2. builder方认为这种裂缝属于正常地基沉降所造成，同小区住户提交的one year maintenance list上面也经常出现类似的裂缝，并且也在车库门附近的，他的解释是“the angle iron above the garage door is settling in with the load it is carrying”
3. builder方提到我们这种情况有可能在1年内再次出现，需要“touch these cracks up again on your one year list”
4. 如果结构工程师确认“these cracks are not structural”，builder方提出的整改方案是“chisel out the cracks and re-mortar them”
The lintel is strong enough to carry the load from the masonry, but the I value (second moment of area) is insufficient.
It is very common to see the mortar joint/masonry near the central or at third points (车库门宽度的3分之一）of the garage door width is cracked when the actual deflection of the lintel is greater than the allowable (permissible) deflection.
As a result, section of masonry near both ends of the lintel will get 'push' out.
In your case, there is a substantial masonry section on the right hand side reveal (blue circled in the attached).
The masonry section on the left is smaller than the right hand side and is 'pushed' by the end of the deflected lintel. Hence, the stepped cracks on the top left corner occurs.
You need a deeper lintel section (deeper means a bigger H - see attached below) with the I value is greater than the existing lintel to support the masonry above.
Note-
1) ensure wall ties to the external leave is provided (see attached) - wall ties to be stainless steel or galvanised (to avoid future corrosion)
2) new steel lintel to be hot-dip galvanised (to avoid future corrosion). Normally, the thickness of the steel lintel is approx. 6mm (1/4 in). Once is corroded (without the galvanised protecting coat), it expands and this will cause the mortar joints to cracks. Then, rain/water penetration will cause lots of issues like dampness to the timber frame structures. In a long run, decayed timber will cause wood rotten/fungi etc.
2）end bearing of the lintel is inadequate （see attached blue circled) - 一般建议是最少达到6" (150mm)
照片上的end bearing 差不多是3" (75mm)左右 - 明显是不达标的。
这个是施工团队的责任，因为the lintel has been built with poor workmanship and quality
Lintel has not been designed and checked acoordingly to the loads and cause excessive deflection - 这是设计团队的责任。很多时候（尤其是民宅），很多设计都是‘套用’以往、之前的设计方案，所以经常会忽略了这些细节。照片里lintel所支撑的墙体差不多有3尺（900mm左右)的高度 (fascia board 后面应该还有2-3 courses of brickwork)
从图里看，车库的宽度是21尺（6400mm)。
左侧的墙体估计是3尺左右，一般的停车位的最小规格要求是2400 宽 x 4800 长， 所以我估计双车库的门宽差不多是16尺（4800mm)左右。
原帖在此：https://bbs.wenxuecity.com/tzlc/1571939.html 非常感谢大家的意见和帮助！
今天晚上收到Builder那边的回复，大概可以归纳为如下几点：
1. 他们会找本地一家结构工程公司出具报告（早些时候问了我们的经纪人也是推荐同一家公司，说在本地口碑较好）
2. builder方认为这种裂缝属于正常地基沉降所造成，同小区住户提交的one year maintenance list上面也经常出现类似的裂缝，并且也在车库门附近的，他的解释是“the angle iron above the garage door is settling in with the load it is carrying”
3. builder方提到我们这种情况有可能在1年内再次出现，需要“touch these cracks up again on your one year list”
4. 如果结构工程师确认“these cracks are not structural”，builder方提出的整改方案是“chisel out the cracks and re-mortar them”
想请问大家，上面的这种解释和整改方案大家觉得合理吗？
对于下一步，我们暂定如下两个方案：
前提A：如果结构工程师出具的报告表示没有问题，那么我们除了要求延长保修期外还需要提什么要求吗？
前提B：如果结构工程师出具的报告表示有结构性问题，那么我们直接要求退回预付款和取消合同。不过从builder的口吻来看，出现结构性问题的可能性估计不大。
再次感谢大家，新年快乐！
我不是专家，但是房子还没盖好就有，不应该是正常的吧。
Support of Brick over Garage Doors - Bing video
只能说点儿自学的一点皮毛知识，用在选房子时帮助自己做大致判断。
通常，梯子型的砖裂缝，表示为沉降引起（水泥收缩为直线）。
砖贴面本身不承重，frame不够承重，不是地基问题，有没有设计或材料上的缺陷？
或许不是大问题，但先要找专家确认（最好由你方联系）。鉴于做工粗糙，又有裂缝，我认为重做这面砖贴面的要求不算过分，这个你的买房Agent可以去为你争取。
假如地基有问题，你考虑退出，拿回早期款有纷争时，找地产律师。
跟买车也一样试一下出现故障。你还买吗。除非大折扣
若structure engineer 能出具不是结构问题的报告，那么就放心买吧。就是不均匀沉降的问题，过几年就好了。
沉降影响的部分。
The lintel at the garage door head is sagging.
The lintel is strong enough to carry the load from the masonry, but the I value (second moment of area) is insufficient.
It is very common to see the mortar joint/masonry near the central or at third points (车库门宽度的3分之一）of the garage door width is cracked when the actual deflection of the lintel is greater than the allowable (permissible) deflection.
As a result, section of masonry near both ends of the lintel will get 'push' out.
In your case, there is a substantial masonry section on the right hand side reveal (blue circled in the attached).
The masonry section on the left is smaller than the right hand side and is 'pushed' by the end of the deflected lintel. Hence, the stepped cracks on the top left corner occurs.
You need a deeper lintel section (deeper means a bigger H - see attached below) with the I value is greater than the existing lintel to support the masonry above.
Note-
1) ensure wall ties to the external leave is provided (see attached) - wall ties to be stainless steel or galvanised (to avoid future corrosion)
2) new steel lintel to be hot-dip galvanised (to avoid future corrosion). Normally, the thickness of the steel lintel is approx. 6mm (1/4 in). Once is corroded (without the galvanised protecting coat), it expands and this will cause the mortar joints to cracks. Then, rain/water penetration will cause lots of issues like dampness to the timber frame structures. In a long run, decayed timber will cause wood rotten/fungi etc.
Hope this helps.
仔细再看了看照片，发现两样东西：
1）车库门中间上面的墙体应该是往里凹的 - 可以去home depot 买根48"的spirit level, 量一量就知道了
2）end bearing of the lintel is inadequate （see attached blue circled) - 一般建议是最少达到6" (150mm)
照片上的end bearing 差不多是3" (75mm)左右 - 明显是不达标的。
这个是施工团队的责任，因为the lintel has been built with poor workmanship and quality
Lintel has not been designed and checked acoordingly to the loads and cause excessive deflection - 这是设计团队的责任。很多时候（尤其是民宅），很多设计都是‘套用’以往、之前的设计方案，所以经常会忽略了这些细节。照片里lintel所支撑的墙体差不多有3尺（900mm左右)的高度 (fascia board 后面应该还有2-3 courses of brickwork)
从图里看，车库的宽度是21尺（6400mm)。
左侧的墙体估计是3尺左右，一般的停车位的最小规格要求是2400 宽 x 4800 长， 所以我估计双车库的门宽差不多是16尺（4800mm)左右。
新房的话，房子出现这种问题，不管怎么说，开发商、建筑商都有责任要提供维修 - 具体就看你怎么去谈判， 责任他们是跑不了了。