Thermalite shield blocks for Garden Office

[Robert Taylor]

Hi,

We recently built a garden office under permitted development in our back garden using thermalite shield blocks. The blocks are very close to the fences around it about 20mm gaps all around. We realised later that the blocks haven't been rendered. Would this be a problem long term? Theres no space to do any rendering now as it is too close to the fences and none of the neighbours are prepared to give access by removing the fence panels. We have had it built for about 13 months so far. When it rains it does soak up the aerated blocks and then drys out. I have managed to put some concrete sealant (water repellant silicone) on the inside walls of the blocks only but only some areas before the plasterboards were installed. The main problem is the outside face of the office, those blocks currently have no protection. Should this be a problem? The inside walls have dot and dab plasterboards. Just normal 12.5mm thick plasterboards. Should this be a problem long term wise in terms of damp?

A few builders have given a few options but none consistent. Some have said remove the plasterboards and put fibre cement cladding and others have recommended installing OSB boards on the outside facing walls and securing with nails but others aren't convinced that this is doable as there isn't enough space to install these and recommended knocking everything down and starting again with solid dense blocks or bricks. Does anyone have any thoughts on this or is knocking everything down the only solution to avoiding damp and damage to the blocks? Some suggested spraying concrete sealant but others felt there is no space to do this.

Thanks.

Rob.

 

[Notch7]

Given the lack of access, your options are limited.

Maybe this would be doable:

1. fit 50mm x 25 mm battens, vertically from top, down to below height of fence, and full height at each end.

2. get a full 25m x 4m roll of black damp proof membrane, and cut it to size to cover garden office from fence down to ground.

3. fix a 50 x 25mm batten along the long side of the DPM

4. get the DPM in position and screw the long batten onto the bottom of the vertical battens you’ve fixed to the wall and allow the DPM to drape down - fix it at each onto the full height battens

5. add another row of vertical battens onto the original ones fitted, finishing 100mm below the batten holding the DPM to the wall

6. Fit some form of cladding across the vertical battens - could be timber, 12mm cement rendaboard of metal box section.


Your wall will now be protected from rain penetration.

if all the walls are single skin, it would be better if you covered it in Tyvek housewrap, fitted vertical battens, then clad it with something - rendaboard if you want a painted render finish.

I would avoid simply rendering a single skin wall - yes render is waterproof, but any cracks or entry points at openings will mean damp in the future.


If you had a builder make you a single skin garden office, you were badly advised.

 

[Jowwy]

Given the lack of access, your options are limited.

Maybe this would be doable:

1. fit 50mm x 25 mm battens, vertically from top, down to below height of fence, and full height at each end.

2. get a full 25m x 4m roll of black damp proof membrane, and cut it to size to cover garden office from fence down to ground.

3. fix a 50 x 25mm batten along the long side of the DPM

4. get the DPM in position and screw the long batten onto the bottom of the vertical battens you’ve fixed to the wall and allow the DPM to drape down - fix it at each onto the full height battens

5. add another row of vertical battens onto the original ones fitted, finishing 100mm below the batten holding the DPM to the wall

6. Fit some form of cladding across the vertical battens - could be timber, 12mm cement rendaboard of metal box section.


Your wall will now be protected from rain penetration.

if all the walls are single skin, it would be better if you covered it in Tyvek housewrap, fitted vertical battens, then clad it with something - rendaboard if you want a painted render finish.

I would avoid simply rendering a single skin wall - yes render is waterproof, but any cracks or entry points at openings will mean damp in the future.


If you had a builder make you a single skin garden office, you were badly advised.

They only have a 20mm gap……how can the fit 25mm battens???

 

[Deleted member 292770]

can we see it?