under all the wooden bearers while they are held level by the spacers. When it is set, you can take out the spacers and squidge mortar in there too, tidy up the inner face of mortar and fill any gaps or hollows, and lay a DPC before putting the base back. It is best not to have the timber in contact with the concrete base, especially if rain can fall on it, as damp will travel into the timber and cause rot. Hence the DPC.