Screws through damp proof course.

[Keithj]

The lime render is now going onto the wooden laths on our "garden room" and looks excellent. The galvanised mesh was removed and the bags of cement have gone back whence they came. Good decision made there, with the help of the folks on here. Many thanks!

We have one remaining worry. The architect's drawing shows that the timber frame should be fixed to the brick plinth with metal brackets that run parallel, and inside. Those have been fitted.

HOWEVER ... when the wood frame was first installed (over the DPC above the bricks) it was screwed down to the bricks, straight through the DPC. I challenged this as I thought it would compromise the DPC. The builder assures me that the plastic plugs inserted into the brickwork will seal to the DPC and all will be well. The buildings inspector says it's not part of his remit to rule on screws through DPCs.

I'm not sure. Any views here? Is there anything that can be done now, anyway?

 

[Flyfisher]

How high is the brick plinth and is it likely that any damp will rise to the top of it anyway?

Even if any damp does rise to the top of the plinth and penetrates a few screw holes, won't it easily evaporate because of your wise choice to use lime render?

Even if any damp does rise to the top of the plinth and penetrates a few screw holes and doesn't quickly evaporate, how many hundred years will such damp take before it causes any appreciable problems to the timber frame (I'm assuming it's oak)?

How many historic properties have existed for hundreds of years with a timber frame sitting on a brick plinth with no DPC at all?

Sorry to ask so many questions instead of providing a definitive answer, but I suspect you'll have nothing to worry about in your lifetime.

 

[AMc]

I'm not sure. Any views here? Is there anything that can be done now, anyway?

I can't see how the two could be connected without some form of mechanical fixing. Assuming a plastic plug and a tight screw in it I wouldn't be that worried and given that there is almost nothing you could do now I would file that as something to try and forget about if I were you!

 

[Keithj]

Thank you. I am reassured in large measure. The timber structure above the DPC in the new build isn't oak, it's C16, whatever that is. The DPC above the brick is probably about two bricks higher than the ground level outside.

It seemed to me that if a DPC is specified by the architect and by "regs", it is needed for some fine purpose. However, I'll stop worrying now.

 

[Penners]

C16 is a strength grading classification for softwood. It's probably the most widely used grade for building work. It specifies the number of strength-reducing flaws in the wood - knots, shakes and so on - to within certain limits.

So it's not a measure of the timber's damp-resistance properties.

Was pre-treated timber used - tanalised or similar? If so, I really don't think a few screw-holes are anything to worry about. If you think about it, the dpc is actually lifting the timber clear of any contact it might have with the masonry below it (albeit only by a millimetre or so) as well as acting as a barrier to that damp. So the chance of damp rising into the sole plate by shinning up the shank of a screw (which is itself insulated from damp by the plastic plug) is so remote as to be, to all intents and purposes, non-existent.

I should relax and pour yourself a glass of something. :wink:

 

[middi]

No need to worry, relax. ( as Penners suggested)